Geochemistry and oil-gas generation modeling of the Late Cretaceous shales from the Chad (Bornu) Basin, Northeast Nigeria

摘要

Late Cretaceous Fika Formation shale was collected and analyzed from six wells in northeastern Nigeria's Chad (Bornu) Basin. The characteristics and the oil and gas-generating potential of the source are discussed based on combined geochemistry investigations and basin models. The abundance of marine phytoplanktonic-bacteria and land-plant suggested by biological markers indicate that the kerogen in the Fika shale Formation is a mixture of Types II and III, which is not compatible with the current low Rock-Eval HI findings of less than 200 mg HC/g TOC. The chemical and optical maturity parameters suggest that the Fika shales throughout the studied wells are in the early maturity stage of the oil window near the gas window point. Therefore, thermal maturation is the critical factor that significantly reduces the original HI values and modifies Types II and III to produce oil and gas.