Sedimentary characteristics of fine-grained sediments and conditions of shale oil accumulation in e1f2 member of funing formation, jinhu sag, china

Shale oil and gas plays an increasingly important role in unconventional energy. The sedimentary characteristics of fine-grained sediments are closely related to the enrichment of shale oil and gas. Organic-rich shale is well developed in the Cenozoic continental lacustrine basin of Jinhu Sag, Subei Basin. Taking the E(1)f(2) member developed in Paleocene as an example, the shale developed with large thickness and wide area has high exploration value. Finegrained shale oil sediment is a hot research topic in the world. Fine-grained sediment is an important material basis for shale oil source and an important carrier for shale oil accumulation. By means of core observation, trace element measurement and geochemical index analysis and testing, this paper systematically analyzes the characteristics of sediments and sedimentary environment in the study area and their controlling effects on shale oil and gas. It is concluded that the sedimentary period of E(1)f(2 )member belongs to the environment of semi-dry heat to dry heat, and the water salinity is from semi-brackish water to salt water. The main origin of clay minerals is chemical deposition. Silty material is mechanically precipitated; Organic matter is the result of biological or biochemical, chemical and mechanical deposition. The carbonate minerals are mainly precipitated by chemical and biochemical processes, and all kinds of fine grained sediments belong to delta front, prodelta, shallow lake and deep lakesemi-deep lake subfacies. The second step is to evaluate source rocks based on TOC detection of core samples, chloroform asphalt "A" detection and rock pyrolysis index analysis. Combined with the shale oil production data, it is concluded that the favorable shale oil lithofacies combination is the shale segment containing silty and limy matter. Finally, it is concluded that the next priority shale oil exploration areas in Jinhu sag should focus on the subsag of the western slope belt of the plane and the E(1)f(2)(2) and E(1)f(2)(3) sub-members of the upper E(1)f(2) member longitudinally. These research results point out the direction for the next key shale oil exploration field in Jinhu Depression, and can also provide reference for the shale oil exploration in other continental lacustrine basins in the world.