Aspects of the Hydrocarbon Potential of the Coals and Associated Shales and Mudstones of the Mamu Formation in Anambra Basin, Nigeria

Abstract

Coals and associated shales and mudstones of the Mamu Formation in Anambra basin were examined for their hydrocarbon potentials by subjecting them to total organic carbon (TOC) and Rock-eval Pyrolysis analyses. The TOC results range from 45.56 to 67.68 wt. %, 0.07 to 5.65 wt. % and 0.12 to 4.46 wt. % for the coals, shales and mudstones respectively, suggesting that the sediments contain appreciably high quantity of organic matter that can generate hydrocarbon. Ranges of Hydrogen Index (HI) and Genetic Potential (GP) for the coals, shales and mudstones are 167 to 327 mg/g and 114.99 to 159.54 mg/g, 50 to 288 mg/g and 2.85 to 15.66 mg/g TOC, 41 to 239 mg/g and 0.54 to 10.96 mg/g respectively. Tmax and Calculated vitrinite reflectance (% Ro) of sediments range from 412 to 432 ^oC and 0.26 to 0.62 respectively. The Rock-eval data suggested poor to very good source rocks in the sediments, with the shales as good source rocks, the mudstones as poor to good source rocks and the coals as very good source rocks. The predominant organic matter types in the sediments are kerogen type II/III and type III which are oil and gas prone. The coals are dominated by kerogen type II/III while the shales and mudstones are dominated by kerogen type III. Thermal maturity from Rock-eval data indicated that the sediments are immature with respect to hydrocarbon generation and generally at low level conversion. The coals and the associated shales and mudstones of Mamu Formation are therefore capable of generating oil and gas at appropriate maturity.

Keywords: Mamu Formation, Coals, Shales, Mudstones, Hydrocarbon generation, Kerogen, Thermal maturity