--> Why Not Both Conventional and Unconventional Exploration in Sub-Saharan Africa?

AAPG Annual Convention and Exhibition

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Why Not Both Conventional and Unconventional Exploration in Sub-Saharan Africa?


Conventional exploration typically progresses through the classic sequence of petroleum system identification, definition of trap, reservoir, seal and timing, and finally drilling and production operations. North American unconventional exploration has followed conventional in established basins, building on petrophysical data in the target source/reservoir interval and ambient pressure/ stress information from a myriad of conventional wells, to produce remnant hydrocarbons using directional drilling and hydrofracking techniques. Data from the conventional provides first-order controls on orientation and stimulation design of unconventional projects. Despite conventional production from several onshore basins, there has been little unconventional activity across Africa. The density of unconventional-supporting data is thin. Yet Africa has numerous prospective basins with Paleozoic through Cenozoic (potential and realized) plays. Like eastern North America, the geology consists essentially of a vast expanse of Phanerozoic epi-cratonic basins that overly Precambrian crystalline basement. In both cases there are fringing late Paleozoic fold belts, broad foreland basins, and interior block-faulted terranes. Differences include the extent of crystalline basement exposure, some young and active intracratonic volcanic provinces, and the East African Rift System in Africa; North America carries a lower to mid- Paleozoic sedimentary section that reflects more extensive marine flooding. From late Carboniferous onward, however, the evolution of the continental interiors is similar. The similarities suggest that Africa could ultimately develop an indigenous unconventional industry, but conventional plays must mature before the future is clearer. Knowing the criteria for successful unconventional development, African conventional and unconventional (shale and CBM) plays may progress simultaneously, feeding each other's progress. Downhole data may be supplemented by innovative use of geodynamic inferences from tectono-structural and regional sedimentological data. We present results of a detailed, kinematically realistic overlay for the Purdy Memorial Project ‘Exploration Fabric of Africa’, highlighting previously hidden potentially conventional-unconventional coupled onshore plays. One example lies in northeast Namibia where new interpretations suggest hidden basins under Etendeka basalts and Kalahari sands.