Control of Physical Properties by the Matching between Rock Components and Pore Structure in Shale Reservoirs of the Permian Lucaogou Formation, Jimusar Sag

Shale oil reservoirs are extremely tight, making it fundamental to evaluate their physical properties for exploration and development efforts. These properties are closely linked to the rock components (RC) and pore structure (PS). The significant complexity and heterogeneity inherent in RC and PS pose considerable challenges for assessing the physical properties of these reservoirs. In specific depositional environments, a matching relationship between the RC and PS exists. Identifying this relationship and associating microscale PS attributes with macroscale physical properties can expose substantial variations within shale oil reservoirs, aiding in the selection of optimal layers for exploitation and improving the development efficiency. This study focuses on the shale oil reservoirs of the Lucaogou Formation in the Jimusar Sag, marked by mixed-source sedimentation. It employs experiments such as X-ray diffraction, total organic carbon measurement, low-temperature nitrogen adsorption, mercury injection capillary pressure, and scanning electron microscopy to characterize the RC and PS. Based on these experiments, the research analyzes the matching relationship between RC and PS in the shale oil reservoirs and the connection between microscale PS and macroscale physical properties, highlighting the control of physical properties, by RC and PS. The findings reveal that pore types in these shale oil reservoirs predominantly consist of small pores and mesopores. Small pores, developed within K-feldspar, quartz, and clay minerals, are chiefly dissolution pores; mesopores occur between dolomite or plagioclase grains and are characterized by a regular pore morphology. Porosity is governed by the presence of micro-, meso-, and macropores, while permeability is principally influenced by meso- and macropores. The study indicates that rocks with a higher content of dolomite and plagioclase, such as dolomitic siltstone, silty dolomite, and feldspar silt-fine sandstone, possess comparatively superior physical properties. This established relationship between RC and PS in this study offers a reference for the efficient development of the Lucaogou Formation shale oil reservoirs and can serve as a foundation for research into the fluid–solid interaction and flow characteristics in porous media.