Analysis of oil exploration plays in Anza Basin from a trap-type perspective

Abstract

The Anza basin is a sedimentary basin in North Eastern Kenya. The first wells in the Anza basin were drilled in 1976. Chevron and Esso drilled Anza-1 and Bahati-1 wells in the southern part of Anza Basin. Since then 11 wells have been drilled in the Anza Basin. There have been oil and gas shows in some of the wells. This study employed play analysis which is a technique used for petroleum resource exploration and assessment. In play analysis a basin is divided into prospective resource areas called plays. In this study these prospective areas were divided into these prospective resource areas based on the trap types identified. The play is a useful analytical concept that allows the analysis to be sensitive to the physical processes involved in the entrapment of oil and gas and in the discovery of oil and gas accumulations. The main objectives of this study were to delineate plays types based on trap types identified in the area, to determine the stratigraphy of the area and to identify and delineate structures within the area. This was done by the interpretation of seismic sections, refining well log information and by integrating information from interpreted seismic sections and final well log information so as to determine the stratigraphy of the area. ArcView GIS (Geographical Information Systems) and SMT (Seismic Micro Technology) Kingdom Suite were the main tools that were used in achieving the objectives of this study. The trap types identified included both structural and stratigraphic traps with shale being the sealing rock and siltstone and sandstone as the major reservoir rocks. Several structures including faults, folds, unconformities and pinch-out were also identified and delineated. The stratigraphy of the area was also determined by refining the information that was available from the three wells (Ndovu-1, Duma-1 and Kaisut-1) that are in the study area.