Contribution of Organic Matter Pores to Reservoir Capacity of Highly Heterogeneous Shale Reservoirs: A Case Study from Qianfoya Formation, Sichuan Basin

Organic matter pores are key storage spaces in shale reservoirs, particularly in continental condensate gas systems characterized by high pressure, advanced maturity, and unique hydrocarbon adsorption. However, the heterogeneity of internal pores driven by variations in pore shape, size, and organic matter development complicates the quantitative evaluation of their reservoir contributions. In this study, SEM, CT, FIB-SEM, and subcritical gas adsorption techniques were used to characterize organic pores. The results revealed that organic matter contributes 13.2% of the pore volume and 9.7% of the pore-specific surface area in the micromesopore range and 23.8% of the pore volume and 2.9% of the pore-specific surface area within the macropore range. The extractable organic matter is the main matrix that generates the pores. Organic pores are locally developed, providing excellent communication channels and oil and gas adsorption sites, which improve storage space locally. When there are many organic pores, the physical properties of shale reservoirs are significantly improved, especially in terms of the shale porosity. However, the permeability remains extremely low, which facilitates the formation and retention of shale oil and gas in the reservoir.