ABSTACT

Twenty-eight shale and carbonaceous shale samples were collected from four outcrops in Nkporo, New Netim, Ekenkpon and Mfamosing Formations of the Calabar Flank, Nigeria. The source rock potential of the samples was determined using Rock-Eval analysis. The vitrinite reflectance measurements of the samples were taken using Zeiss standard universal reflected microscope. All the shales analyzed contained the minimum of 0.50wt.% and 2.00mg/g of Total Organic Carbon (TOC) and Petroleum Potential (PP) respectively of organic matter required to serve as good source rock for oil and gas. The petroleum potential of the Cretaceous units (Albian-Campanian Formations) of the Calabar Flank, Southeastern Nigeria was assessed by Rock-Eval pyrolysis. The TOC values range from 0.07 to 9.34 wt. % (averaging 2.41 wt. %). The PP and hydrogen index (HI) values range from 0.05 to 34.84 mg HC/g rock and 40.00 to 444.00 mg HC /g respectively. These values indicate that the sediments have gas and oil generating potential. The organic matter is predominantly gas prone (mostly type III and mixed type III/II). The level of thermal maturity deduced from the production index (0.04 to 0.63), calculated vitrinite reflectance of 0.10 to 0.66 %Ro and Tmax values between 338 and 439oC suggest that the shale and carbonaceous shale samples are thermally immature to marginally mature with respect to petroleum generation. Despite the source characteristics portraying moderate to high TOC values and immature to marginally mature; expulsion may have started or yet to get to more maturity stage before oil generation could be enough for expulsion.