Ngiri-1 was the first well to be drilled by Heritage Oil in Exploration Area 1 (EA 1) of Uganda. It was drilled as a vertical exploration well on the Ngiri (Warthog) structure and was suspended as an oil and gas discovery. The well was drilled in the North Albert Basin in EA 1, in the western part of the Republic of Uganda near the northern end of Lake Albert, approximately 6km east of Lake Albert and 4 km south of the Victoria Nile. It lies to the southwest of Paraa and the associated oil seep and outside of the Murchison Falls National Park area in Buliisa county of Buliisa district. It is approximately 11km south west and on trend with the subsequent Rii-1/Buffalo-1 discovery. The well was drilled as a vertical hole, situated at the intersection of 2D seismic dip line BW-09LD-33 and strike line HOG-B1-07-12.

The primary exploration objective was to drill and assess the potential of the Tertiary sandstones, in particular those associated with the Near Top Reservoir Seismic marker and associated amplitude anomaly predicted to be at 622m TVDBRT. The bottom of the objective was predicted at the Near Base Tertiary Seismic Marker at 853m TVDBRT with the well total depth (TD) estimated at 953m TVDBRT giving a logging sump within metamorphic basement.

The well was spudded on 27th September 2008 and drilled to a total depth (TD) of 911m MDBRT. The well was suspended as a potential future production well on the 29th October 2008.

Operations and results

Ngiri-1 was drilled as a vertical exploration well with a plan to perform coring. The Top Reservoir Seismic Marker was encountered at 618m MDBRT, 4m high to prognosis, with elevated gas levels seen from 617m MDBRT. From 621m MDBRT five six metre cores were cut at different intervals down to 773.5m MDBRT. Oil shows were seen from sandstones over the interval 620m to 632m MDBRT and 688m to 767.5m MDBRT; gas levels started to reduce from 769m MDBRT downwards with only ethane and methane being present below 799m MDBRT.

Petrophysical analysis of wireline logs and formation pressure data indicated that there is a gross hydrocarbon bearing interval of approximately 150m with net hydrocarbon pay of approximately 46m. 31m of net oil pay is calculated in the principal oil-bearing reservoir section, overlain by 15m of net gas pay.

RCI pressure testing and sampling confirmed the presence of moveable oil, which was recovered to surface, and both core analysis and log interpretation indicated reservoir quality in all pay zones to be excellent. The gross oil and gas intervals seen in the well were 83m and 67m respectively, with a calculated gas oil contact of 696.0m MDBRT and a calculated oil water contact of 768.6m MDBRT.

Jobi East-1 was the first exploration well to be drilled by Tullow Oil on the Jobi East structure. The structure is located in the Uganda Exploration Area 1, which is in the western part of the Republic of Uganda near the northern end of Lake Albert.

The Jobi East-1 prospect was identified on HOG-07-07, which forms part of the 2007 2D seismic dataset. The well is offset by the Jobi-1 well which is located 4 kilometers.

The well was drilled with the objective to test for the presence of hydrocarbons within the H15 to H30 sequences up-dip of the Jobi-1 well discovery, establish fluid contacts of any hydrocarbon columns encountered and assess communication with other offset wells, test the lateral extent of the sands, NTG distribution and connectivity, to flow test candidate with a separate testing program and work-over proposal to install the completion at a later date, to intersect basement in order to aid seismic tie over the Jobi East region and finally to obtain a much better understanding of the trapping mechanism at this location of the basin.

The well was spudded on 28th November 2008 and drilled as a vertical exploration well to a total depth of 637m MDBRT.

Operations and results

Jobi East-1 was drilled as a vertical exploration well in the Jobi East structure. The Top Reservoir Seismic Marker was encountered at 392.7m MDBRT, 54.7m low to prognosis, with elevated gas levels seen from this depth. Oil shows were seen from sandstones over the interval 421.1m MDBRT to 516.6m MDBRT; gas levels also reduced from this point on.

Jobi-East-2 (02N31E/91-3) well was drilled to appraise the Jobi-East-1 discovery. The Jobi-East-2 prospect was identified on HOG-07-05, which forms part of the sparse 2007 2D seismic dataset. The well was drilled to appraise the Jobi-East discovery which lies up-dip and to the east of the Jobi-Rii Field. The well was drilled to appraise the Jobi-East-1 discovery by testing for the presence of hydrocarbons within the H15 to H30 sequences, to intersect basement in order to aid seismic tie over the Jobi East region, to establish OWC of any hydrocarbon columns encountered and appraise communication with offset wells, in particular Jobi-East-1, to test the lateral extent of the sands, NTG distribution and connectivity and to core in a sidetrack, contingent upon reservoir evaluation of the pilot hole.

The well was spud on 27th August 2011 as a vertical appraisal well using OGEC RR600 rig to a total depth (TD) of 417m MDBRT. Subsequently, the well was plugged and abandoned for sidetracking.

Operations and results

Jobi East-2 was drilled as a vertical appraisal to appraise the Jobi East structure. A sidetrack was planned for coring. The top of the H30 in Jobi East-2 was encountered at 282m MDBRT and poorly developed in both Jobi East-2 and Jobi East-2A, with a net to gross of 0.22. Porosity over the reservoir interval was good, at 26%. The presence of hydrocarbons was confirmed by the capture of an oil sample at 286.2m MDBRT during the RCI run.

The H27 had a net to gross of 0.37 in JobiEast-2. Excellent porosity was encountered here, with an average between The H25 proved to contain the largest amount of hydrocarbons. Jobi East-2 had a pay count of 11.3m (SHF). Net to gross was excellent, with 0.88. Porosity was equally impressive, with an average across the reservoir zone of 36.6%.

H15 was penetrated and showed some excellent reservoir quality, with an average porosity between both wells of 31.4%. However, H15 was water bearing.

Jobi-East-2A (02N31E/91-3A) well was drilled as a sidetrack well for Jobi East-2 well to allow intervals of reservoir sands to be cored from data acquired in the pilot hole. The Jobi-East-2A was identified on HOG-07-05, which forms part of the sparse 2007 2D seismic dataset. The well was drilled to appraise the Jobi-East-1 discovery by testing for the presence of hydrocarbons within the H15 to H30 sequences, to intersect basement in order to aid seismic tie over the Jobi East region, to establish OWC of any hydrocarbon columns encountered and appraise communication with offset wells, in particular Jobi-East-1, to test the lateral extent of the sands, NTG distribution and connectivity and to core in a sidetrack, contingent upon reservoir evaluation of the pilot hole.

The well was spud on 10th September 2011 as a sidetrack well using OGEC RR600 rig to a total depth (TD) of 495m MDBRT on 28th September 2011.

Operations and results

Jobi East-2A was drilled as a sidetrack well for Jobi East-2 to allow intervals of reservoir sands to be cored. The top of the H30 in Jobi East-2A was encountered at 282m MDBRT. It was poorly developed with a net to gross of 0.13. The presence of hydrocarbons was confirmed by the capture of an oil sample at 286.2m MDBRT during the RCI run.

The H27 was better developed in Jobi East-2A, with a net to gross of 0.51 compared with 0.37 in Jobi East-2. Excellent porosity was encountered here, with an average of 32%. The H27 in Jobi East-2A consisted of both oil and gas. Oil was encountered at the top of the formation, down to 317m MDBRT.

The H25 proved to contain the largest amount of hydrocarbons. Net to gross was excellent, with 0.92 in Jobi East-2A. Porosity was equally impressive, with an average across the reservoir zone of 34.5%.

H15 was showed some excellent reservoir quality, with an average porosity of 31.4%. However, H15 was water bearing.

A total of Eight (8) cores were cut in Jobi East-2A and suspended for future re-entry.

Well Testing

Well testing was undertaken by Schlumberger on behalf of Total E&P Uganda. The well 02N31E/91-3A (Jobi East-2A) was re-entered the 02nd March by ZPEB Rig-26 to perform Well Test operation. The main purpose of the well is to appraise the undrilled Jobi field to determine permeability and skin of the productive interval, determine the existence of any near well bore reservoir heterogeneities and limits, determine the short-term productivity index of the well (transient PI) and also to determine Vertical interference between H27/H25.

Well was permanently abandoned the 19 April 2013 with three (3) cement plugs; cement plug#1 from 364.5m/RT to 200m/RT, cement plug#2 from 201m/RT to 24m/RT and cement plug#3 (top cement to surface).

Jobi East-3 (02N31E 91- 6) was planned as a vertical well to drill and appraise the up-dip extension of the Jobi-East Field. The well is situated onshore within the Murchison Falls National Park in the North Nile Area (~10 km to the North of Victoria Nile and ~9 km to the East from Albert Nile). The surface location is approximately 3 km Northeast of Jobi East-6, 4.7 km Northeast of Jobi East-1 and 3.5 km Southeast of Jobi East-2. Jobi East-3 is positioned at the intersection between 2D Regional Seismic lines HOG07-08.

The well main objectives were to drill and evaluate the presence of hydrocarbon bearing reservoirs in the Jobi East-3 panel, eastern up-dip of Jobi East-1 and Jobi East-6 panel, to evaluate the hydrocarbon nature (gas, oil, tarmat?) and quality and the fluid vertical connectivity between the different reservoir intervals, evaluate the quality and continuity of all reservoir intervals, assess the connection/disconnection with the other Jobi East panels, assess the cap rock integrity for very shallow reservoirs (geo-mechanics) and to assess the dynamic properties of the oil bearing sands intersected by the well.

Jobi East-3 was spudded on 3rd September 2013 with the OGEC RR600 rig and reached TD on 6th September 2013 at 254 m MD/RT inside the H1 Weathered Basement. The well was plugged back and sidetracked for selective coring.

Operations and results

Jobi East-3 (02N31E 91- 6) was drilled to appraise the up-dip extension of the Jobi-East Field. Due to the presence of hydrocarbons, the pilot hole was plugged back and sidetracked for selective coring. Jobi East-3 intersected all Mio-Pliocene reservoirs from Top H30 down to weathered basement (H1). Top H30 was encountered at 148.0 m MD/RT. Reservoirs facies represented by an alternation of unconsolidated sands with soft swelling clays and have moderate to fair petrophysical properties. Over all net sand thickness is 22.2 m with an average NTG of 25%. Oil shows have been described within the different reservoirs with impregnations varying depending on the reservoir quality.

H30 sands are relatively well developed (in term of thickness) in comparison with Jobi East-6 and Jobi East-1 but oil indications are poor.

If locally, a good oil sand (porosity >32 %) observed at the top of the H27, the other sands present in the H27 are generally poorer with porosity hardly above 20%. Massive sand observed within the H27L but with minor oil indications while drilling. According to log interpretation, this H27L sand appears argillaceous and water bearing. All MDT attempts made in the H27 were tights or lost seals.

A good oil bearing sand (porosity > 30 %, Soil average of 77 %) is encountered at the base of the H25 with an ODT at 219 m MD/RT.

Below H25, reservoirs development is generally poor and limited within the H15. All sands encountered between H17 and H1 appear water bearing.

Jobi-East-3A (02N31E/91-6A) well was drilled as a sidetrack well for Jobi East-3 for selective coring. The well is situated onshore within the Murchison Falls National Park in the North Nile Area (~10 km to the North of Victoria Nile and ~9 km to the East from Albert Nile). The surface location is approximately 3 km Northeast of Jobi East-6, 4.7 km Northeast of Jobi East-1 and 3.5 km Southeast of Jobi East-2. Jobi East-3 is positioned at the intersection between 2D Regional Seismic lines HOG07-08.

The well main objectives were to drill and evaluate the presence of hydrocarbon bearing reservoirs in the Jobi East-3 panel, eastern up-dip of Jobi East-1 and Jobi East-6 panel, to evaluate the hydrocarbon nature (gas, oil, tarmat?) and quality and the fluid vertical connectivity between the different reservoir intervals, evaluate the quality and continuity of all reservoir intervals, assess the connection/disconnection with the other Jobi East panels, assess the cap rock integrity for very shallow reservoirs (geo-mechanics) and to assess the dynamic properties of the oil bearing sands intersected by the well.

Jobi-East-3A was drilled to a final TD of 254.0 m MD/RT reached on 13th September 2013, logged and subsequently prepared for testing in the H25.

Operations and results

Jobi East-3A (02N31E 91- 6A) was drilled as a sidetrack for selective coring of the Jobi East-3. The first hydrocarbon shows were encountered from the top of the H30; no shows were seen above this zone. Multiple hydrocarbon shows were observed while coring.

Well Testing

One production and one injection test were performed on H25 reservoir from 29th September to 1st October, 2013.The well was perforated from 216 to 219 m MD/RT. The well was produced with PCP. A flowrate of 1.8 m3/d was achieved with 14.9 bars of draw down. It was followed by 100 hours of build-up. A bottom hole sampling was performed with wire-line. 2 SRS bottles were run but only one was filled.

The injection test was performed in 3 phases. First, 20 cp viscosified water was injected for the mini-frac sequence. It was then followed by an isochronal injection/fall-off period with 20 cp viscosified water. Then fresh water was injected in 3 additional injection/fall-off steps.

Jobi East-4 was planned as a vertical well to drill and appraise the presence of hydrocarbon in the Jobi East-4 eastern panel up-dip of Jobi East-3. The well is situated on land within the Murchison Falls National Park in the North Nile Area (~4.9 km to the North of Victoria Nile and ~11.2 km to the East of Albert Nile). The surface location is approximately 2.4 km SE of Jobi East-7, 4.8 km NE of Jobi East-5 and 2.4 km NW of Mpyo-2. Jobi East-4 is positioned on 2D Regional Seismic line HOG07-07 (Fugro processed Final PSTM dataset, shot point: 2379, CMP-501, Trace-500).

The main pre-well objectives were to drill and evaluate the presence of hydrocarbon bearing reservoirs in the Jobi East-4 panel, eastern up-dip of Jobi East-3 panel, evaluate the hydrocarbon nature (gas, oil, tarmat ?) and quality and the fluid vertical connectivity between the different reservoir intervals, evaluate the quality and continuity of all the reservoir intervals and to assess the connection/disconnection with the other Jobi East panels.

Jobi East-4 was spudded on 12th October 2013 with the rig OGEC RR600 and the well reached TD at 235 m MD/RT inside the H1 weathered basement on 15th October 2013. The well was neither sidetracked or tested. The well was plugged and abandoned subsequently to the wireline logging operations.

Operations and results

Jobi East-4 was planned as a vertical well to appraise the presence of hydrocarbon in the Jobi East-4 eastern panel up-dip of Jobi East-3. The well intersected all Mio-Pliocene reservoirs from Top H30 down to weathered basement (H1). Top H30 was encountered at 116.0 m MD/RT.

Reservoirs facies is represented by an alternation of unconsolidated sands with soft swelling clays and have moderate to fair petrophysical properties. Over all net sand thickness within reservoir intervals is 25m with an average NTG of 25%.

H30 is relatively compact represented by argillaceous fine sands with minor HC impregnation. No significant HC charging is observed from resistivity logs and MDT measurements though gas and oil shows were observed during drilling.

H27 is hydrocarbon bearing with minor gas cap of 2.5 m at the top. H27 reservoir facies is well developed with good reservoir characteristics of PhiE of ~27% with SHC of ~50%.

Section from top H25 down to weathered basement H1 is dominantly argillaceous lacking any reservoir facies for hydrocarbon charge.

Jobi East-5 well location lies within the Victoria Nile Delta Play which is dominantly a fluvial/lacustrine-deltaic environment. The Jobi-East-5 was identified on HOG-07-09, which forms part of the sparse 2007 2D seismic. The well was drilled second in the Jobi East sequence, and tested the extension of the amplitude supported Jobi East field which lies to the east of the Jobi-Rii Field. The offset well Jobi-1 is located 2.4km southwest of the Jobi-East-1 well.

The objectives for Jobi-East-5 were to test for the presence of hydrocarbons within the H15 to H30 sequences 5km to the south of Jobi East-1 well discovery, to intersect basement in order to aid seismic tie over the Jobi East region, to test the lateral extent of the sands, NTG distribution and connectivity, to flow testing candidate with a separate testing program and work-over proposal to install the completion at a later date, to test for compartmentalization in the Jobi-East field, to establish OWCs of any hydrocarbon columns encountered and assess communication with offset wells and coring in sidetrack was contingent on reservoir evaluation of the pilot hole.

Jobi East-5 was planned and drilled by Tullow Uganda Operations Ltd as an appraisal well spudded on 13th July 2011 with OGEC IRI 600 rig. The well drilled to basement and reached a total depth of 625m MDBRT on 30th July 2011. Subsequently, the pilot hole was plugged and sidetracked after logging.

Operations and results

Jobi-East-5 was to test for the presence of hydrocarbons within the H15 to H30 sequences. However, all reservoirs were fully water bearing. Very good sand development with excellent reservoir quality was encountered. The H30 had a net to reservoir interval of 0.42, with an average porosity of 31%. Again, reservoir quality in the H27 was excellent, with average porosities of 35.5% and a net to reservoir interval of 0.47.

Jobi East-5A(02N31E/103-4A) well location lies within the Victoria Nile Delta Play which is dominantly a fluvial/lacustrine-deltaic environment. The Jobi-East-5A was identified on HOG-07-09, which forms part of the sparse 2007 2D seismic. The well was drilled on the Jobi East sequence, and tested the extension of the amplitude supported Jobi East field which lies to the east of the Jobi-Rii Field. The offset well Jobi-1 is located 2.4km southwest of the Jobi-East-1 well.

The objectives for Jobi-East-5A were to test for the presence of hydrocarbons within the H15 to H30 sequences 5km to the south of Jobi East-1 well discovery, to intersect basement in order to aid seismic tie over the Jobi East region, to test the lateral extent of the sands, NTG distribution and connectivity, to flow testing candidate with a separate testing program and work-over proposal to install the completion at a later date, to test for compartmentalization in the Jobi-East field, to establish OWCs of any hydrocarbon columns encountered and assess communication with offset wells and coring in sidetrack was contingent on reservoir evaluation of the pilot hole.

Jobi East-5A was planned as deviated sidetrack appraisal for Jobi East-5 drilled by Tullow Uganda Operations Ltd with OGEC IRI 600 rig. The sidetrack was kicked off on 7th August 2011 and reached a total depth of 675m MDBRT on 14th August 2011.

Operations and results

Jobi-East-5A was to test for the presence of hydrocarbons within the H15 to H30 sequences. However, all reservoirs were fully water bearing as similarly observed in Jobi East-5 pilot hole. Very good sand development with excellent reservoir quality was encountered. A basic logging suite was run over the sidetrack.

Jobi East-6 (02N31E 91-4) was planned as a vertical well to drill and appraise the up-dip extension of the proven panel discovered by Jobi East-1 in May 2011. The well is situated onshore within the Murchison Falls National Park in the North Nile Area (~10 km to the North of Victoria Nile and ~6 km to the East from Albert Nile). The surface location is approximately 1.8 km NE of Jobi East-1, 3.2 km SSE of Jobi East-2 and 6.8 km South-South-West of Lyec-1. Jobi East-6 was positioned on 2D Regional Seismic line HOG07-08 (Fugro processed PSTM dataset, shot point-414, CMP-1394, trace-1393).

Jobi East-6 pre-well objectives were to appraise the up-dip extension of Jobi East-1 panel to the North of Jobi East-1 discovery, to assess the possible connection with the Jobi East-1 panel, to assess the possible gas column in H27, to evaluate the reservoir quality and assess the hydrocarbon vertical connectivity, to evaluate the oil quality, to evaluate the top seal efficiency and to assess the dynamic properties of the oil bearing reservoirs.

Jobi East-6 was spudded on 14th July 2013 with rig Caroil 2 reachin a total depth (TD) at 427 m MD/RT inside the H1 Weathered Basement on 23rd July 2013. The well was subsequently plugged for sidetracking to perform selective coring.

Operations and results

Jobi East-6 was planned as a vertical well to drill and appraise the up-dip extension of the proven panel discovered by Jobi East-1 in May 2011. On drilling, Jobi East-6 intersected all Mio-Pliocene reservoirs from Top H30 down to weathered basement (H1). Top H30 was encountered at 256.1 m MD/RT, that is 0.7 meter deeper than prognosis.

Reservoirs have fair to high petrophysical properties. The best porosity is encountered in H27 reservoir (28%). H30 is poorly developed. Reservoirs H30 to H15 included were encountered oil-bearing with an ODT in H15 at 353 m MD/RT.

MDT pressure pretests show reasonable alignment with Jobi-east-1 data in H27 and H25 levels that seem to be in communication and share a common FWL at around -334 m TVDLL.

Jobi East-6A (02N31E 91-4A) was planned as a sidetrack to Jobi East-6 for selective coring. The well is situated onshore within the Murchison Falls National Park in the North Nile Area (~10 km to the North of Victoria Nile and ~6 km to the East from Albert Nile). The surface location is approximately 1.8 km NE of Jobi East-1, 3.2 km SSE of Jobi East-2 and 6.8 km South-South-West of Lyec-1. Jobi East-6 was positioned on 2D Regional Seismic line HOG07-08 (Fugro processed PSTM dataset, shot point-414, CMP-1394, trace-1393).

The objectives of the well were to appraise the up-dip extension of Jobi East 1 panel to the north of Jobi East 1 discovery, assess possible gas column in H27, assess reservoirs quality and assess hydrocarbon connectivity and evaluate the oil quality

Due to the presence of hydrocarbons in Jobi East-6, the pilot hole was plugged back and sidetracked to Jobi East-6A from 215 m MD/RT, with a selective coring operation being carried out in the hydrocarbon reservoirs. The sidetrack was drilled to a final total depth (TD) of 434.0 m MD/RT. A number of 12 cores were cut from the sidetrack borehole. No sidewall cores were taken. The well was equipped with 7” casing and ready for testing on 9th August 2013.

Operations and results

Jobi East-6A was drilled as a sidetrack for selective coring at Jobi East-6. A total number of 12 cores were recovered from the sidetrack. Jobi East-6A intersected all Mio-Pliocene reservoirs from Top H30 down to weathered basement (H1). Top H30 was encountered at 256.1 m MD/RT, that is 0.7 meter deeper than prognosis.

The reservoirs have fair to high petrophysical properties. The best porosity encountered in H27 reservoir (28%) and H30 poorly developed.

Reservoirs H30 to H15 encountered oil-bearing with an ODT in H15 at 353 m MD/RT. MDT pressure pretests show reasonable alignment with Jobi-east-1 data in H27 and H25 levels that seem to be in communication and share a common FWL at around -334 m TVDLL.

Oil samples were recovered in H25 and H27.

Well Testing

A production test, bottom hole sampling with wire-line and injection tests (mini-frac and isochronal sequence with viscosified water then fresh water) were successfully performed in H25.

The same test sequence was also carried out in H27. Production and injection tests were successful, but wireline bottom hole sampling failed.

The following oil bearing zones were tested at Jobi East 6A (02N31E/91-4A):

• The H25 sand: 318.0 – 326.5m MD/RT
• The H27 sand: 295.0 - 311.5m MD/RT

Jobi East-7 was planned as a vertical well to drill and appraise the presence of hydrocarbon up-dip of Jobi East-5 and 5A dry wells. The well is situated on land within the Murchison Falls National Park in the North Nile Area (~6.2 km to the North of Victoria Nile and ~6.8 km to the East of Albert Nile). The surface location is approximately 4.4 km North East of Jobi East-5/-5A, 1.9 km South East of Jobi East-1, 5.6 km South South East of Jobi East-2 and 9 km South of Lyec-1. Jobi East-7 is positioned on 2D Regional Seismic line HOG07-07 Fugro processed Final PSTM dataset, shot point-2457, CMP-341, trace-340).

The main pre-well objectives were to drill and evaluate the presence of hydrocarbon bearing reservoirs in the panel up-dip of Jobi East-5/-5A wells, to assess the reservoir and hydrocarbon nature and quality within that panel, to assess the connection/disconnection with the Jobi East-1 panel, to evaluate the fluid vertical connectivity between the different reservoirs and to evaluate the top seal efficiency.

Jobi East-7 was spudded on the 29th July 2013 with the OGEC RR600 rig, and the well reached final total depth (TD) at 440 m MD/RT on 5th August 2013. The well was subsequently plugged for sidetracking to perform selective coring.

Operations and results

Jobi East-7 was planned as a vertical well to drill and appraise the presence of hydrocarbon up-dip of Jobi East-5 and 5A dry wells. The well intersected all Mio-Pliocene reservoirs from Top H30 down to H1, altered basement. Top H30 was found at 298.2 m MD/RT, that is 12.7 meters deeper than prognosis. The reservoirs are an alternation of unconsolidated sands with soft swelling claystone.

Reservoirs have fair to high petrophysical properties. Very good porosity is encountered in both H25 and H27 reservoirs (~27%). Weak oil shows were evidenced while drilling in the H30 but further logging operations did not confirm any substantial oil accumulation. Reservoirs H27 to H25 included were encountered oil-bearing with an ODT at the base of H25 sand at 365.7m MD/RT. Reservoirs H15 down to top weathered basement (H1) are encountered water bearing, with a WUT in H15 top sand at 377.8 m MD/RT.

The Jobi-East-7 H30 pressure data show a possible connection with JobiEast-5/-5A H30 aquifer trend. A reasonable alignment of the MDT pressure points in H27 and H25 reservoirs show that these levels are probably in communication and share a common FWL at around -300 m TVD/LL. This FWL is compatible with the WUT observed in the H27 of Jobi-East-5A in a downdip position in the same panel. The Jobi-East-7/7A H27-H25 oil column interpreted on pressure plot is apparently not in communication with the Jobi-East-1/ Jobi-East -6 H27/H25 oil accumulations.

Jobi East-7A was planned as a sidetrack to Jobi East-7 for selective coring after confirmation of hydrocarbons. The well is situated on land within the Murchison Falls National Park in the North Nile Area (~6.2 km to the North of Victoria Nile and ~6.8 km to the East of Albert Nile). The surface location is approximately 4.4 km North East of Jobi East-5/-5A, 1.9 km South East of Jobi East-1, 5.6 km South South East of Jobi East-2 and 9 km South of Lyec-1. Jobi East-7 is positioned on 2D Regional Seismic line HOG07-07 Fugro processed Final PSTM dataset, shot point-2457, CMP-341, trace-340).

The main pre-well objectives were to drill and evaluate the presence of hydrocarbon bearing reservoirs in the panel up-dip of Jobi East-5/-5A wells, to assess the reservoir and hydrocarbon nature and quality within that panel, to assess the connection/disconnection with the Jobi East-1 panel, to evaluate the fluid vertical connectivity between the different reservoirs and to evaluate the top seal efficiency.

Jobi East-7A well was drilled as a sidetrack well for selective coring. Jobi East-7A was drilled from 243 m MD/RT to a final total depth (TD) of 444 m MD/RT reached on 17th August 2013. A number of 10 (ten) cores were cut in H33, H30, H27 and H25, for a total cored length of 23.6 meters (recovery 69%). The well was permanently abandoned with cement up to surface.

Operations and results

The Jobi East-7A sidetrack well was drilled as a sidetrack for Jobi East-7. The well intersected all Mio-Pliocene reservoirs from Top H30 down to H1, altered basement. Top H30 was found at 298.2 m MD/RT, that is 12.7 meters deeper than prognosis. The reservoirs are an alternation of unconsolidated sands with soft swelling claystone. The reservoirs have fair to high petrophysical properties. Very good porosity is encountered in both H25 and H27 reservoirs (~27%) The Jobi-East-7/7A H27-H25 oil column interpreted on pressure plot is apparently not in communication with the Jobi-East-1/-6 H27/H25 oil accumulation.

A number of 10 (ten) cores were cut in H33, H30, H27 and H25, for a total cored length of 23.6 meters (recovery 69%).

Jobi-1 well was drilled by Heritage Oil and Gas Limited on the neighbouring Jobi and Rii prospects, in the North Albert Basin of the EA 1. This is in the western part of the Republic of Uganda at the northern end of Lake Albert approximately 6 km east of the shoreline and to the north of the Victoria Nile. They lie to the west of Paraa and the associated oil seep; within the Murchison Falls National Park area in Nwoya County of Amaru district approximately 13 km north east of Ngiri-1.

The well is situated along the 2D seismic strike line HOG-B1-07-12 with Jobi-1 at the intersection of dip line HOG-B1-07-09.

The primary exploration objective was to drill and assess the potential of the Tertiary sandstones, in particular those associated with and below the Near Top Reservoir Seismic marker and associated amplitude anomaly predicted to be at 334m TVDBRT.

Jobi-1 was spudded on 28th November 2008 and drilled to a final total depth of 637m. The well was suspended as a potential future production well on 13th December 2008.

Operations and results

Jobi-1 was drilled as an exploration well on the Jobi/Rii prospect. The Top Reservoir Seismic Marker was encountered at 392.7m MDBRT, 54.7m low to prognosis, with elevated gas levels seen from this depth. Oil shows were seen from sandstones over the interval 421.1m to 516.6m MDBRT; gas levels also reduced from this point on.

Petrophysical analysis of wireline logs and formation pressure data indicated that there was a gross hydrocarbon-bearing interval of 123.1m from 392.5m with a net hydrocarbon pay of 47.7m. Of this 47.7m net pay interval, 28.5m of net oil pay calculated in the principal oil-bearing reservoir section, overlain by 19.2m of net gas pay. RCI pressure testing and sampling has confirmed the presence of moveable hydrocarbons, with both oil and gas having been recovered to surface. Wireline log interpretation indicates reservoir quality in all pay zones to be excellent. The gross oil and gas intervals seen in the well are 75.2m and 47.9m respectively, with a gas oil contact (GOC) of 440.4m; oil down to (ODT) 515.7m and a calculated oil water contact (OWC) of 582.8m (-133m TVDSS).

Jobi-2 was planned and drilled by Tullow as the third well on the Jobi/Rii structure as the first appraisal well. The well is located in an area of the field that has some depth uncertainty in the northern part of the field. Jobi-2 well location lies within the Victoria Nile Delta Play which is dominantly a fluvial/lacustrine-deltaic environment of deposition. The well was to reduce depth uncertainty in the northern part of the field, to establish Oil Water Contacts of any hydrocarbon columns encountered and assess communication with offset wells, to test the lateral extent of reservoir sands, NTG, distribution and connectivity, to carry out fluid sampling and evaluate the formation Kh, to flow test candidate with a separate testing programme and work-over proposal to install completion at a later date, to intersect Basement in order to aid seismic tie and to evaluate the fracture network with image logs and to extensively core the reservoir section and top seal.

The well was spudded on 1st June, 2011as a vertical well to final total depth of 590mBRT using OGEC RR600 rig and wireline log run before it was plugged back for sidetracking. Three cement plugs were set to isolate the bottom.

Operations and results

Jobi-2 was drilled to a final total depth (TD) of 590m. 2 Logging runs were complete, run 1A comprised of SGR/ZDEN/CN/HDIL. Run 1B was formed of GR/RCI, with 18 good tests, and 3 seal failures. During run 1B, oil samples were acquired at 443.7m and 475.4m. A water sample was taken at 482.7m. Jobi-2 was plugged back and sidetracked to Jobi-2A for coring.

Jobi-2A was planned and drilled by Tullow as a sidetrack well for Jobi-2 for coring purposes. The well is located in an area of the field that has some depth uncertainty in the northern part of the field. Jobi-2 well location lies within the Victoria Nile Delta Play which is dominantly a fluvial/lacustrine-deltaic environment of deposition. The well was to reduce depth uncertainty in the northern part of the field, to establish Oil Water Contacts of any hydrocarbon columns encountered and assess communication with offset wells, to test the lateral extent of reservoir sands, NTG, distribution and connectivity, to carry out fluid sampling and evaluate the formation Kh, to flow test candidate with a separate testing program and work-over proposal to install completion at a later date, to intersect Basement in order to aid seismic tie and to evaluate the fracture network with image logs and to extensively core the reservoir section and top seal.

The well reached total depth on 27th June 2011 using OGEC RR600 rig. A total of nine cores were cut before drilling the well to 671.5 mBRT (TD), about 25m into basement. Wireline logs were then run. The hole was plugged back to 598m and a 7’’ production casing set at 596m. Later well was tested using a separate program by Total E&P Uganda.

Operations and results

Jobi-2A was drilled as a sidetrack for Jobi-2 for coring purposes. A total of nine (9) cores were cut before the well reached total depth and wireline logging performed.

The H30 was encountered 11 meters shallower to prognosis. Average porosity over the reservoir interval here was 28.5%. Archie calculations gave a pay count of 2m compared to the SHF which had 4.1m. This was due to the thin bedded sands being beyond the vertical resolution of the resistivity tool, which the SHF was able to capture much better. An oil sample was obtained here on the RCI at 443.7m.

H27 contained both oil and water sands. A pay count of 4.8m (Archie) and 5.9m (SHF) was calculated. Average porosity over the reservoir interval was 34.7%. Average Sw over the oil zone was 45.8% (Archie) and 36.2% (SHF). The analysis was further verified by an oil sample taken at 475.4m from the RCI tool.

The H25 did have some good reservoir quality sands, these were however water bearing. 16.1m of reservoir quality sands were seen in the H15, giving a net reservoir to gross interval of 0.43. Porosity was excellent, with an average of 32%. Very little irreducible fluid was seen on the MREX tool over this interval, along with minimal amounts of clay.

Generally calculated permeabilities were very good, commonly over a 1 Darcy in the reservoir sands.

Well Testing

Well testing operations began on 16th February 2013 using the EXALO Rig 115 (formerly OGEC RR600). Two Production Tests (H27U and H30), 1 Injection Test and Fall-Off Test (H27U) were done by Schlumberger before the well was plugged and abandoned.

H27U and H30 objectives were productivity Index; KH, Skin (mechanical & global), identify heterogeneities near wellbore, determine minimum connected volume to the well, assess Kv/Kh on H27U layer and to take samples for flow assurance and PEPD.

H27U objectives were to plot BHFP vs Qinj curve in matrix regime, to assess injectivity index with polymers as the Enhanced Oil Recovery(EOR) plan and to assess injectivity index with fresh water.

The perforated intervals for H27U: 470-474 m MDRT and H30: 442-445.5 m MDRT by applying pressure to the test string. The well was then permanently plugged and abandoned with cement plugs after well testing operations.

The Jobi-3 well is a vertical appraisal well drilled by Total E&P Uganda in the middle of the central panel of the Jobi-Rii Field structure in Ugandan Exploration Area 1 (EA1). It was drilled in the middle of the central panel of the Jobi-Rii field structure in Ugandan Exploration Area 1. The well is located onshore, to the north of the Victoria Nile within the Murchison Falls National Park. It is situated on the 2D seismic section HOG07-12 (shot point 1689) between offset wells Jobi-1, 3.3 km to the north-east, and Rii-1, 2.2 km to the south-west.

The main purpose of the Jobi-3 well were to appraise the Jobi-Rii Field oil bearing reservoirs in the middle of the Central Panel. The other objectives were to assess reservoir quality, facies analysis, and dynamic properties of the H30, H27, H25 and H15 reservoirs through logging and coring, to evaluate connectivity within and between the 4 reservoir units (both vertically and laterally with other wells), to perform 3 production tests and 1 injection test (at a later stage in 2013), to core and characterize top seal to determine the upper injection pressure limit in the reservoir and to core and characterize the basement to assess a cuttings reinjection option during the development phase.

The well was spudded on 4th June 2012 as a vertical well to a final total depth of 626m on 24th July 2012 using OGEC RR600 rig.

Operations and results

The well targeted 4 oil bearing reservoirs (H30, H27, H25 and H15), within the Upper Pliocene interval, containing lacustrine and interbedded fluvial sands and claystone units. The fluid was similar to that of the offset wells, i.e. medium viscosity oil. The fluid was similar to that of the offset wells, i.e. medium viscosity oil.

The Jobi-3 vertical well intersected all Miocene to Pliocene reservoirs from Top H30 down to virgin basement (H0); Top H30 was found at 416 m MD/RT. The well TD was reached 30 metres within the basement (top H0) at 625 m MD/RT. The reservoirs are an alternation of unconsolidated sands with soft swelling claystones.

An important acquisition program was performed on this well this included a continuous coring. More than a hundred metres of core were continuously cut from top seal to top of water leg. Important issues with early jamming due to swelling clays led to cut a total of 33 cores. The recovery was 67%. In addition to the conventional logs necessary for formation evaluation, mineral spectroscopy and magnetic resonance were run to solve the uncertainties on reservoir properties. A VSP was recorded in each section for accurate seismic calibration of the first wells. Successful recording of VSP behind casing and in look-ahead led to lightening the VSP program on next wells. The straddle packer was run to record mini-DST in reservoir and ELOT in the top seal. After 2 runs with several attempts to maintain the seal and to achieve a flowrate, no miniDST was recordable. Only the Extended Leak-Off Test in the top seal was performed.

The main results are outlined as follows: H30-H15: oil bearing, H14: oil and water bearing (OWC at -485 m TVD/LL) and H1- H0: water bearing.

The well was temporarily suspended with a 7” casing in front of the oil reservoirs. 3 production and 1 injection tests which will help to evaluate the reservoir properties and their connectivity are planned to be performed in January 2013.

Well Testing

Well testing operations began on 2nd January 2013 using the rig OGEC RR600. 3 Production Tests (H15U, H25 and H27U), 1 Injection Test + Fall-Off Test (H27U) and 1 Vertical Interference Test (H15U/H25) were done before the well was permanently plugged and abandoned.

Injection Test objectives were to plot BHFP vs Qinj curve in matrix regime, to assess injectivity with polymers, to assess if pseudo-fracturing of the sands can be triggered prior to fracturing of the cap rock and to plot BHFP vs Qinj curve in pseudo-frac regime.

The vertical interference test objectives (H25 – H15U) was to characterize the communication between H25 (producer) and H15U (observer).

Well Test Operations Summary

• 3 production tests on H15U, H25 and H27U.
• 1 injection test + Fall-Off test on H27U.
• 1 vertical interference test on H15U/H25.

Perforated interval:

• H15U: 516-535 m MDRT.
• TCP #2 H25: 489.5-495.5 m MDRT.
• TCP #3 H27U: 456-465 m MDRT.

The Jobi-4 well was planned as a vertical appraisal well drilled in the North-west Panel of the Jobi-Rii Field structure in Ugandan Exploration Area 1 (EA1). The well is located on land, to the north of the Victoria Nile within the Murchison Falls National Park. It is situated on the 2D seismic section HOG-2010-05 (shot point 2116). The offset wells Jobi-1, 2.2 km to the south-east, and Jobi-2, 2.9 km to the north-east.

The main purpose of the Jobi-4 well was to appraise the North-West Panel of the Jobi-Rii Field. The pre-well objectives were to assess reservoir quality, facies analysis, and dynamic properties of the H30, H27, H25 and H15 reservoirs in the North-west Panel through logging and coring, to evaluate connectivity within and between the 4 reservoir units, and laterally with the Central Panel; and perform 1 production test in the H27 reservoir.

Jobi-4 well was spud on 05th August 2012 with the OGEC RR600 rig, and the well reached final total depth (TD) on 25th August 2012.

Operations and results

Jobi-4 was drilled as a vertical appraisal well targeting four (4) oil bearing reservoirs (H30, H27, H25 and H15), within the Upper Pliocene interval, containing lacustrine and interbedded fluvial sands and claystone units. The fluid was similar to that of the offset wells, i.e. medium viscosity oil.

The well intersected the Upper Pliocene reservoirs from Top H30 down to lower H14. Top H30 was found at 489.2 m MD/RT. The well TD was reached in the H14 formation at 668.8 m MD/RT. The reservoirs are an alternation of unconsolidated sands with soft swelling claystones.

An important acquisition program was performed on this well where approximately 32 m of selective cores was cut in the main reservoir intervals H30, H27 and H25. The average recovery was around 74%. In addition to the conventional logs necessary for formation evaluation, mineral spectroscopy and magnetic resonance logs were also run to help solve the uncertainty on reservoir properties. A zero-offset VSP log was also recorded after well TD for accurate seismic calibration of the first wells, and to reduce seismic uncertainty. Wireline formation tester for reservoir pressures and fluid sampling; and sidewall coring acquisition was also performed.

The main results were H30-H27: oil bearing, H25: oil and water bearing and H14-TD: water bearing.

Well Testing

A single well production test was performed in the H27U reservoir to better estimate the reservoir connectivity and production capacity.

The well test objectives were to assess skin, near-wellbore Kh, Kv/Kh and transitory (short term) productivity index of the well, to rule on the existence of heterogeneities in the well vicinity: structural and/or sedimentary limits, lateral facies variations, contacts, to estimate the oil volume connected to the well, to confront Kv/Kh value estimated from H27U classical test interpretation with Kv/kh value obtained from extended H27L RCI pretest interpretation.

The well was then permanently abandoned with cement plugs.

Jobi-5 well is an appraisal well drilled in the middle of the Central Panel of the Jobi-Rii Field structure in Ugandan Exploration Area 1 (EA1). The well is located on land, in the Paraa Discovery area (EA1), to the North of the Victoria Nile within the Murchison Falls National Park. It is situated on the 2D seismic section HOG-2010-06 (shot point 1669) with offset wells Jobi-1 ~2.0 km to the East, Jobi-3 ~2.5 km to the South, and Jobi-4 ~2.5 km to the North-East.

The main purpose of the Jobi-5 well was to appraise the Jobi Field oil bearing reservoirs in the middle of the western flank of the central panel. The other objectives were to assess reservoir quality, facies control, and dynamic properties of the H30, H27, H25 and H15 reservoirs and of weathered basement through logging and selective coring in the sidetrack Jobi-5A, to confirm Oil-Water Contact of the Central Panel, to obtain dynamic properties in the Central Panel, to evaluate connectivity between the reservoirs (both laterally and vertically) and to perform water injection test in H25 water leg.

Jobi-5 well was spudded on 3rd October 2012 with the OGEC RR600 rig. It reached the planned final total depth (TD) at 703.9 m MD in the H1 on the 11th October 2012. The pilot hole was plugged back inside 9 5/8” casing to allow a sidetrack enabling selective coring of the reservoirs.

Operations and results

The well was planned to target 3 oil bearing reservoirs (H30, H27, and H25 Upper) located within the lacustrine and fluvial sands units of the Mio-Pliocene series of the Albertine Rift. The fluid was similar to that of the offset wells, i.e. medium viscosity oil. The Jobi-5 vertical pilot hole intersected the reservoirs from Top H30 to lower H1 weathered basement. The main objectives of this well were achieved. The main results were reservoir intervals to TD i.e. H30: oil bearing, H27: oil and water bearing: Oil Down To [ODT] 571.5m MD/RT and H25- H1: water bearing.

Pressure gradient from wire-line tester proves a good connectivity with surrounding wells and consistency in the FWL in the central panel. An oil sample was also recovered in H27.

Jobi-5A well was planned as a sidetrack well for Jobi-5 for selective coring in the Central Panel of the Jobi-Rii Field structure in Ugandan Exploration Area 1 (EA1). The well is located on land, in the Paraa Discovery area (EA1), to the North of the Victoria Nile within the Murchison Falls National Park. It is situated on the 2D seismic section HOG-2010-06 (shot point 1669) with offset wells Jobi-1 ~2.0 km to the East, Jobi-3 ~2.5 km to the South, and Jobi-4 ~2.5 km to the North-East.

The main purpose of the Jobi-5 well was to appraise the Jobi Field oil bearing reservoirs in the middle of the western flank of the central panel. The other objectives were to assess reservoir quality, facies control, and dynamic properties of the H30, H27, H25 and H15 reservoirs and of weathered basement through logging and selective coring in the sidetrack Jobi-5A, to confirm Oil-Water Contact of the Central Panel, to obtain dynamic properties in the Central Panel, to evaluate connectivity between the reservoirs (both laterally and vertically) and to perform water injection test in H25 water leg.

Jobi-5A sidetrack was initiated from 416.5m MD/RT and following the coring operations TD was reached on 26th October 2012 at 703.6m MD/RT.

Operations and results

The well was planned to target 3 oil bearing reservoirs (H30, H27, and H25 Upper) located within the lacustrine and fluvial sands units of the Mio-Pliocene series of the Albertine Rift. The fluid was similar to that of the offset wells, i.e. medium viscosity oil.

Jobi-5A sidetracked the pilot hole mid-way through the H35 interval with the following results; Top H30 was found at 505.7m MD/RT in the sidetrack, Final well TD was reached in the H1 formation at 703.6 m MD/RT. The reservoirs are an alternation of unconsolidated sands with soft swelling claystones.

A length of 16 m of selective cores were cut (recovered) including 3 m in the cap-rock, 11 m in the main reservoir intervals H30 and H27, 2 m in the H1 weathered basement interval. Average recovery was 68.6%.

In addition to the conventional logs necessary for formation evaluation, mineral spectroscopy and magnetic resonance, simultaneous acoustic and resistivity imager logs were also run to help solve the uncertainty on reservoir properties. A zero-offset VSP log was recorded after well TD for accurate seismic calibration of the first wells, and to reduce seismic uncertainty. Wireline formation tester for reservoir pressures and fluid sampling were performed as well as sidewall coring acquisition.

The main results in the reservoirs were; H30-H27: oil bearing (ODT 571.5m MD/RT), H25-TD: water bearing and possible disconnection between H30 and H27; possible difference in OWC for these two levels.

A single injection test was performed in the water leg of the H25 reservoir to better estimate the reservoir properties and heterogeneities

Well Testing

After drilling and logging, well testing started on 3rd November 2012 with the rig OGEC RR600. The primary objectives of the Jobi-5A Injection Test were to assess skin, near-wellbore permeability and transitory (short term) II of the well and to rule on the existence of no-flow boundaries: structural and/or sedimentary limits, lateral facies variations, Water Oil Contact (WOC).

One (1) injection test + Fall-Off test was performed on H25 (Perforation Interval 592-597 m MDRT). The well was then permanently abandoned with cement plugs.

Jobi-6 was planned as an appraisal well within the Central Panel to drill a sub-horizontal drain of 1000 m targeting H25 and H15 reservoir intervals. The well is situated on land within the Murchison Falls National Park in the North Nile Area (~4 km to the North of Victoria Nile and ~6 km to the East of Albert Nile). Jobi-6 was planned to be drilled from the existing Jobi-3 well pad located approximately 3.1 km SSW of Jobi-1, 2,3 km NNE of Rii-1 and 2.7 km South South East of Jobi-5. Jobi-6 wellpath is oriented towards the North North East along the 2D regional seismic line HOG07-12 starting from shot point 1689 (Tullow processed Fast track PSTM dataset, shot point-1689, CMP-1138, trace-1137.

Jobi-6 pre-well objectives were to test the possibility of drilling 1000 m sub-horizontal drain at the shallow depth of 473 mTVD/RT in the Central panel of Jobi-Rii field targeting maximum possible sandy section within H25 (primary target) and H15 (secondary target) reservoirs, to complete a 1000 m long drain with a standalone screens & blanks, to test the wellbore stability during completion, to evaluate the reliability of the development pattern proposed for the Jobi-Rii Field development and to perform one production test within sub-horizontal reservoir section (H25 or H15U) to estimate skin, Kv/Kh, near wellbore Kh & well PI.

Jobi-6 was spudded on 10th October 2013 with the CAROIL-2 rig, and the well reached final total depth (TD) of 1722 m MD/RT) on the 08th November 2013. The well was then tested using stand-alone screens in the drain hole. Well was plugged and abandoned.

Operations and results

Jobi-6 sub-horizontal well intersected all Mio-Pliocene reservoirs from Top H30 down to H15; Top H30 was found at 476.7 m MD/RT. The well reached TD within the H15L at 1722 m MD/RT. The reservoirs are an alternation of unconsolidated sands with soft swelling claystone. An Oil Down To (ODT) was encountered at the toe of the well at -433 m TVDLL in H15U. The well reached TD in the H15L shaley interval. Reservoir properties are very good; however, a slight degradation of the reservoirs along borehole towards North North East (NNE) can be observed. No wireline formation pressure acquired in this well.

Well Testing

Jobi-6 well was tested using the CAROIL-2 rig. The well was tested using stand-alone screens in the drainhole. The well testing objectives for Jobi-6 well were to complete a 1,000m long drain with stand-alone screens, blank pipe, and open hole packers for interval isolation, to test wellbore stability while running the sand screen completion, to assess the reservoir quality of the sandy intervals intersected by the well, to acquire the productivity of a horizontal drain from the H15 interval and perform a production test of the H15 interval to estimate skin, Kh, Kv/Kh and well PI.

The DST was very successful, with excellent reservoir data recovered and maximum targeted production rate of 1,200BOPD achieved. (Actual test data: 1,218BOPD with 253psi (17.4 bar) ΔP drawdown applied using the tubing deployed PCP at a maximum speed of 370RPM).

Mpyo-1 (02N31E/103-2) was the first well to be drilled on the Mpyo (Crocodile) structure by Tullow Oil in Exploration Area 1 of Uganda. It was the second well of the second Exploration Area 1 drilling campaign and was drilled as a vertical exploration well. The well was drilled as a vertical hole, situated on strike line HOG-B1-07-11. The well location is situated 2.0 km south of the Victoria Nile, 6.0km south west of Paraa with the Murchison Falls National Park (MFNP) in the Buliisa County of Buliisa district.

The primary exploration objective of the well was to drill and assess the reservoir potential of the Tertiary sandstones of the Wangkwar Formation with the top predicted to be at 362m tvdbrt. The Mpyo-1 (Crocodile-1) well was drilled by the OGEC RR600 rig.

Mpyo-1 well was spudded on 28th July 2010 and the well was drilled to a final total depth (TD) at 465m MDBRT after penetrating basement with a sufficient logging sump on 9th August 2010.

Operations and results

The reservoir layers, BG1, BG2, BG3, BG4 and BG5 were picked in the Wangkwar formation in Mpyo-1 and are less well developed than was the case in other wells drilled in the Tullow Exploration Area 1.

Interpretation of the wire-line logs run in this section indicates a total of 61.4m of net sand with a Net: Gross of 0.32 and an average porosity of 24%. Significant hydrocarbon saturations were interpreted from logs in layers BG1, BG2 and upper BG3 and the presence of oil as the moveable fluid was confirmed by MDT pressure data and oil samples.

The interpretation indicated separate oil gradients of 0.38 psi/ft and 0.42 psi/ft in layers BG1 and BG3 respectively. The pressure data below the oil leg, in layer BG4, is consistent with a water gradient. The interpreted BG1 oil gradient intersects a water gradient of 0.433 psi/ft, passing through the centre of the BG4 water leg data, at a FWL of +331.9m tvdss while the BG3 oil gradient indicates a FWL at approximately +45.8m tvdss. Oil samples were obtained from layer BG1 and a formation water sample from layer BG4 using the MDT.

Some 7.24m of pay (Pay: Gross 0.16) with an average porosity of 29% and water saturation 53%, was interpreted in layer BG1. This layer consists of thin inter-bedded sands and clays with the result that the logs do not properly resolve the sands and they are underestimated in thickness, porosity and hydrocarbon saturation. The sands were poorly developed in layer BG2 with 2.46m of pay (Pay: Gross 0.1) interpreted with an average porosity of 34% and water saturation of 59%. Layer BG3 had approximately 8.29m of pay (Pay: Gross 0.17) with average porosity 32% and water saturation 51%.

Well Testing

Mpyo-1 intersected several hydrocarbons bearing intervals with good reservoir properties. An extensive logging survey was carried out including formation pressure testing. The following oil bearing zones were intersected at Mpyo-1:

• The H30 sand: 254 - 300 mMDRT (+396.8 to + 350.8 mTVDSS)
• The H25 sand: 325 – 373.5 mMDRT (+325.8 to + 277.3 mTVDSS)

Two tests were performed over H25 and H30 reservoirs. Production tests were carried out on the H30 and H25 reservoir intervals.

H25 main objectives were to assess skin, near-wellbore permeability (permeability of AE6) and transient (short term) PI of the well, to assess the width of the distributaries channel (AE6) that should be intersected by the well, to highlight a potential mobility degradation beyond the channel boundaries, to assess the permeability of the lacustrine mouth bar complex (AE5) expected beyond the channel boundaries and to assess the minimum oil volume connected to the well and the pseudo-steady state (long term) PI of the well.

The Mpyo-2 well is located on land within the Murchison Falls National Park and 3.4 km to the North of Victoria Nile.Mpyo-2 is planned as a vertical well to drill and appraise the up-dip extension of the prospective Mpyo North panel discovered by Mpyo-1 in August 2010. The location is situated on land within the Murchison Falls National Park and 2.4 km to the North of Victoria Nile. Its surface location is approximately 6.7 km North East of Mpyo-1, 5 km East of Jobi-East-5/5a, 3.6 km North-East of Mpyo-4(F) proposed location and 2.4 km West-North West of Til-1. Mpyo-2 is positioned on 2D Regional Seismic line HOG-2010-22 (Tullow’s Fast Track processed dataset, shot point-2720, CMP-3438 and trace-1437).

Mpyo-2 well main targets and well objectives were to drill and appraise the Mpyo North panel up-dip Mpyo-1 discovery, to evaluate quality and continuity of all the reservoir intervals, to prove hydrocarbon presence, quality and productivity, to assess the possible connection or disconnection between the hydrocarbon accumulation in different Mpyo panels, to assess cap rock integrity for very shallow reservoirs (geomechanics) and to assess presence and characterization of “Tarmat”.

Mpyo-2 was planned as a vertical well, the 8 ½” section of which was to act as a ‘pilot hole’ for correlation & selection of coring points in the sidetrack Mpyo-2A well, if hydrocarbon bearing reservoirs were encountered. In a dry hole scenario (all reservoirs identified as water bearing), the sidetrack would not have been drilled (no coring) and the well to be plugged and abandoned following drilling to TD (tagging the H0-basement) and logging (basic wireline logs) of the reservoir and weathered basement sections.

Mpyo-2 well was spudded on 11th June 2013 with the OGEC RR600 rig. The well reached a final total depth (TD) at 309m MD/RT into basement (H0) on 15th June 2013, no oil shows or hydrocarbon fluorescence were encountered while drilling, and no significant formation gas was recorded. A VSP was recorded in the 8 ½” section of Mpyo-2 for seismic calibration of the Mpyo Field. The well borehole was logged for open hole logging acquisitions and subsequently plugged and abandoned.

Operations and results

Mpyo-2 well did not encounter any shows while drilling: cuttings exhibited no hydrocarbon indication and no evidence of formation gas. Mpyo-2 intersected all reservoirs from Top H30 down to the basement (H0). The presence of water in all reservoir zones was confirmed by evaluation of the wireline logs, and analysis of the MDT measurements and samples. Reservoir section was encountered 36 m deeper and thinner compared to prognosis. The reservoir quality is generally fair, although more degraded than Mpyo-1 and 3, and Jobi-East wells.

Mpyo-3 was the third well drilled in 2011 by Tullow Uganda Operations Pty. Ltd. The Mpyo-3 well was designed to appraise the greater up-dip appraisal area of Mpyo-1. Mpyo-3 lies on seismic lines HOG-07-11. Mpyo-3 lies at the northern end of Lake Albert in Exploration Area 1 and the geology of the area is dominated by a fluvio/deltaic depositional environment with rapidly fluctuating lake level changes.

The main objectives of the well were to test for the presence of hydrocarbons within the H15 to H30 sequences, establish OWCs of any hydrocarbon columns encountered, appraise communication with Mpyo-1, and test the lateral extend of the sands, NTG distribution and connectivity with Mpyo-1. The Mpyo-3 well was designed to appraise the greater up-dip appraisal area of Mpyo-1.

Mpyo-3 well was drilled using the same OGEC Cracow IRI-750. The was spudded on 4th May, 2011. The well was drilled vertically to 515m BRT. Intermediate wire line logs were run at this depth. No gas was found in the reservoir, thus the well was then drilled deeper into basement to 584mBRT into the basement, to establish seismic control over Mpyo area. A cement plug was set up to 513m BRT in order to abandon basement section. A 7’’ production casing was run and cemented in place at 509mBRT. A kill string consisting of 148m of 3 1/2” EUE suspension tubing was run and the suspension tree installed. Mpyo-3 operations were completed at 0900hrs on 22nd May, 2011.

Operations and results

General hole condition was good. Some wash out was observed in the H30 where the borehole enlarged to 11”. H30 came in 37m shallower than expected. No gas bearing intervals associated with the well.

H30 encountered 11.28m of pay, with an average porosity of 35.4%. Average Sw was 37%. The H30 net to gross was calculated at 0.8. MREX data indicated high amounts of immovable water (or oil) over the H30, which is common in heavy oil reservoirs. This was further confirmed by failure to obtain an oil sample with the RCI tool.

H25 encountered 39.7m of reservoir quality sands, with an average porosity of 28%. The interval was however entirely water bearing with an average Sw of 97%.

Based on log and pressure data, an OWC was interpreted at 366m (297m TVDSL). RCI pressures and samples were taken. 41 pretests were attempted, with 13 good tests, 4 supercharged, 10 lost seals, 13 tight, and 1 very low permeability test which was not repeated. Samples attempted and recovered at 342m and 426m, both water bearing.

No core was cut in Mpyo-3 only percussion sidewall cores (22 of 25 recovered, 88%).

HDIL, RTEX and 3DEX resistivity were all run on Mpyo-3 to assess and compare the quality of the tool response. There was good correlation between all tools, other than the 3DEX, where Rv appeared higher in the laminated zones as expected.

MREX data acquisition was halted over the H30 interval at 349m due to the proximity of the casing shoe above (335.5m).

Mpyo-4 was planned by Total E&P Uganda as a vertical well (with a sidetrack Mpyo-4A for selective coring) to drill and appraise the Mpyo North Panel in an intermediate position up-dip of the Mpyo-1 discovery well and down dip of the Mpyo-2 dry well. The well is situated on land within the Murchison Falls National Park in the North Nile Area. The surface location is approximately 4.4 km to the North of Mpyo-1, 3.6 km to the South-West of Mpyo-2 and 2.7 km to the South-East of Jobi East 5. Mpyo-4 was positioned on 2D regional Seismic line HOG07-09 (Fugro processed PTSM 2D Regional Seismic Data, Shot point-748, CMP-2314 and Trace-314

Mpyo-4 was planned to intersect all the Mio-Pliocene reservoirs down to the weathered basement (H1). The well objectives were to drill and appraise the Mpyo North panel up-dip Mpyo-1 discovery and down dip of Mpyo-2, to evaluate the quality and the continuity of the reservoirs, to prove hydrocarbon presence, quality and productivity, to assess the possible connection or disconnection between the hydrocarbon columns in different Mpyo panels, to assess cap rock integrity for very shallow reservoirs (geomechanics) and to assess reservoir injectivity and fracking regime (geomechanics).

Mpyo-4 was spudded on 26th June 2013 with the OGEC RR600 rig. The pilot-hole reached TD at 428 m in H1 weathered basement on 1st July 2013.

Operations and results

Mpyo-4 intersected the Mio-Pliocene reservoirs from H30 down to H1 weathered basement. Top H30 was encountered at 257.6 m MD/RT (-222.0 m TVDLL) in the pilot hole (31 meters deeper than prognosis). The mismatch between actual tops and prognosis varies from +30 meters to -1.7 meter at the other key reservoir tops.

Reservoirs have fair to good petrophysical properties. The best porosity is in H27 (Average of 27 %) while H30 has the largest porous height (net height*porosity): 4.38 meters.

H30, H27 and H25 were encountered oil-bearing. The H25 reservoirs appears with an ODT at 328 m MD/RT (- 292 m TVDLL). Reservoirs H15 and below are water-bearing.

MDT pre-tests are scattered and do not allow interpreting FWL in any reservoirs. If possible, the connectivity of Mpyo-4A with other Mpyo wells is difficult to evaluate.

Sands named H35 and H33 overlying the regional seal at top H30 presented some oil shows while drilling, on resistivity logs and during the sampling. However, production test concurs to demonstrate that water is the mobile phase in these reservoirs. Oil shows are interpreted as marks of migration pathway.

Mpyo-4A was planned by Total E&P Uganda as a sidetrack Mpyo-4A for selective coring to drill and appraise the Mpyo North Panel in an intermediate position up-dip of the Mpyo-1 discovery well and down dip of the Mpyo-2 dry well. The well is situated on land within the Murchison Falls National Park in the North Nile Area. The surface location is approximately 4.4 km to the North of Mpyo-1, 3.6 km to the South-West of Mpyo-2 and 2.7 km to the South-East of Jobi East 5. Mpyo-4 was positioned on 2D regional Seismic line HOG07-09 (Fugro processed PTSM 2D Regional Seismic Data, Shot point-748, CMP-2314 and Trace-314

Mpyo-4A was planned to intersect all the Mio-Pliocene reservoirs down to the weathered basement (H1). The well objectives were to drill and appraise the Mpyo North panel up-dip Mpyo-1 discovery and down dip of Mpyo-2, to evaluate the quality and the continuity of the reservoirs, to prove hydrocarbon presence, quality and productivity, to assess the possible connection or disconnection between the hydrocarbon columns in different Mpyo panels, to assess cap rock integrity for very shallow reservoirs (geomechanics) and to assess reservoir injectivity and fracking regime (geomechanics).

Having encountered hydrocarbons in Mpyo-4, the pilot hole was plugged back after basic logging. Sidetrack Mpyo-4A was initiated at 180 m on 4th July 2013 and reached final total depth (TD) at 419 m on 14th July 2013.

Dean & Stark centre core samples were taken at the base or top of each 1m cut core section where possible throughout the coring. A total of 27 Dean & Stark cores were taken during the coring.

Operations and results

Mpyo-4 intersected the Mio-Pliocene reservoirs from H30 down to H1 weathered basement. Top H30 was encountered at 257.6 m MD/RT (-222.0 m TVDLL) in the pilot hole (31 meters deeper than prognosis). The mismatch between actual tops and prognosis varies from +30 meters to -1.7 meter at the other key reservoir tops.

Reservoirs have fair to good petrophysical properties. The best porosity is in H27 (Average of 27 %) while H30 has the largest porous height (net height*porosity): 4.38 meters. H30, H27 and H25 were encountered oil-bearing. The H25 reservoirs appears with an ODT at 328 m MD/RT (- 292 m TVDLL). Reservoirs H15 and below are water-bearing.

MDT pre-tests are scattered and do not allow interpreting FWL in any reservoirs. If possible, the connectivity of Mpyo-4A with other Mpyo wells is difficult to evaluate.

Sands named H35 and H33 overlying the regional seal at top H30 presented some oil shows while drilling, on resistivity logs and during the sampling. However, production test concurs to demonstrate that water is the mobile phase in these reservoirs. Oil shows are interpreted as marks of migration pathway.

Well Testing

Tests were carried out later with the ZPEB-26 (workover unit) rig. Following testing operations, Mpyo-4A well was plugged and abandoned.

DST #1 (production test with PCP) in H25 was highly affected by sand production and oil sampling could not be performed for that reason. On the contrary mini-frac and viscosified water injection tests were carried out successfully.

DST#2 (production test) in H30 was carried out using a sand screen included in the DST string. Therefore, the issue of sand production was solved. The well was flowed at very low rate using PCP. Mini-frac and viscosified water injection tests were also carried out successfully in this reservoir.

DST #3 in H35 produced only water.

Mpyo-5 was planned as a vertical well by Total E& P Uganda with a sidetrack for selective coring. The well is located on land within the Murchison Falls National Park and about 1.7 km South of the Victoria Nile. The purpose of the well was to appraise the up-dip extension of the prospective Mpyo South Panel to the North-East of Mpyo-3 discovery (located 2.5 km South-West).

The main targets and well objectives were to drill and appraise up-dip extension of Mpyo South panel to the North-East of Mpyo-3 discovery, to drill and appraise the H30 proven reservoirs in the Mpyo-3 panel, to evaluate the presence of hydrocarbon in the H27 and H25 reservoirs up-dip of Mpyo-3, to evaluate the quality and continuity of all reservoir zones, to evaluate productivity and injectivity of the key reservoir intervals, to assess the cap rock integrity for very shallow reservoirs (geomechanics), to assess reservoir injectivity and fracture regime (geomechanics).

Mpyo-5 well was spudded on 31st July 2013 with the OGEC IRI 750 rig. The well reached a final total depth (TD) at 392 m MD/RT on 6th August 2013.

Operations and results

Mpyo-5 was drilled as a vertical appraisal well with a planned sidetrack for selective coring. The well intersected the Mio-Pliocene reservoirs from H30 down to H1 weathered basement. Top H30 was encountered at 257.2 m MD/RT (-223.9 m TVDLL) in the pilot hole, that is 29.9 meters deeper than expected from well prognosis.

Only H30 reservoir interval encountered oil-bearing. Oil shows were evidenced while drilling, on wireline logging and visible on cores. No clear OWC was encountered in the well, MDT pretests are scattered and does not allow interpreting FWL in the reservoir. Reservoirs H27 and below are water-bearing. Reservoirs have fair to high petrophysical properties. The best porosity was encountered in reservoir H30 (25%).

No production test was possible due to limited oil bearing interval.

Mpyo-5A was planned as a sidetrack well for Mpyo-5 by Total E& P Uganda for selective coring. The well is located on land within the Murchison Falls National Park and about 1.7 km South of the Victoria Nile. The purpose of the well was to appraise the up-dip extension of the prospective Mpyo South Panel to the North-East of Mpyo-3 discovery (located 2.5 km South-West).

The main targets and well objectives were to drill and appraise up-dip extension of Mpyo South panel to the North-East of Mpyo-3 discovery, to drill and appraise the H30 proven reservoirs in the Mpyo-3 panel, to evaluate the presence of hydrocarbon in the H27 and H25 reservoirs up-dip of Mpyo-3, to evaluate the quality and continuity of all reservoir zones, to evaluate productivity and injectivity of the key reservoir intervals, to assess the cap rock integrity for very shallow reservoirs (geomechanics), to assess reservoir injectivity and fracture regime (geomechanics).

On drilling Mpyo-5, oil shows and formation gas shows were encountered while drilling, and following TD logging the well was plugged back to drill a sidetrack section (Mpyo-5A) in order to perform coring operation. Following coring and comprehensive wireline logging the 7” casing was run and set, and the well temporarily plugged and abandoned for a future well-test to be carried out. The rig was released on 20th August 2013.

Operations and results

Mpyo-5A was drilled as a sidetrack well for selective coring. Eight (8) continuous cores were cut from 250 m MD/RT to 281 m MD/RT with 30.2 m (97%) of core recovery.

Mpyo-5A intersected the Mio-Pliocene reservoirs from H30 down to H1 weathered basement. Top H30 was encountered at 257.2 m MD/RT (-223.9 m TVDLL) in the pilot hole, that is 29.9 meters deeper than expected from well prognosis.

Only H30 reservoir interval encountered oil-bearing. Oil shows were evidenced while drilling, on wireline logging and visible on cores. No clear OWC was encountered in the well, MDT pretests are scattered and does not allow interpreting FWL in the reservoir.

Reservoirs H27 and below are water-bearing. The reservoirs have fair to high petrophysical properties. The best porosity was encountered in reservoir H30 (25%).

No production test was possible due to limited oil bearing interval. An injectivity test was initially planned in H30 reservoir to evaluate dynamic properties. Mpyo-7 well, drilled later, showed same poor hydrocarbon(HC) result and this limited the interest of the area. The injectivity test on Mpyo-5A was then cancelled.

Mpyo-6 well was planned as a vertical well drilled to appraise the down-dip extension of Mpyo South Panel South West of Mpyo-1 discovery. Mpyo-6 is located on land outside the Murchison Falls National Park, about ~6 km to the North of Bugungu Camp and 1.3 km to the South of Victoria Nile. Surface location is approximately 2.8 km to the South-West of Mpyo-1 and 3.9 km South-West of Mpyo-3. Mpyo-6 is positioned on 2D Regional Seismic line HOG07-13 EXT (Fugro processed PSTM 2D Regional Seismic data, shot point-1442, CMP-486 and Trace-485).

The main pre-well objectives were to drill and appraise the down-dip extension of Mpyo South Panel to the South-West of Mpyo-1 discovery, to evaluate the quality and continuity of all reservoir zones, to test the oil productivity close to the Water Oil Cotact (WOC) within H30 reservoir interval in success case, to perform an injectivity test with in H25 water leg in dry or success case and to assess the cap rock integrity for deeper reservoirs (geomechanics).

Mpyo-6 was spudded on 20th September 2013 with OGEC K900 rig and the well reached final total depth (TD) on 1st October 2013 at 628 m MD/RT (-584.1 m TVD/LL), that is 18 meters below the top H1 Weathered Basement. No coring operation was performed and the well was suspended subsequent to the wireline logging operation.

Mpyo-6 is planned to be tested in December 2013.

Operations and results

Mpyo-6 intersected all Mio-Pliocene reservoirs from Top H30 down to weathered basement (H1). Top H30 was encountered at 411.1 m MD/RT (-367.2 m TVD/LL), 4 m shallower than prognosed.

Reservoirs facies represented by an alternation of unconsolidated sands with soft swelling clays and have fair to good petrophysical properties. Over all net sand thickness within reservoir intervals (H30 to H01) is 78.45 m with an average NTG of 40%.

H30 sands are relatively well developed in comparison to its up-dip counterpart Mpyo-1. Only minor oil shows were observed at the base of the H30U and in the H30L with a little gas pocket of <2 m at 432 m TVD/RT.

H27U was HC bearing with ODT identified at 465.5 m MD/RT (-421.6 m TVD/LL) with reservoir facies very well developed with an NTG of 43%, average PhiE of 31% and Shc of 70%. Lower part of H27U and H27L is highly argillaceous and represent a bottom seal for the H27U oil accumulation.

The section from top H25 down to weathered basement H1 was relatively sandy with interbedded clays and lacks any HC show.

Pseudo-potential plot of Mpyo-6 pressure data and sampling confirms small gas pocket within the lower part of H30 with H30 aquifer isolated from deeper Mpyo reservoirs.

Hydrocarbon accumulation within H27 level in Mpyo-6 is not in communication with Mpyo-1 and a separated OWC from pretests interpretation is seen deeper than ~-500 m TVD/LL. Pressure measurements from H25 and H15 levels confirm water bearing reservoirs. A production test and an injection test within H27U oil reservoir are planned in December 2013.

Well Testing

Production test # 1 was carried out on the H27U reservoir interval. The well was perforated from 454 to 465.5m MD/RT. The oil bearing zones were tested in H27 sand: 454 – 465.5mMD/RT. The objectives for well testing were to characterize the productive potential (Skin, K*h, Kv/Kh, IP), to recover surface and bottom hole fluid samples for P VT and flow assurance studies, to determine heterogeneities and limits if possible and to evaluate the connected volume to the well.

Progressive cavity pump was used during the whole test and the efficiency was good. The average production rate during the main flow was 195bpd (31m3/d). The BSW was 0% and the density of around 22 degrees API.

Dead oil was sampled at the tank with 5 can of 20 litres.

Injection test was successfully performed; the quality of data is good and will be used for further interpretation. Sensitivity to flow rates during injection test was to be performed to confirm the higher mobility.

Ngiri-2 (Warthog-2) was the second well to be drilled on the Ngiri (Warthog) structure by Tullow Oil in Exploration Area 1 of Uganda. It was the first well of the second Exploration Area 1 drilling campaign and was drilled as a vertical appraisal well. The principal offset well is Ngiri-1 (Warthog-1) discovery well. Other offset wells were the Heritage Oil discovery wells Rii-1 and Jobi-1 to the north east in Exploration Area 1. Further offset information was provided by wells to the south within Exploration Area 2, primarily the Kasamene-1, Ngege-1, Taitai-1 and Karuka-1 wells, drilled by Tullow Uganda Ltd within the Butiaba region. The well was drilled as a vertical hole, located on seismic line HOG-B1-07-19.

The primary exploration objective was to drill and assess the reservoir potential of the Tertiary sandstones of the Wangkwar Formation, with the top predicted to be at 664m tvdbrt.

The well was spudded at on 27th June 2010 with OGEC RR600 rig and reached a final total depth (TD) of 892 m MDBRT on 12th July 2010 after encountering basement prematurely. The well was then suspended with the casing and a blind flange installed and tested. Inhibited KCl-polymer mud at 1.21sg (10.1ppg) was left in the well bore.

Operations and results

Petrophysical Analysis interpretation indicated the presence of an oil bearing interval from 625.5m to 755.6m tvdbrt (FWL), a gross interval of 130.1m of which 42.3m is pay. Layer BG1 has a gross thickness of 55.5m, 13.2m of which are pay with an average interpreted porosity of 24%.

Layer BG2 has a gross thickness of 72.5m with 29.1m of pay and an average porosity in the pay sands of 29%, with average water saturation of 35%.

Layer BG3 has a gross thickness of 48.5m with 30.6m of net and an average porosity of 29% in the net sand. No pay occurs in this layer.

The MDT formation pressure data confirmed that separate oil gradients occur in layers BG1 and BG2 separated by some 22 psi. A water gradient was indicated in layer BG3. The intersection of the BG2 oil gradient and BG3 water gradient indicated a FWL at 106.6m tvdss (755.6 tvdbrt). The intersection of the BG1 oil gradient with the water gradient results in a FWL of 246.7m tvdss (deeper than TD).

Well Testing

In November 2011, wellhead pressure surveys by the interim operator Tullow-Uganda indicated positive wellhead pressure of up to 14.3 bar (210 psi). A subsequent pressure bleed-off and monitoring operation offered successful indices for a cautious well re-entry; pressure stabilized at 0 psi for about 2 hrs and only 24 psi after 5 days.

On 24th March 2012, the OGEC IRI750 rig was mobilized onto location by Total E&P Uganda for well testing operations by Schlumberger as principal service company.

The well test objectives were to determine S and KH around wellbore and short term productivity (transient PI), to rule on the sealing properties of the fault separating central panel from north panel, to estimate the distance from well to WOC, to estimate the oil volume connected to the well and long term productivity (pseudo-steady state PI), to collect dead crude oil samples at the separator for crude analysis and to determine contribution of the two individual sand packages through PLT operations.

Remedial cement jobs to isolate the H15 and lower reservoirs from the H27 isolate the H27 and the H30 as well as isolate the H30m from the surface were performed. Three perforating runs and balanced cement plugs were squeezed to achieve these isolations; isolation of the H15 and lower formations (750-746m and 716-708m), isolation of the H27 from the H30 (665m-653m and 631m-628m) and isolation of the H30 from surface (574m-570m). In order to test the H27, these cement plugs were drilled-out to 705m.

The well was opened on an adjustable 8/64 choke, it was an eruptive with initial flow of 34 - 50 m3/day. During the clean-up, the well was inadvertently shut-in whilst attempting to bleed-down the annulus pressure; the annulus was bled down completely thus causing the safety valve to shut. It was subsequently re-opened and beaned-up to184 m3/day and continued to flow at a stable rate of 222 m3/day.

Due to the nature of the crude produced (wax and asphaltene content), the test string above the IRDV was flushed and in this process, the LINC tool disconnected and was pumped up the hole. (The tool string was not latched). The LINC was retrieved and a new cable head built, it was subsequently re-connected.

The initial shut in period lasted 38 hours, after this time the well was opened on the main flow period of 60 hours. The LINC tool indicated high data noise in the late time-data potentially attributable to the tubing circulation during the initial build-up. An additional 100 hrs build up was performed. The LINC tool however failed on this run and it was therefore not possible to evaluate the build-up performance in real time.

After the build-up period, the well was killed, DST string retrieved and plugged and abandoned with cement; two set of perforations were made at 353-357m and 340-344m, cement plugs set and squeezed. A surface cement plug was set and the casing cut at the bottom of the cellar. All surface wellhead was recovered and the rig released on 6th May 2012.

Mpyo-7 was a vertical well to drill and appraise the up-dip South- East lateral extension of Mpyo-South Panel to the South-East of Mpyo-3 well. Mpyo-7 is located on land within the Murchison Falls National Park, about ~5 km to the South of Victoria Nile and 7.4 km to the North-East of Bugungu Camp. Surface location is approximately 2.4 km South-East of Mpyo-3 and 4.2 km to the South-East of Mpyo-1. Mpyo-7 is positioned on 2D Regional Seismic line HOG07-11 (Fugro processed Final PSTM 2D Regional Seismic data, shot point-380, CMP-983 and Trace-982).

The main targets and well objectives were to drill and appraise the up-dip lateral extension of Mpyo South Panel to the South-East of Mpyo-3 well, to appraise H30 proven interval and to prove the hydrocarbon presence in the H27 and H25 reservoirs at an up-dip location of Mpyo-3, to evaluate the quality and continuity of all reservoir zones.

Mpyo-7 was spudded on 14th October 2013 with OGEC IRI 750 rig and the well reached final total depth (TD) on 20th October 2013 at 530 m MD/RT (-428.5 m TVD/LL), that is 5 meters below the top H1 Weathered Basement. Neither coring nor testing operations were planned in Mpyo-7. The well was plugged and abandoned subsequent to the wireline logging operation.

Operations and results

Mpyo-7 intersected all Mio-Pliocene reservoirs from Top H30 down to weathered basement (H1). Top H30 was encountered at 346.7 m MD/RT (-245.2 m TVD/LL).

Reservoirs facies were represented by an alternation of unconsolidated sands with thin clays and have fair to good petrophysical properties. All the reservoir intervals (H35 to H01) show very well-developed sands with overall net sand thickness of 178 m with an average NTG of 65%.

Minor hydrocarbon shows while drilling was encountered within H35 sands underneath the first regional seal (H40 clays).

All the other conventional reservoirs (H30 to H25 are devoid any hydrocarbon shows or gas indications while drilling).

Quantitative petrophysics interpretation indicated two small hydrocarbon bearing intervals within H35 section with saturation ~30% and average effective porosity of ~22%.

Pseudo-potential plot of Mpyo-7 pre-tests indicated that the pressure points within H35 to H30 are aligned along the regional intermediate aquifer trend within Mpyo field. Even though the pressure measurements within H35 level do not clearly confirm hydrocarbon presence, LFA analysis during fluid sampling indicated minor oil shows. Pressure measurements and sampling from H27 down to H15 clearly indicate water bearing reservoirs.

02N31E/114-3 (Ngiri-3) was planned as a vertical well to drill and appraise the down-dip extension of the Central West and North Panels of the Ngiri field. Ngiri-3 well is situated on the 3D seismic line 1842 and Xline 1777 west of offset wells Ngiri-1 and Ngiri-2.

The main purpose of the well is to appraise the down dip extension of oil bearing reservoirs in the Ngiri Central West and North panels. The objectives of the well were to appraise the extension of oil down-dip of Ngiri-2 in the H30 reservoir interval, to acquire data to confirm fluid contacts within the H30 and H27-H15, which are interpreted to be stratigraphically disconnected and finally to assess quality of all reservoir intervals (H30 expected oil bearing, H27 expected oil and water bearing and H25 and H15 expected water-bearing at proposed well location).

02N31E/114-3 (Ngiri-3) well was spudded on 31st May 2012 with OGEC IRI 750 rig and drilled to 1017 m MD/RT a final total depth(TD) on 15th July 2012.

Operations and results

02N31E/114-3 (Ngiri-3) vertical well intersected all Miocene to Pliocene reservoirs from Top H30 down to virgin basement (H0). Top H30 was found at 695 m MD/RT (-666 m TVD/LL). The well TD was reached 30 metres below top H0 at 1017 m MD/RT (-988 m TVD/LL). The reservoirs are an alternation of unconsolidated sands with soft swelling claystones.

Confirmation of the presence of hydrocarbons. The H30 and H27-15 reservoirs are disconnected. H30 extrapolated WOC appears at -780 m TVD/LL (WFT extrapolation) and H27-H15 OWC at -738 m TVD/LL.

H30 reservoir was oil bearing, H27 is oil and water bearing (OWC @ -738 m TVD/LL) and H25 to H0 are water bearing. Very good reservoir properties with more than 30% of average porosity. The well tests showed good permeability around 5000 mD. Following the drilling of the well, a production and an injection tests were performed in H30.

Well Testing

Ngiri-3 was drilled as a vertical well that has been drilled to appraise the down-dip extension of the Ngiri Northern (Ngiri-2) and Central West panel of the Ngiri Field structure. The well was tested by Schlumberger as the principal service company on behalf of Total E&P Uganda.

The main objectives of the well test were to assess skin, near-well bore permeability (permeability of AE6) and transitory (SHORT TERM) PI of the Well, to highlight potential mobility degradation beyond the channel boundaries, to assess the width of the distributary channel (AE6) that should be intersected by the Well, to assess the permeability of the lacustrine mouth bar complex expected beyond the channel boundaries and to assess the minimum oil volume connected to the well and the pseudo-steady state (long term) PI of the well.

The objectives of Water Injection test were to assess an injectivity rate, to identify the swelling effects of H30, to plot BHFP vs. Qinj curve in matrix regime, to assess if pseudo-fracturing of the sands cam be triggered prior to fracturing the cap rock and to plot BHFP vs. Qinj in pseudo-frac regime.

Ngiri-3 was successfully perforated and tested as per program, good data was recovered. The injectivity test was carried out with success and good data recovered.

The well was permanently plugged and abandoned with cement plugs at the end of well testing operations.

02N31E-114-4 (Ngiri-4) was planned as a vertical well drilled by Total E&P Uganda with a sidetrack. The well is located on land in the Buliisa area, south of the Victoria Nile, outside the Murchison Falls National Park. The well was drilled in the Ngiri Central East panel of the Ngiri field structure in Ugandan Exploration Area 1 (EA1). Ngiri-4 well is located about 2 km North East of Ngiri-1 and 0.8 km from Ngiri-2 to the North-East on Inline 1834 Fast track and Xline 2059 Fast track seismic line.

The pre-well objectives were to drill and appraise the up-dip extension of the Ngiri Central East panel, to calibrate amplitude on H30 (gas or reservoir quality response), to investigate base case assumption that the Central East panel is connected to the North panel, to define a WOC in the H17 interval, between H25 and H15, to evaluate all reservoirs quality and connectivity, to drill to the top H1 until recognition of the Ironstone level (no logging sump), to perform 1 production test in H25 and to perform 2 injectivity test in H25 and H27U oil leg.

Ngiri-4 well was spudded on the 3rd November 2012 with the OGEC IRI750 rig, and the pilot hole reached final total depth of 791.2 m MDRT (-764.0 m TVDLL) within the H15 reservoir on 13th November 2012. Data acquired from Ngiri-4 pilot hole was later used to select & correlate coring points in the sidetrack well.

Operations and results

02N31E-114-4 (Ngiri-4) vertical pilot well intersected the reservoirs from Top H30 down to the H15.

H30 and H27 are oil & gas bearing and are disconnected. Two clear gas effects are seen at top of H30 and at the top of H27.

H25 was oil-bearing down to ODT at 754m (726.1 m TVDLL). No OWC seen. This confirmed the fluid and contacts of H25-H27 observed in previous Ngiri wells.

H17 to H1 are water bearing.

Very good reservoir properties with 28% of average porosity.

Pressure gradients from wire-line tester prove a good connectivity with the surrounding wells and a consistency in the fluid contacts.

02N31E-114-4A (Ngiri-4A) was planned as a sidetrack well for selective coring drilled by Total E&P Uganda. The well is located on land in the Buliisa area, south of the Victoria Nile, outside the Murchison Falls National Park. The well was drilled in the Ngiri Central East panel of the Ngiri field structure in Ugandan Exploration Area 1 (EA1). Ngiri-4A well is located about 2 km North East of Ngiri-1 and 0.8 km from Ngiri-2 to the North-East on Inline 1834 Fast track and Xline 2059 Fast track seismic line.

The pre-well objectives were to drill and appraise the up-dip extension of the Ngiri Central East panel, to calibrate amplitude on H30 (gas or reservoir quality response), to investigate base case assumption that the Central East panel is connected to the North panel, to define a WOC in the H17 interval, between H25 and H15, to evaluate all reservoirs quality and connectivity, to drill to the top H1 until recognition of the Ironstone level (no logging sump), to perform 1 production test in H25 and to perform 2 injectivity test in H25 and H27U oil leg.

02N31E-114-4A (Ngiri-4A) sidetrack was initiated on the 17th November 2012 kicking off at 575 m MD/RT and following the coring operations, final total depth (TD) was reached on the 2nd December 2012 at 881.5 m MD/RT. The Ngiri-4A sidetrack cut all reservoirs from the H30 to the weathered basement zone (H1). The Nigri-4A TD was inside the weathered basement.

Operations and results

02N31E-114-4A (Ngiri-4A) was drilled as a sidetrack to enable selective coring of the reservoir units. The Nigri-4A TD was inside the weathered basement, H1 at 881.5 m MDRT (-853.1 m TVDLL). Top H30 was found at 619.2 m MD/RT in both Ngiri-4 and 4A, (-591.8 / -591.7 m TVD/LL respectively) very close to prognosis (-592 m TVDLL). The reservoirs consist of poorly consolidated sand/sandstones between soft swelling clays / claystones.

A total number of 10 cores were cut in Ngiri-4A. The first core cut in the top seal above the H30, followed by the ands in the H30, Upper H27 & H25 reservoirs. This selective targeting led to an average core recovery of 90%.

In addition to the conventional logs necessary for formation evaluation, spectroscopy and magnetic resonance were run to address uncertainty on reservoir properties.

A VSP was recorded in the 8 ½” section of Ngiri-4A for accurate seismic calibration of the Ngiri Field.

Extended pressure tests were made after each sample was taken. Following drilling, a production test and an injection test were carried out in the H25, and an injection test in the H27.

H30 and H27 are oil & gas bearing and are disconnected. Two clear gas effects are seen at top of H30 and at the top of H27.

H25 was oil-bearing down to ODT at 754m (726.1 m TVDLL). No OWC seen. This confirmed the fluid and contacts of H25-H27 observed in previous Ngiri wells.

H17 to H1 are water bearing.

Very good reservoir properties with 28% of average porosity.

Pressure gradients from wire-line tester prove a good connectivity with the surrounding wells and a consistency in the fluid contacts.

Well Testing

Following drilling, a production test and an injection test were carried out in the H25, and an injection test in the H27. Well test in H25 (flow test followed by a water injection test) ascertained dynamic parameters of these reservoirs. The H25 reservoir flowed naturally at an average rate of 1200 stb/day in the main flow period. Interpretation of results from the production test indicated a high-quality reservoir of 8000 mD. Water injection tests were also carried out on the same interval using both viscosified and fresh water. Only matrix flow regime was achievable.

Water injection tests were also carried in the oil pool of H27 reservoir using both viscosified and fresh water. For this test also, only matrix flow regime was identified

Ngiri-5 is located on land in the Buliisa area, south of the Victoria Nile, outside the Murchison Falls National Park. Ngiri-5 well was drilled in the Ngiri South panel of the Ngiri field structure in Uganda Exploration Area 1 (EA1). Ngiri-5 was planned as a vertical well located on Xline 1740 Fast Track and Inline 1785 Fast Track. The purpose of the well was to appraise the up-dip extension of the Central East Panel of the Ngiri Field. The other objectives were to prove oil in the H30 in the Ngiri South Panel, to confirm the base case assumption that the H30 interval is disconnected from other intervals below, to recognize and evaluate all reservoirs down to H1 (weathered basement) and to perform production test in the sidetrack, according to well results.

Ngiri-5 well was spudded on 14th February 2013 with OGEC IRI750 rig, and the pilot hole reached a final total depth (TD) of 760 m MDRT on 26th February 2013. The pilot hole was used for correlation and selection of coring points in the sidetrack.

Operations and results

The Ngiri-5 vertical pilot well intersected the Upper Miocene to Pliocene reservoirs from the Top H30 down to the H27. The well final (TD) at 760 m MD/RT (-724.1 m TVDLL) within the H27 reservoir.

H30 is oil-bearing and H27 is oil & water-bearing. H30 was oil-bearing down to ODT at 728.5 m MD/RT (-692.5 m TVDLL). No OWC observed in H30.

H27 was oil- bearing down to ODT at 752 m MD/RT (-716 m TVDLL). OWC not encountered in the well (WUT at 774 m MD/RT (-737.9 m TVDLL). This is concordant with the fluid and contacts seen on previous Ngiri wells.

H25, H17, H15 and H14 were water-bearing. The reservoir properties were as expected and very similar with those of neighbouring wells. The average effective porosity (after cut-off) is 22% in H30 and 27% in H27.

Ngiri-5A was drilled as a sidetrack for selective coring. The well is located on land in the Buliisa area, south of the Victoria Nile, outside the Murchison Falls National Park. Ngiri-5 well was drilled in the Ngiri South panel of the Ngiri field structure in Uganda Exploration Area 1 (EA1). Ngiri-5A was planned as a sidetrack well located on Xline 1740 Fast Track and Inline 1785 Fast Track. The purpose of the well was to appraise the up-dip extension of the Central East Panel of the Ngiri Field. The other objectives were to prove oil in the H30 in the Ngiri South Panel, to confirm the base case assumption that the H30 interval is disconnected from other intervals below, to recognize and evaluate all reservoirs down to H1 (weathered basement) and to perform production test, according to well results.

Ngiri-5A sidetrack was initiated from 591 m MDRT on 28th February 2013, kicking off at 665 m MDRT and following the coring operations final total depth (TD) of 953 m MDRT was reached on 10th March 2013.

A number of 6 cores were selectively cut within the H30 reservoir. This selective targeting led to an average core recovery of 96%. In addition to the conventional logs necessary for formation evaluation, spectroscopy and magnetic resonance were run to address uncertainty on reservoir properties.

A VSP was recorded in the 8 ½” section of Ngiri-5A for seismic calibration of the Ngiri Field. Extended pressure tests were made after each sample was taken. Following drilling and logging, a production test was carried out in the H30.

Operations and results

Ngiri-5A was drilled as a sidetrack for selective coring. A total of 6 cores were selectively cut within the H30 reservoir achieving a 96% recovery success.

H30 was oil-bearing and H27 was oil & water-bearing. H30 was oil-bearing down to ODT at 728.5 m MD/RT (-692.5 m TVDLL). No OWC observed in H30.

H27 was oil- bearing down to ODT at 752 m MD/RT (-716 m TVDLL). OWC not encountered in the well (WUT at 774 m MD/RT (-737.9 m TVDLL). This is concordant with the fluid and contacts seen on previous Ngiri wells.

H25, H17, H15 and H14 are water-bearing. The reservoir properties are as expected and very similar with those of neighbouring wells. The average effective porosity (after cut-off) is 22% in H30 and 27% in H27.

The pressure gradients from wire-line tester proved a good connectivity with the surrounding wells. H30 is disconnected from others reservoirs below.

Well Testing

Following drilling and logging, a production test was carried out in the H30. The well was tested between the 29th March and 3rd April 2013. Only H30 level was produced and tested.

The objectives of the well test were to determine permeability and skin of the well. Assess the short term (transient) productivity, to assess the sealing capacity of main faults, to determine the existence of any near reservoir heterogeneities and limits, to estimate the oil connected volume to the well and to carry out oil surface sampling.

Well test in H30: well flowed naturally throughout the test at an average rate of 377 STB/day in the main flow period. Interpretation of the data indicated a high-quality reservoir with permeability in the range of 1 to 2 Darcies. Flow barriers in the vicinity of the well were also detected by this well test. All well test objectives were achieved.

02N31E-114-6 (Ngiri-6) is located on land in the Buliisa area, south of the Victoria Nile, outside the Murchison Falls National Park. The well was planned as a deviated well to appraise the Northern panel of the Ngiri structure positioned on the 3D seismic grid (Inline: 1857 Xline: 2183 - Tullow processed PSTM dataset).

The main objectives of the well were to drill and appraise the Ngiri Northern Panel, to confirm the direct hydrocarbon identifications, to confirm the suggested H30-H27 fluid disconnection, to recognize and evaluate all reservoirs down to H1 (weathered basement) and to evaluate all reservoirs quality and connectivity.

Ngiri-6 was spudded on 3rd May 2013 with OGEC K900 rig and the well reached final total depth (TD) at 1203 m MDRT on 20th May 2013. There was no well test planned in this well. The well was plugged and abandoned after logging operations. Logging included conventional logs (SGR-SP-Neutron-Density-Resistivity), wire-line pretests and sampling (MDT), magnetic resonance & resistivity imaging tools. A walk-above VSP was also recorded.

Operations and results

Ngiri-6 was drilled as a directional well with objective to drill the 16” hole section vertically, kick off in the 12 ¼” section just below the 13 3/8” shoe, then build inclination to 52.65º at a BUR of 4.75º/30m in a 4.68º azimuth and hold tangent section to 9 5/8” casing point at 737m MDRT. The 8 ½” section would remain tangent to well TD at 1263m after crossing all reservoir targets.

The well intersected all Mio-Pliocene reservoirs from the Top H30 down to H14 and TDed in weathered basement H1. The top of the main target H30 was encountered at 813.0 m MDRT (-612.1 m TVDLL). The reservoir units are characterized by poorly consolidated sand and occasional cemented sandstones with intercalated clays. The well was drilled to a total depth of 1203 m MDRT (-873.9 m TVD/LL) with top H1 weathered basement at 1180.6 m MDRT (860.6 m TVD/LL).

The main results of the well were all the prognosed reservoirs were encountered from H30 down to the H1 Weathered basement with little difference in depth between prognosis and actual results.

H30 was oil bearing, however the H30L (top at 859.1 m MD/RT / -643.3 m TVDLL) was suspected to be water bearing.

H27 was oil bearing and H25 was oil bearing to ODT at 956 m MD/RT (-711.1 m TVDLL), and water-bearing from WUT at 961 m MD/RT (-714.6 m TVDLL). The OWC was indeed slightly deeper than the prognosed at 700 m TVDLL.

Interpretation on pressure measurements confirms the suggested disconnection between H30 and H27. H25 pressure are also slightly shifted compared to H27 data, meaning that H27 and H25 are not in communication, though the difference in pressure regime was much less than the one observed between H30 and H27.

The total reservoir quality was very good with a total Net of 107 m TVD and average PhiE 26%. The well has proven the hydrocarbon presence in the Ngiri Northern Terrace.

02N31E-114-7 (Ngiri-7) well is located on land in the Buliisa area, south of the Victoria Nile, outside the Murchison Falls National Park, and outside the Ramsar area. The well is positioned using the 3D Buliisa seismic data (Inline 1817 Fast track and Xline 1949 Fast Track); its surface location situated approximately 0.95 km South of Ngiri-2 and 0.7 km North of Ngiri-1.

The well was planned to intersect the Upper Pliocene Reservoirs in the Central-Central Panel with the objectives to drill and appraise the Ngiri Central-Central panel, to assess the reservoir characteristics of the Ngiri Central-Central Panel, especially for the H30 reservoir interval, to assess the Oil-Water Contact (OWC) and possible disassociations between the H30 and H27 reservoir intervals and to evaluate fluid contacts and pressure regime of the H30 to H15 reservoir intervals.

Ngiri-7 well was spudded on 21st May 2013 with OGEC IRI750 rig, and the well reached a final total depth (TD) of 918.3 m MDRT on 1st June, 2013. Subsequent to wireline acquisition in the 8 3/8” section the borehole was permanently plugged and abandoned with the rig released on 19th June 2013.

Operations and results

Ngiri-7 vertical well intersected the Upper Miocene to Pliocene reservoirs from the Top H30 down to the H14. The top of the main target H30 was found at 670.1 m MD/RT (-631.2 m TVDLL). The reservoirs consist of poorly consolidated sand/sandstones between soft swelling clays / claystones. The well TD at 918.3 m MD/RT (-879.4 m TVDLL) within the H14 reservoir.

The well encountered all Mio-Pliocene reservoirs from Top H30 to the H14, with the top H30 being encountered as per prognosis at 670.1 m MD/RT (631.2 m MD/RT), and the well reached TD in the H14 at 918.3 m MD/RT (-879.4 m TVDLL).

H30 and H27 were found to be oil-bearing while H25 was found to be oil and water-bearing, with an ODT at 769 m MD/RT (-731 m TVDLL), and WUT (771 m MD/RT) -733 m TVDLL. OWC is therefore in line with other wells encountered in the Ngiri Field (-733 m TVDLL)

Pressure measurements confirm the disconnection between the H30 and H27-H25 hydrocarbon columns.

The total reservoir quality is good with a total Net sand of 71 m, and average PhiE of 25%.

02N31E-112-1 (Ondyek-1) is the last exploration well drilled by TOTAL E&P Uganda in the Albert Nile Sub-Basin before the expiration of the Exploration Area (EA-1A) license. The well is located in West Nile Area to the West of Lake Albert (1.2 km) and 6.5 km South of Panyimur Town. Ondyek-1 is positioned at the intersection of 2D HR seismic lines TEP12-01-OND (shot point - 2411) and TEP12-02-OND (shot point – 2372) with offset wells Riwu-1 (21.3 km) to North East, Ngiri-1 (16 km), Ngiri-2 (15.4 km) and Ngiri-3 (14 km) drilled in the Central Trend in the East Nile Area.

Ondyek-1 pre-well objectives were to explore the hydrocarbon potential of the Ondyek faulted structural closure, to evaluate the reservoir and seal extension / properties in the area, to recognize the complete stratigraphic sequence and to prove the prospectivity in the deepest part of EA-1A along the western bounding fault, to evaluate source rock potential and maturity in the vicinity of the Albert Lake kitchen in the Albert Nile Sub-Basin.

Ondyek-1 was spudded on 3rd January 2013 with the Caroil-2, and the well reached final total depth (TD) of 1462m MDRT on 31st January 2013.

An acquisition program was performed on this well; conventional logs necessary for formation evaluation were run to solve the uncertainty on reservoir properties, including Wireline formation testing for pressures and sampling performed over the H30 to H15 sequences.

A zero-offset VSP was recorded from TD section to surface for accurate seismic calibration of the well.

A casing shoe integrity and hydro-fracturing constraint LOT were performed at 293 m MDRT (6 m below the 13 ⅜” casing shoe) and at 768 m MD/RT (6 m below the 9 ⅝” casing shoe).

The well was plugged and abandoned after logging.

Operations and results

Ondyek-1 encountered all the prognosed Late Miocene to Late Pliocene reservoir intervals from H30 to H15 and TD’d in the weathered basement (H1). Top H30 was encountered at 862.30 m MD/RT (-833.80 m TVD/LL). The well was drilled to the total depth of 1462 m MD/RT (-1342.4 m TVD/LL). All the reservoir intervals are inter-bedded sequences of unconsolidated sands and clays.

Ondyek-1 well encountered all the prognosed reservoirs from H30 down to the weathered basement H1. All the reservoir intervals from H30 to H1 are evaluated as water bearing. A negligible background gas (0.02 to 0.04 %) was observed while drilling through H30 to H1 reservoirs.

Wireline log interpretation indicates all the reservoirs as water bearing. The formation pressure data align parallel to the regional water gradient (sg: 0.992 g/cc for H30 to H17). Formation fluid sampling from H27 zones confirm the reservoirs as water bearing.

The reservoir section (H30 to H15) is in fair correlation with Ngiri-Kasamene-Wahrindi offset wells in Central Trend.

All the formation tops were encountered at relatively shallower depth than prognosed in the uncertainty range.

02N31E/78-1 (Raa-1) well is one of the first exploration wells drilled by TOTAL E&P Uganda on the Northern Trend of Ugandan Exploration Area (EA-1A) to the North-west of Appraisal Area (EA-1). The well is located on land to the East of the Albert Nile (1.25 km), close to Pakwach Town (4.27 km), and within the Murchison Falls National Park. Raa-1 is positioned on the existing 2D HR seismic line TEP12-02-RAA (shot point - 2202) with offset wells Jobi East-2 (6 km), Jobi-2 (8.3 km) to the South West on the Eastern Trend.

Raa-1 was drilled as a vertical exploration well to target regionally proven reservoir intervals H30, H27, H25 and H15 deposited in fluvio-deltaic to lacustrine environments. The primary objective was to explore the hydrocarbon potential and to evaluate the reservoir with relation to the seal extension along the tilted fault block of the Northern trend.

Raa-1 pre-well objectives were to explore the HC potential of the undrilled Northern trend, to evaluate the Raa tilted fault block structural closure, to recognize the entire sedimentary section in the Northern part of the Albert basin, to evaluate the reservoir and seal extension / properties in the area and to test the prospectivity of amplitudes identified in the area.

Raa-1 was spud on 22nd December 2012 with OGEC RR 600 rig and reached a final total depth at 431 m MDRT. The well was plugged and abandoned on 31st December 2012 subsequent to logging operations.

Operations and results

Raa-1 well encountered all the prognosed Late Miocene to Pliocene reservoir intervals from H30 to H15 and TD’d in the virgin basement (H0). Top H30 was encountered at 229.7 m MDRT (-210.1 m TVD/LL). The well was drilled to a Total Depth of 431 m MDRT (-411.4 m TVD/LL) with a total penetration of 12.1 m into the virgin basement (H0). All the reservoir intervals are inter-bedded sequences of unconsolidated sands and clays.

All the encountered reservoirs from H30 down to the H0 virgin basement are water bearing. No hydrocarbon shows observed in the cuttings while drilling. A negligible background gas (0.01 to 0.02 %) was observed while drilling through H30 to H15 reservoirs.

Wireline log interpretation indicates all the reservoirs as water bearing. The formation pressure data aligns parallel to the regional water gradient. Two distinctly different water gradients were observed (0.993 g/cc for H30-H15 reservoirs and 0.986 g/cc for H37-H35 levels). The formation fluid sampling from H30 and H27 zones confirm the reservoirs as water bearing.

The reservoir section H30 to H15 is in fair correlation with East Nile offset wells. All the formation tops were encountered deeper, except H36 level and the basement which were encountered at a shallower depth than prognosed.

The well was plugged and abandoned.

02N31E-102-1 (Rii-1) was the third exploration well to be drilled by Heritage Oil Limited in Exploration Area 1 of Uganda. The well was drilled as a vertical exploration well on the Rii (Giraffe) structure. This structure is located in the Uganda Exploration Area 1, which is in the western part of the Republic of Uganda near the northern end of Lake Albert. The Rii-1 (Giraffe-1) well is located on land to the north of the Victoria Nile and west of Paraa, within the Murchison Falls National Park area in Nwoya County of Amuru District. The nearest offset wells at the time of drilling were the recent Exploration Area 1 wells Ngiri-1 (Warthog-1) and Jobi-1 (Buffalo-1) drilled by Heritage. The well lies on line 2D Seismic Line HOG-B1-07-12.

The well was spudded on 24th December 2008 and drilled as a vertical exploration well to a total depth of 705m MDBRT in pre-tertiary metamorphic basement on 4th January 2009. The well was suspended as a potential future production well on the 9th January 2009.

Operations and results

02N31E-102-1 (Rii-1) was drilled as a vertical exploration well. The Top Reservoir Seismic Marker was encountered at 436.5m MDBRT, 4.5m low to prognosis, with elevated gas levels seen from 439m MDBRT. Oil shows were seen from sandstones over the interval 436.5m MDBRT to 535m MDBRT; gas levels started to reduce from 526m MDBRT onwards with only ethane and methane being present below 536m MDBRT.

Petrophysical analysis of wireline logs and formation pressure data indicate that there was a gross oil-bearing interval of approximately 89m with net oil pay of approximately 38m. RCI pressure testing and sampling has confirmed the presence of moveable oil, with samples having been recovered to surface, and log interpretation indicates reservoir quality in the pay interval to be excellent. The gross oil interval seen in the well is 89.0m, with an oil water contact seen in logs and calculated from pressure data at 524.7m MDBRT.

02N31E-114-11 (Rii-2) is a vertical appraisal well with a sidetrack for selective coring drilled to appraise the presence of hydrocarbon within the Rii South Panel down-dip of Rii-1. Rii-2 is situated on land within the Murchison Falls National Park in the North Nile Area (~800 m North of Victoria Nile, 106 m to the North of Ramsar Boundary and ~9 km to the South-East from Albert Nile). The surface location is approximately 3.9 km SSW of Rii-1, 6.4 km SSW of Jobi-3 and Jobi-6, 9.3 km SSW of Jobi-1 and 3.4 km NNE of Ngiri-6. Rii-2 is positioned on the 2D Regional Seismic line HOG07-15 Fugro processed Final PSTM dataset, shot point: 2623, CMP-544, Trace-545.

Rii-2 was spudded on 19th January 2014 with EXALO 115 rig and reached final total depth (TD) at 768 m MDRT on 29th January 2014. The pilot hole was logged for correlation for selecting coring points and subsequently plugged for sidetracking.

Operations and results

The Rii-2 vertical well intersected all Miocene to Pliocene reservoirs from Top H30 down to weathered basement (H1). Top H30 was found at 540.1 m MDRT (-526.6 m TVD/LL) and pilot hole well TD was reached 24.2 metres below top H1 at 768 m MD/RT (-754.5 m TVD/LL). The reservoirs are an alternation of unconsolidated sands with soft claystones

The well confirmed the presence of hydrocarbon. The overall sand content in the well is very good with a total net sand of 120 m and an average PhiE = 29%

H30 and H27 are positive; H30 upper has good reservoir properties (PhiE = 26 %). H30 upper was oil and water bearing with an OWC found at -545 m TVD/LL. H27 has very good reservoir characteristics (PhiE = 31 %). H27 was oil and water bearing with an OWC found at -592 m TVD/LL.

From MDT plots, H30, H27 oil columns are vertically disconnected. Two aquifers are seen at well; one in the H30 and another common aquifer from H27 down to H14.

Minor shows were observed at H25 and H15 ultimate top. Other reservoirs in the H25, H15 and H14 reservoirs are encountered water bearing.

Rii-2 appears as an isolated panel, with H30 and H27 oil accumulations being not in communication with the ones of the Jobi-Rii field neither with the ones on Ngiri field.

02N31E-114-11A (Rii-2A) is a sidetrack for selective coring for Rii-2 pilot hole drilled to appraise the presence of hydrocarbon within the Rii South Panel down-dip of Rii-1. Rii-2A is situated on land within the Murchison Falls National Park in the North Nile Area (~800 m North of Victoria Nile, 106 m to the North of Ramsar Boundary and ~9 km to the South-East from Albert Nile). The surface location is approximately 3.9 km SSW of Rii-1, 6.4 km SSW of Jobi-3 and Jobi-6, 9.3 km SSW of Jobi-1 and 3.4 km NNE of Ngiri-6. Rii-2 is positioned on the 2D Regional Seismic line HOG07-15 Fugro processed Final PSTM dataset, shot point: 2623, CMP-544, Trace-545.

Rii-2A sidetrack well was initiated at 474 m MDRT on 3rd February 2014 and reached final total depth (TD) at 755 m MDRT on 14th February 2014. Thereafter open hole logging acquisition was performed. The 7’’ casing was run and set in place with the shoe at 754 m MDRT in preparation for testing. Selective coring was based on the hydrocarbon shows encountered and data acquired in the pilot hole.

A full acquisition program was performed on this well in addition to the conventional logs necessary for formation evaluation, magnetic resonance was run to solve the uncertainty on reservoir properties. • A VSP was recorded for accurate seismic calibration.

Operations and results

Rii-2A was drilled as a sidetrack well for selective coring. A total number of 10 selective cores were cut in the reservoir. The total length of core cut was 51.5m and recovered 42.98m (83.5%). The Rii-2A well intersected all Miocene to Pliocene reservoirs. The reservoirs are an alternation of unconsolidated sands with soft claystones.

The main results of the well confirmed the presence of hydrocarbons. The overall sand content in the well is very good with a total net sand of 120 m and an average PhiE = 29%

H30 and H27 are positive; H30 upper has good reservoir properties (PhiE = 26 %). H30 upper was oil and water bearing with an OWC found at -545 m TVD/LL. H27 has very good reservoir characteristics (PhiE = 31 %). H27 was oil and water bearing with an OWC found at -592 m TVD/LL. From MDT plots, H30, H27 oil columns are vertically disconnected. Two aquifers are seen at well; one in the H30 and another common aquifer from H27 down to H14.

Minor shows were observed at H25 and H15 ultimate top. Other reservoirs in the H25, H15 and H14 reservoirs are encountered water bearing.

Rii-2A appears as an isolated panel, with H30 and H27 oil accumulations being not in communication with the ones of the Jobi-Rii field neither with the ones on Ngiri field.

Well Testing

Well testing operations began on 19th February 2014. Two production tests were done on the H27 and H30 zones and one Mini-Frac + Injection Test + Fall-Off test was done on H30 before the well was plugged and abandoned. Schlumberger was the principal service company on behalf of Total E&P Uganda.

Two (2) production tests on H27 and H30 were performed and one (1) Mini-Frac + Injection Test + Fall-Off test on H30. The perforated intervals TCP #1 H27: 585.0 – 595.0m MDRT and TCP #2 H30: 541.0 – 545.0m MDRT.

The injection test was carried out with viscosified water with polymer (mini-frac test and injection test) and then with fresh water (FES water). The quality of data is good and can be used for further interpretations.

H30 Production test: A progressive cavity pump was used during the whole test. The efficiency of the pump was good. The average production rate during the main flow period was 14.7m3/d (92bpd). The cumulative volume produced was 99bbls, CO2 and H2S were measured to 0% and 0ppm respectively. The oil density is 24.7°API. Dead oil was sampled at the tank with 5 cans of 20 litres. The preliminary interpretation of the data provided a permeability of 2.7D.

H27 Production test: A progressive cavity pump was used during the whole test. The efficiency of the pump was good. The average production rate during the main flow period is 54m3/d (339.7bpd). The cumulative volume produced is 124bbls, CO2 and H2S were measured to 0% and 0ppm respectively. The oil density is 25°API.

Dead oil was sampled at the tank with 5 cans of 20 litres. No smoothing coefficient was applied on the derivative. The preliminary interpretation of the data provided a permeability of 3.6D.

02N31E-104-1 (Til-1) is one of the first exploration wells drilled by TOTAL E&P Uganda in the Eastern Exploration Trend of Ugandan Exploration Area (EA-1A) to the East of Appraisal Area (EA-1). The well is located on land to the North of Victoria Nile within the Murchison Falls National Park. Til-1 is positioned on the existing 2D seismic line HOG-20410-04 (shot point - 2472) with offset wells Mpyo-1 (7.5 km), Mpyo-3 (7.2 km) and Gunya-1 (15.1 km) to the South West on the Eastern Trend.

Til-1 was drilled as a vertical exploration well targeting regionally proven reservoir intervals H30, H27, H25 and H15 deposited in fluvio-deltaic to lacustrine environments. The primary objective was to explore the hydrocarbon potential and to evaluate the reservoir with relation to the seal extension to the North Eastern extremity of the Eastern Trend. The other objectives were to explore the hydrocarbon prospectivity of the Til tilted fault block up-dip Mpyo discoveries, to evaluate the nature of fluids and assess oil quality (biodegradation), to evaluate the hydrocarbon column and potential communication with other offset wells, to establish reservoir facies variation and vertical compartmentalization and to evaluate the reservoir and seal extension in the area.

The well was spudded on 6th December 2012 with OGEC RR 600 Cracow rig and reached a total depth(TD) at 362m MDRT. Drilling operations ended after permanent abandonment on 14th December 2012.

A data acquisition program was performed on this well; conventional logs necessary for formation evaluation were run to solve the uncertainty on reservoir properties. Wireline formation testing for pressures and sampling were performed over the H30 to H1 sequences. A zero-offset VSP was recorded from TD section to surface, for accurate seismic calibration of the well. Look ahead recording was applied to calibrate the area with previous 2D seismic acquisitions in the region. A casing shoe integrity and hydro-fracturing constraint LOT was performed in the top seal at 125 m MD/RT (3 m below the 9 5/8″ casing shoe). No test was performed in the well.

The well was plugged and abandoned after completing the planned data acquisition.

Operations and results

Til-1 vertical well encountered all the prognosed Late Miocene to Late Pliocene reservoir intervals from H30 to H15 and TD in the virgin basement (H0). Top H30 was encountered at 164 m MD/RT (-78.3 m TVD/LL). The well was drilled to the total depth of 362 m MD/RT (-276.3 m TVD/LL) with a total penetration of 24 m within virgin basement (H0). All the reservoir intervals are inter-bedded sequences of unconsolidated sands and clays.

The well encountered reservoirs from H30 down to the virgin basement H0 which are all water bearing. No HC shows observed in the cuttings while drilling. No gas was recorded while drilling. Wireline log interpretation indicates all the reservoirs as water bearing. High resistivity in the reservoir zones was probably related to fresh formation water. Formation pressure data align parallel to the regional water gradient similar to offset wells. The formation fluid sampling from H30 and H15 zones confirms the reservoirs as water bearing. All the formation tops were encountered within +/- 22 m from prognosed depth.

02N31E-89-1(Riwu-1) exploration well was drilled by TOTAL E&P Uganda in the Northern Sub-Basin of Ugandan Exploration Area (EA-1A) to the North-West (1.2 km) of Appraisal Area (EA-1). The well is located on land to the West of Albert Nile (7 km) and close to the Pakwach Town (7.4 km). Riwu-1 is positioned on the existing 2D seismic line HOG07-07 EXT (shot point - 2850) with offset wells Raa-1 (10.5 km), Lyec-1 (15.7 km) to the North-east and Jobi-2 (12.7 km) and Jobi East-2 (14.1 km) to the South-east on the Central trend.

The main purpose of the Riwu-1 well was to explore hydrocarbon potential in the EA-1A Northern sub-basin by drilling the uplifted Western Trend. The pre-well objectives were to explore the potential oil accumulation of the undrilled uplifted Western Trend, to explore the faulted structural closure along the main rift fault, to understand the stratigraphic sequence and prove potential HC migration in the area and to evaluate the reservoir and seal characteristics (extension, properties) in the area. To test the prospectively of amplitudes in the area.

The Riwu-1 well was spudded on 6th December 2012 with Weatherford W721 rig, and reached final total depth at 391m MDRT into basement on 12th December 2012.

Based on preliminary results, a minimal acquisition program was performed on this well; conventional logs necessary for formation evaluation were run to solve the uncertainty on reservoir properties. Wireline formation testing for pressures and sampling was performed over the H37 to H1 sequences. A zero-offset VSP was recorded from TD section to surface for accurate seismic calibration of the well. A casing shoe integrity and LOT was performed in the top seal at 172 m MDRT. No test was performed in the well.

The well was plugged and abandoned on 19th December 2012 after completing the planned data acquisition.

Operations and results

Riwu-1 well encountered reservoirs from H30 down to the virgin basement H0 were identified as water bearing. No HC shows observed in the cuttings while drilling. No relevant gas was observed while drilling through H30 to H15 reservoirs. Wireline log interpretation indicates all the reservoirs as water bearing. Different aquifer pressure regimes were encountered in the well. Formation fluid sampling confirmed the reservoirs as water bearing. The reservoir section (H30 to H15) is in fair correlation with East Nile offset wells. All the formation tops were encountered deeper, except for the basement which was encountered at a shallower depth than prognosed.

The well was plugged and abandoned after logging the 8 1/2” section to well TD.

02N31E-79-1 (Lyec-1) well is one of the first exploration wells drilled by TOTAL E&P Uganda on the Central Trend in Ugandan Exploration Area (EA-1A) to the North (950 m) of Appraisal Area (EA-1). The well is located in Murchison Falls National park to the East of the Albert Nile (5.46 km) and 8.5 km South-east to the Pakwach Town. Lyec-1 is positioned on the 2D HR seismic line TEP12-01-LYE (shot point 2360) with offset wells Raa-1 (5.48 km) to the North-west, Jobi East-2 (3.93 km), Jobi-2 (8.33 km) and Jobi East-1 (8.48 km) to the South-west on the Central Trend.

The main objectives of Lyec-1 were to test the presence of hydrocarbons within the H30-H15 sequences up-dip Jobi East-2 discovery , to establish the nature of fluids and assess oil quality (biodegradation) , to evaluate hydrocarbon column and potential communication with other offset wells, to identify possible trapping mechanism towards the basin edges, to evaluate the quality of reservoir intervals at H30, H27, H25 and H15 and to evaluate the reservoir and seal extension in the area.

Lyec-1 was spudded on 28th December 2012 with OGEC K900 rig, and the well reached TD of 290 m MDRT on 1st January 2013. The well was temporarily plugged and suspended with a view to perform a well test.

An acquisition program was performed on this well; conventional logs necessary for formation evaluation were run to solve the uncertainty on reservoir properties, magnetic resonance, density and resistivity imagery logs were also run. Wireline formation testing for pressures and sampling was performed over the H30 to H15 sequences. A zero-offset VSP was recorded from TD section to surface for accurate seismic calibration of the well. A casing shoe integrity and hydro-fracturing constraint LOT was performed in the top seal at 133 m MD/RT (3 m below the 9 5/8″ casing shoe).

Operations and results

Lyec-1 was drilled as a vertical exploration well targeting geological equivalents of regionally proven reservoir intervals H30, H27, H25 and H15 deposited in fluvio-deltaic to lacustrine environment. The primary objective was to explore the hydrocarbon potential up-dip the Jobi-East field within the Central Trend of EA1A, and to evaluate the reservoir with relation to the seal extension along the Jobi-East tilted fault block. The well encountered all the prognosed Late Miocene to Late Pliocene reservoir intervals from H30 to H15 and TD’d in the weathered basement (H1).

Top H30 was encountered at 161.6 m MD/RT (-136.3m TVD/LL). The well was drilled to the total depth of 290 m MD/RT (-264.7 m TVD/LL) with a total penetration of 7 m within weathered basement (H1). All the reservoir intervals are inter-bedded sequences of unconsolidated sand and clay.

The reservoir intervals H30, H27 and H25 are oil bearing. Hydrocarbon shows were observed in the cuttings while drilling from 161.6 m MD/RT to 208 m MD/RT. A maximum gas peak of 2.61 % was recorded at 200.4 m MD/RT while drilling through the reservoir section.

Wireline log interpretation indicates reservoir intervals H30, H27 and H25 as oil bearing. Formation fluid sample recovered from H30 at the depth of 162.5 m MD/RT confirms the mobile oil phase. Reservoir section (H30 to H15) is in fair correlation with Jobi East offset wells.

All the formation tops (MD/RT) were encountered at a relatively shallower depth than prognosed within a range of -7.6 to -22.7 m.

Well Testing

Well testing operations began on 30th April 2013 using ZPEB Rig 26. Two production tests were done on the H25 and H27U zones. The third test initially planned on the H30 was cancelled following the results of the DST#2 test. Schlumberger was the principal service company on behalf of Total E&P Uganda.

The well test objectives were to determine fluid mobility and the short-term productivity index of the well (transient PI), to collect fluid samples, to determine permeability and skin of the productive interval and to determine the existence of any near well bore reservoir heterogeneities and limits

Two (2) production tests on H25 and H27U on perforated intervals TCP #1C H25: 198 – 202m MDRT and TCP #2 H27U: 183 – 186m MDRT. The preliminary results obtained were very uncertain, due to the data quality. Additional investigation may be necessary to reduce current uncertainties. The well was plugged and abandoned after well test operations.

Kanywataba-1 well was planned and drilled by CNOOC Uganda Limited as a vertical wildcat exploration well with the primary target reservoir being the Kingfisher equivalent sandstones close to the H07 seismic marker (Lower Pliocene to Upper Miocene). The nearest offset wells and analogues to Kanywataba are the Kingfisher field & wells, about ~40 km to the North East. The reservoirs are expected to be deltaic and fluvial influenced sandstones, equivalent to the Kingfisher reservoirs. Other offset wells in the area are the Turaco wells, ~20km to the North North West. Kanywataba-1 well is positioned on line 2D Hog-2010-5 and Hog-2010-10. The primary target horizons are upper Miocene-lower Pliocene series (H07-H30), secondary is top sandstone of upper Pliocene series (H32). The drilling would end to the pre-Tertiary basement.

The pre-well objectives were to prove up an active hydrocarbon system in this part of the basin, to test the equivalent Miocene-Pliocene oil bearing sands that have already encountered at the Kingfisher wells, 40kms to the North East, to be drill the wildcat well to a minimum of 2000m MD or further as required depending on drilling constraints and results, to obtain PVT and atmospheric samples during wireline logging operations in 12.25" & 8.5" holes using standard RCI with probe to be used, to determine the pressure regime within any reservoir sections encountered and identify potential contacts where possible, to obtain quality samples of formation water to assist with petrophysical analysis, to obtain VSP data for seismic calibration, to drill into basement to establish seismic control and to suspend the well for future re-entry.

Kanywataba-1 is situated at the high position of the structural ridge of Kanywataba. This area has a basement of pre-Tertiary metamorphic rock overlain by complete strata. From upper to lower, this well encountered Holocene, Pleistocene, Pliocene, Miocene and pre-Tertiary basement, and completed at depth 30m below the top basement.

Kanywataba-1 well was spudded on 17th May 2012 with OGEC K-900 rig and reached a final total depth at 2105m MDRT about 30m into the basement. The plug and abandonment were completed on 28th June 2012.

Operations and results

Through the entire well sections, only weak gas indicator was seen, and logging interpretations are all water or tight layers. A number of 12 RCI sample points were planned in the well section 1300-1600m and 6 sample points were taken successfully, and the other 3 points were filtrate, 3 points were dry. The fluid nature of the samples was determined by neutron density mirror image reflection. There was no hydrocarbon indication in the well section 1300-1600m, no gas anomalies either.