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Understanding the petroleum system evolution in underexplored areas: a case study from the Namibe Basin (Angola).

Abstract

Identification of petroleum system elements and timing of hydrocarbon generation are primary tasks in exploration, underpinning all the activities of the oil and gas value chain. However, assessing petroleum system evolution in underexplored areas is often difficult due to the lack of legacy data and, consequently, subsurface geological knowledge. Therefore, effort should be made in order to integrate as many evidences as possible from the basin and nearby areas. The Namibe Basin is the southernmost sedimentary basin in Angola and developed as part of the Cretaceous South Atlantic rift, whose hydrocarbon province hosts some of the most oil-rich sequences in the world. No hydrocarbon wells have been drilled in the basin, but a working petroleum system is demonstrated by bitumen in pores and fractures of Pre- and Post-Salt intervals at different onshore localities along the basin strike. Organic-rich sections likely represent the lateral equivalents of offshore source rocks. The origin of the observed oil, represented by the bitumen, could relate to: (1) generation within an onshore petroleum system; (2) local forced maturation related to regional volcanism; and (3) migration from offshore. The aim of this study is to identify the source rock stratigraphic interval/s by correlating the bitumen and the organic-rich sections using biomarkers and locate the hydrocarbon kitchen area/s by evaluating the thermal maturity of onshore key stratigraphic sequences and offshore offset wells. This will allow to test each of the initial hypotheses and to model the evolution of the petroleum system/s in the basin to guide further exploration.