Delineation of petroleum plays in the offshore Lamu Basin, Southeast Kenya

Abstract

Despite having evidence of a working petroleum system, the offshore Lamu Basin of Southeastern Kenya remains a frontier hydrocarbon province. This study employed a play-based exploration approach to delineate petroleum plays in the offshore Lamu Basin using integrated interpretation of gravity data, 2D seismic data, and selected well information. Traps/prospects and plays were interpreted using seismic facies analysis, reflector terminations, seismic attributes and sequence stratigraphic (system tract) relationships. Due to the limitation of 2D seismic data, seismic attributebased delineation of stratigraphic traps was not extensively applied. The study aimed at delineating petroleum plays of offshore Lamu Basin by identifying the structural and stratigraphic traps in the area and grouping them into petroleum plays. Regional gravity analysis reveals a structurally complex basin architecture characterized by deep depocenters and basement highs that strongly influence sediment distribution and hydrocarbon migration pathways. Based on shared source rocks, common tectonic settings, and similar trap types, twelve (12) distinct petroleum plays were delineated. The structural plays include Upper Cretaceous anticlinal play, Oligocene anticlinal play, Miocene faulted anticlinal play, Oligocene faulted anticlinal play, Upper Cretaceous rollover anticline play, Oligocene flower structure play, Oligocene-Miocene positive flower structure play, a multi-interval volcanic edifice play intruding from the Upper Cretaceous through the Oligocene-Miocene succession, and a Miocene tilted fault blocks play. The stratigraphic plays of the offshore Lamu Basin comprise Upper Cretaceous and Paleocene pinch-out plays, dominated by pinch-out traps, as well as a Miocene channel play characterized by channelized reservoir traps. Hydrocarbon charge for the delineated plays is inferred to originate primarily from Upper Cretaceous (Campanian) and Eocene marine source rocks, with migration facilitated by faultcontrolled pathways and carrier beds. Structural plays are the most prominent and well-defined on the available data, while stratigraphic plays provide additional exploration potential but with higher uncertainty. The results demonstrate that the offshore Lamu Basin hosts a diverse portfolio of viable petroleum plays, controlled by the interaction of tectonic evolution and stratigraphic architecture. This study has provided a coherent geological framework to guide future exploration efforts and highlights the need for basin modelling to further reduce exploration risk and refine prospect evaluation.