HYDROCARBON GENERATION AND MIGRATION FROM BARREMIAN – APTIAN SOURCE ROCKS, NORTHERN ORANGE BASIN, OFFSHORE WESTERN SOUTH AFRICA: A 3D NUMERICAL MODELLING STUDY

A 3D numerical modelling workflow was applied to the Barremian—Aptian source rock interval in a shelfal lower slope area of northern Orange Basin, offshore western South Africa. The main objective investigate timing hydrocarbon generation and migration. Hydrocarbon migration has previously been investigated south basin by relating gas escape features with structural elements as seen on seismic sections, but pathways are still poorly understood. study based data from three exploration wells (AO-1, AE-1 AF-1) together 42 2D sections totalling 3537 km length, cube covering an 750 sq. km. Modelled formation temperatures increase north were consistent downhole at well locations. However, there is variation between measured modelled values vitrinite reflectance (VR), especially Turonian Cenomanian intervals. VR than within section area, suggesting that erosion affected thermal maturity sediments. interval, higher VR. Uplift, increased hinterland sediment transport coastal areas resulted progradation Basin fill. This heat flow pulse maturities area. Modelling results show began central part 116 Ma reached peak Late Cretaceous (65 Ma). about 110 expulsion efficiency 0.77. At present day, ∼100% transformation reactive kerogen into hydrocarbons taken place random Albian reservoirs. oil likely influenced hydrodynamic factors down-dip (westwards), towards deeper-water, more distal parts basin. Gas saturation reactivated listric fault, which saturated 93 Ma, declined ∼15% 65 Ma. decrease linked uplift African margin fault reactivation re-migration gas. Despite uncertainties associated petroleum systems modelling, provides insight contributes de-risking future this