Buffalo could be Uganda's largest oil field

The Buffalo-1 discovery on Uganda's Block 1 could become the country's largest oil field, said operator Heritage Oil Ltd., Calgary.

By OGJ editors
HOUSTON, Dec. 16 -- The Buffalo-1 discovery on Uganda's Block 1 could become the country's largest oil field, said operator Heritage Oil Ltd., Calgary.

Buffalo, which could be larger than Kingfisher field on Block 3A, cut a 123-m gross hydrocarbon column with 43 m of net hydrocarbon pay, Heritage said (see map, OGJ, Feb. 11, 2008, p. 36). The rig is moving to drill the Giraffe-1 exploration well.

Heritage estimated the midrange gross contingent and prospective resource at 118 million boe at Kingfisher and 32 million boe at Kingfisher North in September. That was before successful completion of the Kingfisher-3 well earlier this month, when Heritage called Kingfisher, which has moved into the development phase, the largest oil discovery in sub-Saharan East Africa.

Kingfisher-3, drilled downdip on the southwest part of the Kingfisher structure, found hydrocarbons 100 m structurally higher than expected. It found oil in all three Kingfisher reservoir intervals over a gross hydrocarbon bearing interval of 110 m with net pay of up to 40 m.

Buffalo discovery
Buffalo-1, off the northeast end of Lake Albert, is 500 m from the crest of the structure. TD is 637 m.

Wireline logging and formation pressure measurements indicate 28 m of net oil pay in the principal oil-bearing reservoir section overlain by 15 m of additional net hydrocarbon pay that contains gas.

Downhole pressure testing and sampling confirmed the presence of movable oil that has been recovered to surface, and log interpretation indicates that reservoir quality in all pay zones appears to be excellent, Heritage said. It suspended the discovery as a potential future production well.

The gross oil and gas columns seen in the well are 75 m and 48 m, respectively, and there is potential for the gross oil column of the accumulation to be significantly larger than reported because no oil-water contact was encountered.

Management believes that Buffalo is the leading discovery in Block 1 and the Butiaba area to date. Based on seismic interpretation, further exploration and appraisal drilling could prove up a substantial accumulation of oil, Heritage said.

Block 1 has numerous other prospects mapped on more than 600 line-km of seismic data shot in the past 18 months. All are characterized by similarly encouraging seismic amplitude anomalies as seen over the Buffalo and Warthog prospects, and all represent further prospects and leads which constitute additional multiple drilling targets within the block.

All 17 wells drilled in the Albert basin in Uganda the past 3 years have found hydrocarbons.

Heritage and Tullow Oil PLC each holds 50% interest in Blocks 1 and 3A in Uganda.

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