A History of Successful Exploration in Exploration Area 2, Albertine Graben, Uganda

Chas Sheen and Paul L. Burden
Exploration, Tullow OIl, Cape Town, South Africa

In 2001 Hardman and Energy Africa formed a Joint Venture to explore EA2.Several puzzles were present prior to exploration beginning.

Seeps; numerous documented seeps at the Rift Margins implied an active hydrocarbon system. Was this good news (active migration) or bad news (a leaky system)?

Structure; Waki-1 well drilled in 1938 after several shallower wells indicated the high point of a marker horizon, but did this mean that the well was optimally located for the reservoir section encountered at 1160m. Did any other substantial structures exist?

The main challenges relate to operating in the area.

First Phase of Seismic on Lake Albert in 2003; This was considered to be the best way to cover a large area to determine the prospectivity of the area. Conducting a marine survey on a lake in a land locked country in central Africa for a small independent Australian operator was a major challenge. Syracuse University were renowned for their interest in Rift Basins and their ability to carry out such an undertaking and were contacted to assist. These data indicated significant structural potential, including shallow amplitude anomalies conforming to structure. Drilling the most attractive prospect deep (~50m) water was a challenge that could not be overcome at this stage and the plan was to acquire further seismic onshore adjacent to the large offshore lead.

Second Phase of Seismic onshore 2005; Building a road down the 400m escarpment in order to complete this phase was also a major challenge. Resultant seismic data indicated several 3-way dip closures against the Rift Basin Fault. 2 wells were decided upon to fully test the play.

Drilling on Land 2005/6; Another road with reduced gradient was required in order to bring in the rig. Positive results ensured continuation of the project with follow up and appraisal drilling continuing into 2007/8.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery