Hydrocarbon Source Rock Potential of the Lacustrine Black Shale Unit, Mamfe Basin, Cameroon, West Africa

Abstract

The potential for conventional and/or unconventional hydrocarbon exploration requires the presence of organic-rich, thermally mature rock units containing oil or gas-prone kerogen. Thick black, organic rich shale intervals are well exposed along roadside cuts and river banks at several localities in the eastern part of the Mamfe Basin. Earlier described as anoxic lake bottom deposits, these fine grained rocks constitute the probable pod of active source rock in this basin and belonging to the middle stratigraphic unit of the three that make up the basin’s sedimentary fill. Samples collected from representative outcrop sections (Etoko mile 21, Bachuo Ntai, and Satom Bridge) in the study area were subjected to geochemical analytic techniques; Total Organic Carbon (TOC), Rock-Eval Pyrolysis and Vitrinite reflectance (%Ro) values were calculated. TOC data obtained range from 1.06% to 16.10% indicating good to excellent hydrocarbon generative potentials, Rock-Eval Pyrolysis data plotted along Kerogen Types I, II and III with oil and gas generative potentials. 4 out of 9 samples fall within the oil window from the calculated %Ro while temperatures corresponding to the peak of kerogen pyrolysis (Tmax) and Production Index (PI) for the 9 samples range from 398oC to 463oC indicating that the organic matter (OM) are immature to post mature.The black shale unit of this part of the basin therefore contains very high amounts of good to excellent quality of thermally matured organic matter which can produce and expel oil and gas respectively.