Geophysical studies in lamu embayment to determine its structure and stratigraphy

Abstract

The area of study comprises part of one of the hydrocarbonpotential basins in Kenya; the Lamu basin. Major transgression and regression cycles dominated the area during different Mesozoic times. These depositional cycles together with tectonics associated with rifting and separation of Gondwanaland and also of Madagascar from Africa and the occasional doming of central Kenya resulted in a highly deformed basement with thick sedimentary cover due to subsidence and tilting. The study of the Geophysical anomalies in the area, indicated by gravity and seismic data as well as the study of 6 deep wells drilled within the area revealed that the major tectonic disturbances of the area were caused by basement complex block faulting. Bouguer anomalies indicate major basement variation in the northwest of the study area. Towards the coast, it becomes featureless with a two fold gravity gradient. This is attributed to the thinning of the continental crust and the presence of oceanic crust below the coastal sediments The analysis of seismic data has shown that structures in the area are fault controlled. The major fracturing is mainly along a NNW-SSE direction. A minor trend in a NE-SW direction has bean confirmed. It has also confirmed the presence of rounded closed highs that represent potential drilling locations. Well logs have shown that the area has good source reservoir and caprocks that could combine very well with the closed highs to accumulate oil and gas pools.