QIAO Y, SONG D Y, LIU W Q, et al. Pore structure characteristics and evolutionary patterns of coal-measure shale in the Shanxi Formation, eastern Ordos Basin[J]. Journal of Henan Polytechnic University (Natural Science), 2024, 43(5): 53-66.

doi:10.16186/j.cnki.1673-9787.2022030039

Received:2022/03/15

Revised:2022/04/18

Published:2024/07/31

Pore structure characteristics and evolutionary patterns of coal-measure shale in the 

Shanxi Formation, eastern Ordos Basin

QIAO Yu1,  SONG Dangyu1,2,  LIU Weiqing1,  YU Zhen1

1.School of Resources and Environment， Henan Polytechnic University， Jiaozuo  454000， Henan， China;2.Collaborative Innovation Center of Coalbed Methane and Shale Gas for Central Plains Economic Region， Henan Polytechnic University， Jiaozuo  454000， Henan， China

Abstract: Objectives This study aims to clarify the characteristics and evolutionary patterns of pore structure in coal-measure shale.  Methods X-ray diffraction, rock pyrolysis, scanning electron microscopy, low-pressure CO²/N² adsorption, and high-pressure mercury intrusion experiments were conducted to characterize the pore structures of various lithofacies in the Shanxi Formation coal-measure shale in the eastern Ordos Basin.  Results The findings indicate that the Shanxi Formation primarily comprises silica-rich argillaceous shale lithofacies (A-1), siliceous/argillaceous mixed shale lithofacies (M-2), and clay-rich siliceous shale lithofacies (S-3). Mesopores are the main contributors to pore volume, accounting for over 65%, while micropores are the primary source of reservoir specific surface area, contributing more than 62%. The S-3 shale exhibits larger total pore volume and specific surface area, averaging 0.036 2 cm³/g and 35.15 cm²/g, respectively, whereas the A-1 shale has smaller values, averaging 0.026 6 cm³/g and 21.39 cm²/g, respectively. Organic matter influences the specific surface area of shale by controlling micropore development. Additionally, clay minerals positively affect the shale’s specific surface area, while pyrite promotes the pore structure of both M-2 and S-3 shale. The pore evolution of A-1 shale is most significantly impacted by compaction and clay mineral transformation, while S-3 shale pores are notably affected by cementation, organic hydrocarbon generation, and dissolution. M-2 shale pores display characteristics of diagenetic evolution from both A-1 pores and S-3 shale. Conclusions These results provide valuable references and insights for studying the pore structure of coal-measure shale in the Ordos Basin.

Key words:lithofacies type; pore structure; diagenesis; coal-measure shale; eastern Ordos Basin