Objective Shale oil and gas in the Chang 7 Member of the Yanchang Formation in the Ordos Basin have become a hot spot in oil and gas exploration and a key replacement area. This paper analyzes the heterogeneity characteristics of organic matter in shale oil and gas and its influence on mineral composition, gas content, and pore structure, aiming to provide basic data for the further development of shale oil and gas.

Methods Taking the Chang 7 Member of the Yanchang Formation in Yan'an area of the Ordos Basin as an example, this study comprehensively uses measured data such as core data, logging data, and organic geochemistry, and adopts experimental methods including microscopic thin-section observation, scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray fluorescence diffraction (XRF) to analyze the heterogeneity characteristics of organic matter in the shale reservoirs in the study area. Mathematical methods are also used to clarify the relationships between organic matter and reservoir mineral composition, gas content, and pore structure.

Results The study shows that the Chang 7 Member in this area has strong heterogeneity, and organic matter is closely related to mineral composition, gas content, and pore structure.

Conclusions Organic matter exhibits strong heterogeneity in both microscopic and macroscopic distributions, with the strongest heterogeneity in the Chang 7₃ sub-member. The total organic carbon (TOC) content has a strong correlation with parameters such as mineral composition, gas content, and pore structure. The content of mineral components affects the heterogeneity of organic matter distribution, while the heterogeneity of organic matter also has a certain impact on the gas content and pore structure of shale reservoirs. The source rocks in the Chang 7₃ sub-member have a large thickness, high TOC content, and high hydrocarbon generation potential, indicating good development prospects.