Fault Seal Versus Hydrodynamics in the South Lokichar Basin, Kenya

In the northern part of the South Lokichar Rift Basin of Kenya the main reservoir is the LKT68 fluvial sandstone. Exploration and appraisal wells that have drilled the main regional closure in this reservoir encountered a connected oil column. However, the water pressure gradients from the different wells are offset and have a shingled pattern. This pattern of pressure data could indicate the presence of sealing faults within the aquifer, and interpretation of 3D seismic reflection data shows that the LKT68 reservoir within the Greater Etom closure is cut by normal faults. However, these faults are not believed to provide internal barriers within the culmination due to their limited strike length and throw. The pattern of shingled aquifer gradients suggests that a pressure gradient within the aquifer (hydrodynamics) could provide a valid alternative hypothesis to explain these observations. The Hubbert (1953) equation has been used to construct a tilted free-water level surface from the aquifer pressure gradient. This model offers an explanation for why the existing oil discoveries in this area are apparently under-filled, and also indicates that there is potential for additional oil to be present in higher quality axial reservoir facies on the eastern side of the closure.