Pore structure of continental shale reservoirs in Lower Jurassic Ziliujing Formation, northeastern Sichuan Basin

Abstract

The accumulation and enrichment of shale gas were significantly influenced by the pore structure of shales. In this study, thin section observation, Argon ionization-scanning electron microscopy analysis, physical property test, mercury injection-N2 adsorption combination, X-ray diffraction whole rock analysis and X-ray diffraction clay mineral analysis were carried out to study the pore structure characteristics of continental shale of Lower Jurassic Ziliujing Fromation, northeastern Sichuan Basin. Results showed that: (1) In the Ziliujing Formation of the northeastern Sichuan Basin, the pores were mainly parallel plate and slit ones, and ink bottle pores were also developed. The average value of specific surface area of shale was 4.031 m2·g-1, the average value of total pore volume was 93.88×10-4 mL·g-1, and the micro pores were dominated by meso pores (2-50 nm). (2) The specific surface area of shale is positively correlated with the volume of micro pores and meso pores, but not with the volume of macro pores. In clay minerals, illite-montmorillonite and chlorite are positively correlated with shale specific surface area and micro pore volume. The TOC content of continental shale has a certain influence on the macro pore volume, and has a positive correlation with it to a certain extent. (3) The pore structures of shale are similar in the Da'anzhai section of Ziliujing Formation. According to the difference of shale pore structure, the Dongyuemiao section can be divided into two parts: the northwestern and the southeastern. The Dongyuemiao section in the southeast is similar to the Da'anzhai section in pore structures.

Keywords

• continental shale reservoir
• pore structure
• ziliujing formation
• lower jurassic
• northeastern sichuan basin