| The Bongor Basin,located in southwest Chad,is one of the largest petroliferous basins within the Central and Western African Rift System?WCARS?.Based on detailed geochemical analyses of 45 rock samples and 22 oil samples in the Lower Cretaceous of the Bongor Basin,this study systematically described the geochemical characteristics of source rocks and oil samples from the Bongor Basin.In addition,the genetic classification of oils and oil-source correlation were discussed.The analysis of geochemical characteristics of source rocks shows that organic abundance in source rock samples is high,belonging to good-excellent source rocks as a whole.These source rocks are characterized by the dominance of type I-II1kerogen.The thermal evolution degree of source rocks in different formations are different:Most of the source rocks of Lower Cretaceous P and M formations are mature,while the source rocks of Lower Cretaceous R and K formations are still immature.Based on the molecular geochemical characteristics of source rocks,the results show that the organic matter may orginate from a mixed source of lower aquatic and terrigenous organic material and these sediments were deposited in a sub-oxic lacustrine environment.The crude oils are generated by source rocks of mature stage.A high similarity in characteristics of molecular composition in oil samples reveals that these oils can be considered to be derived from the same oil family.The result of oil-source correlation shows that the crude oils have the best genetic relationship with source rocks of M and P formations,but the contribution of mature source rocks from K Formation in the center of the basin should not be negated. |
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