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Exploration History of the Butiaba-Previous HitVictoriaNext Hit-Nile Play, Albert Rift Basin, Uganda

Burden, Paul A.1
(1)Exploration, Tullow Oil South Africa, Cape Town, South Africa.

Exploration of the northern areas of the Albert Rift Basin straddling the Previous HitVictoriaNext Hit Nile River in Exploration Area 1 (EA-1) and the northern portion of Exploration Area 2 (EA-2) began in 2007 with the acquisition of a fairly sparse grid of 2-D seismic by Tullow, the operator of EA-2 and Heritage, operator of EA-1.

Interpretation showed large NW-SE trending faults cross-cut by secondary E-W trending faults. The intersection of the two fault trends combined with structural dip towards the SW led to the definition of a number of triangular shaped fault traps each bounded by two faults with monoclinal dip to the SW towards a potential 'source kitchen' beneath Lake Albert. Some of these prospects were supported by amplitude anomalies at various levels in the interval just above the base of the rift-fill. Prospects identified included Ngege, Kasamene, Kigogole, Nsoga, Ngiri (Warthog), Rii(Giraffe) and Jobi(Buffalo).

The first boreholes drilled within the area were Ngege-1, Kasamene-1 in mid 2008 by Tullow. The former was a minor oil discovery in Upper-Pliocene fluvio-alluvial reservoirs. the latter was a more promising discovery in high quality fluvial channel sandstones in the same stratigraphic interval. Kasamene-1 was sidetracked and the reservoir cored. This was followed by another discovery, Kigogole-1, before drilling activity switched to EA-1.

The first well to be drilled by Heritage was Ngiri-1 in EA-1 south of the Previous HitVictoriaNext Hit Nile. This well was a promising discovery similar to Kasamene-1. Activity then moved to the north of the Previous HitVictoriaNext Hit-Nile and the most significant discovery so far was made at the Jobi-1 and Rii-1, drilled at the end of 2008. These wells intersected the same large oil accumulation.

Tullow commenced drilling in mid 2009 in EA-2 and made further discoveries at Nsoga-1, Wahrindi-1 and Ngara-1 and also started an appraisal drilling program with successful wells drilled at Kigogole-3 and 5, Nsoga-5, Kasamene-2, 3 and 3A and Ngiri-2.

In 2010, 7 appraisal wells were drilled in EA-2 in the Kasamene and Kigogole/Nsoga areas whilst in EA-1 two wells were drilled, Ngiri-2, a successful appraisal of the Ngiri-1 discovery, and a new discovery at Mpyo-1.

Exploration by Tullow and Heritage over the past 3 years has opened up a major new oil play in the Previous HitVictoriaTop-Nile region. An extensive appraisal/development programme including more seismic acquisition and further drilling is ongoing. First oil production is expected by 2012.

 

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.