TOC content quantitative prediction in organic-rich shale
Wang Jian1, Shi Wanzhong1,2, Shu Zhiguo3, Xu Qinghai1, Zhang Xiaoming1, Xu Zhuang1
1. Faculty of Earth Resources, China University of Geosciences (Wuhan), Wuhan, Hubei 430074, China;
2. Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education, China University of Geosciences (Wuhan), Wuhan, Hubei 430074, China;
3. Research Institute of Petroleum Exploration and Development, Jianghan Oilfield Branch Co., SINOPEC, Wuhan, Hubei 430223, China
Abstract:Industrial development of shale gas has been achieved in the Fuling area, Sichuan Basin. Total organic carbon (TOC) content is one of the most critical indexes for organic matter abundance evaluation and hydrocarbon generation potential in shale. TOC content evaluation in source rocks from well logging can make up for the insufficiency of rock cores. We propose in this article an approach of TOC content quantitative prediction. Based on measured TOC content and well logging data from Wufeng-Longmaxi formation in the Well A, Fuling, the most sensitive parameter to TOC is found out with multi-parameter optimization, cross-plot analysis, multiple regression analysis, and ΔlgR method. Then an optimal fitting statistical equation between the sensitive parameter and TOC is established, and an empirical formula is obtained for TOC calculation. Finally a TOC volume is calculated with the optimal fitting statistical equation and 3D seismic poststack inversion to realize TOC content quantitative prediction. The results reveal that the predicted TOC values highly coincide with the measured values.Calculated TOC content values of the target members are between 0.5%~5.15% and the first member is 1.9%~5.15%. The TOC planar distribution characteristics obtained by 3D seismic inversion are consistent with the measured and calculated TOC data from 4 wells in the area. Our application shows that the proposed TOC prediction approach is accurate and reliable, and could be used for shale gas exploration and evaluation in the area.
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