Coupled Evolution of Oil Content and Pore Structure of the Qingshankou Formation Shale, Songliao Basin, Northeastern China: Insights from Thermal Simulation Experiments

Oil content estimation and pore characterization of shale are crucial for identifying sweet spots in shale plays. Despite extensive research, the correlation between retained hydrocarbon characteristics and pore evolution in shale with thermal maturity remains controversial. This study employs an integrated approach, combining thermal simulation experiments with multiple analytical techniques, to investigate organic geochemical characteristics and pore structure evolution across different maturity stages. The results demonstrate that thermal maturity plays a significant role in evolution and synergistic changes in oil content and pore characteristics. Within the optimal maturity of 1.20%-1.60%, shale has three key favorable characteristics: (1) elevated gas-to-oil ratios, (2) enhanced fluidity of retained hydrocarbons, and (3) well-developed pore networks that facilitate efficient hydrocarbon. Combined with the geological conditions of the Songliao Basin, we identify that the shale oil in the Gulong Depression with an optimal maturity range of 1.20%-1.60% is the most promising exploration target.