Geochemical Characterization of Source Rock and Modeling of Hydrocarbon Generation of the Cretaceous Fika and Gongila Formation in the Chad Basin, North Eastern Nigeria

摘要

The Nigerian Sector of the Chad Basin has been the major focus for hydrocarbon exploration due to the recent hydrocarbon discoveries in the adjacent blocks in Chad and Niger Republic in the Chad Basin. But so far no success could be achieved, the hydrocarbon potentials and petroleum system of the study area is not fully understood. In this study, organic geochemical analysis of samples from Fika and Gongila formation in Faltu-1 and Herwa-1 well have been carried out and the results were integrated into basin modeling in order to have a better understanding into the thermal and burial history and timing of hydrocarbon generation. The TOC for the studied samples show a low to moderate values of 0.25-1.72wt.% and moderate to good from 0.4-4.46wt.% in Faltu-1 and Herwa-1 well respectively, hydrocarbon potentials (S1+S2) are negligible in almost all the samples, but some good intervals are seen with values (2.45, 2.99, 3.62 and 6.61) mg/g. The HI values are within the range of 50-150 mgHC/gTOC which indicate the kerogen as mainly type III. The Vitrinite reflectance values VRr ranges from 0.63-1.15%VRr, suggesting that the studied samples are within the oil window which is in agreement with the pyrolysis T_(max) values which ranges from 284-438℃. The modeling results suggest that the thermal and burial history of the studied wells have attained the hydrocarbon generation stage. In Herwa-1 well, the oil window fall within Fika and upper part of Gongila Formation in the early Cretaceous and Gas window in the lower part of Gongila and Bima Formation in the Late Cretaceous. However, in Faltu-1 well the Cretaceous sediments are seen within the oil window in Fika, Gongila and Bima, but the upper part of the Fika formation are within the immature stage while the lower part of Bima formation fall within the Gas window in the Late Cretaceous. This modeling result is in agreement with the organic geochemical analysis of the studied wells.