Hydrocarbon enrichment conditions and distribution in continental shale, West Liaohe Sag, Bohai Bay Basin

We analyzed the hydrocarbon enrichment conditions in shale in the West Liaohe Sag of Bohai Bay Basin, and discussed the distribution features and pattern of shale oil and gas in continental rift basins, based on the tests of a large number of shale samples. The shale in the third and fourth members of Paleogene Shahejie Formation in the West Liaohe Sag has a large total thickness, wide distribution, good continuity, high TOC content (average 2.67%), and medium maturity (0.4%-1.5%). Organic matter is mainly sapropelic, and partially of humic type. The shale developed considerable pores, mostly intergranular and dissolution pores, and tectonic (with some interlayer) fractures. Favorable physical properties of reservoirs and high hydrocarbon content made the study area a good place for shale oil and gas enrichment. Controlled by sedimentary facies, organic matter type and thermal maturity, the West Liaohe Sag mainly yields shale oil, and regionally shale gas. From the bottom of the fourth member to the upper part of the third member of the Shehejie Formation, we found shale oil and gas, shale oil, and shale gas in turn. In the basin center, we mainly found shale oil, while on the slope we found interbedded shale oil and gas.