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Lithofacies and geophysical quantitative prediction of Madingo Formation marine hydrocarbon source rocks in the Lower Congo Basin, West Africa


Due to the limited drilling wells and oil-based mud pollution, the distribution of the most important marine source rocks in Campanian-Eocene Madingo Formation in the Lower Congo Basin still not fully understood. In our study, an integrated analysis of microscopic sedimentology (thin section, SEM, X-ray diffraction and major and trace element analysis), logging facies, organic facies and back propagation (BP) neural network has been used to deduce the lithofacies, GR curve cycles and distribution of high quality marine hydrocarbon source rocks in the study area. From the research finished yet, we have found some interesting phenomenon of the Madingo Formation, including: (1) Six different hydrocarbon source rock lithofacies have been identified (including the silt, radiolarian enriched, phosphatic, foraminiferan enriched, cinereal and clayey fine-grained lithofacies); (2) The GR curve cycles show the development stage of source rocks corresponds to organic blooming period and the maximum flooding period with 3 stages; (3) The biogenic deposit containing biosilicon, upwelling sediment containing phosphate rock, suspension sediment enriched with siliceous clastic particles, and bottom current sediment with graded bedding are developed in the marine source rocks from Madingo Formation; (4) Back propagation neural network methods has good prediction and correlation coefficient between the predicted and measured TOC content. The paleogeographic background with high productivity and good preservation conditions is the favorable area for high quality marine source rocks. Researching into the characteristics and distribution of high quality marine source rocks will help to better understand the genetic mechanism of marine source rocks related to passive continent margin.