Main constraining factors and distribution prediction of lacustrine hydrocarbon source rocks in Yueguifeng Formation in Lishui-Jiaojiang Sag

The Yueguifeng Formation is the main source rock of Lishui-Jiaojiang Sag that formed in the period of strong fault filling of the Yueguifeng Formation, with strong tectonic segmentation, relatively enclosed sedimentary environment, and unclear development characteristics of lacustrine source rock in mainly four sub-sags. To clarify the development conditions and spatial distribution of the source rocks of the Yueguifeng Formation in each hydrocarbon-rich sub-sag, and further guide the oil and gas exploration in the area, the data of logging and coring in geophysics, geochemistry, and paleontology were used based on the dynamic life cycle process of the lake basin evolution. We proposed that the four factors, in temporal order, of early-stage fault activity rate, middle-stage parent rock property and the shielding conditions, and late-stage volcanic activity, jointly constrained the development of high-quality source rock in the four major sub-sags. Under the best geological knowledge, based on multi-attribute neural network deep learning, the spatial distribution of middle-deep lacustrine hydrocarbon source rocks was depicted quantitatively. Based on the development mechanism of high-quality source rocks and the distribution range of medium-deep lacustrine source rocks, the development of high-quality source rocks in the four major sub-sags was evaluated comprehensively. The results indicate that Jiaojiang A Sub-sag is a Class Ⅰ hydrocarbon rich sub-sag, Lishui A and Lishui C Sub-sags are Class Ⅱ sub-rich hydrocarbon sub-sags, and Lishui B Sub-sag is Class Ⅲ hydrocarbon-generating sub-sag.