Millimeter-scale fine evaluation of shale oil content and pore structure heterogeneity and its significance

Summary Millimeter-scale fine evaluation of shale oil content and pore structure heterogeneity is of great significance for shale oil enrichment. Taking medium-high maturity shale in the Qingshankou Formation in Gulong Sag of Songliao Basin as an example, the mechanism of difference in reservoir property and oil content between different lithologies was revealed by high performance microzone X-ray fluorescence spectroscopy, rock pyrolysis, analysis of total organic carbon content, low-temperature nitrogen adsorption before and after oil washing based on millimeter-scale microdrill sampling, high pressure mercury injection by conventional sampling and other experimental analysis. It includes the distribution of different minerals and organic matter, pore structure characteristics, free hydrocarbon content and residual oil occurrence characteristics. It is clear that the mineral fraction and organic matter content are the main factors affecting the reservoir and oil content of shale. When the clay mineral content and organic matter content are higher, the pore volume and specific surface area of shale are larger, the free hydrocarbon content is more, the oil content is lighter, the residual oil content is more, and the proportion of movable oil is higher. Therefore, it is recommended to take organic-rich and clay-rich shale as the first choice for exploration.