Genetic mechanism and distribution model of correlation between shale oil and conventional oil about the third member of Shahejie formation in Bonan sag, Jiyang depression, Bohai Bay Basin

In order to explore the correlation distribution mechanism between shale oil and conventional oil, clarify the correlation distribution law between shale oil and conventional oil, and guide the collaborative exploration practice, taking the third member of Shahejie Formation in Bonan sag, Jiyang depression, Bohai Bay Basin as an example, based on the comprehensive application of drilling, logging, seismic and a large number of analysis and test data, taking the transmission conductor connecting shale oil and conventional oil as the breakthrough point, the influence of fluid pressure evolution environment on the transmission capacity of the transmission conductor was discussed, and the distribution mechanism of shale oil and conventional oil was clarified. The results show that, based on the principle that conventional oil and shale oil generated by source rocks in the same unit are only accumulated in this unit, the third member of Shahejie Formation in Bonan sag can be divided into six oil accumulating units. Shale oil and conventional oil resources in the same oil accumulating unit have different correlation about shift from one to another. Shale oil and conventional oil resources in different oil accumulating units are different on the basis of normalization. According to fluid inclusion test, fault activity analysis and development degree of high permeability sand body, there are three kinds of fluid pressure fields in the third member of Shahejie Formation in Bonan sag, which are open pressure field, semi closed pressure field and closed pressure field during the key reservoir forming period. In the open fluid pressure environment, advection dominates the long-distance migration of corrosion products, acid corrosion has obvious pore increasing effect, and the physical properties and transport capacity of the transport body are high. In the closed fluid pressure environment, diffusion dominates the short-distance migration of corrosion products, and the corrosion products precipitate near the site to block the roar channel. The physical properties of the transport body are low and the transport capacity is weak.The difference of transport capacity of conductor in open and closed fluid environment controls the difference distribution of shale oil and conventional oil. Conventional oil is relatively enriched in open fluid pressure environment, shale oil is relatively enriched in closed fluid pressure environment, and conventional oil and shale oil are relatively enriched in semi closed fluid pressure environment. © 2022 Central South University of Technology. All rights reserved.