Study on Rock Mechanical Characteristics of Reservoir and Caprock in Medium-deep Gas Storage with Different Lithologies

doi:10.11885/j.issn.1674-5086.2025.12.02.04

Abstract

Abstract: In order to address the differences in mechanical properties of reservoir and cap rocks in middle and deep UGS, this paper selects mudstone, shale, sandstone, and dolomite cores from four UGS (P, M, X, S) and systematically compares their mechanical properties through uniaxial, triaxial, and fatigue compression experiments. The results are as follows: 1) The mechanical strength and deformation resistance of shale in UGS X are weaker than those of cap mudstone of UGS P. The compressive strength and elastic modulus of dolomite in UGS X are much higher than those of sandstone, and its compressive strength can reach more than twice that of sandstone. 2) For UGS with the same sandstone, the deeper the burial depth, the stronger the compressive strength and deformation resistance, and the strength increase of dolomite due to confining pressure is the greatest. Comparison of mechanical parameters of sandstone and mud stone in P UGS, mudstone has slightly higher strength and deformation resistance than sandstone. 3) An increase in burial depth and a decrease in porosity and permeability can significantly enhance rock strength, with a positive correlation between elastic modulus and compressive strength. Fatigue experiments show that the strength of mudstone in deep UGS only decreases by 10% after 1 000 injections, while the strength fluctuation of mud stone in middle UGS reaches 20%. The deep cap rock is more suitable for high-pressure alternating loads. 4) Microstructure analysis reveals that dolomite has high strength due to dense intergranular cementation, while sandstone's porous structure and weak cementation result in weaker mechanical properties. The research results provide experimental support for long-term safe operation of UGS.

Key words: underground gas storage, rock mechanics, uniaxial compression experiment, triaxial compression experiment, lithological differences

CLC Number:

TE822

DUAN Bin, WU Haitao, HAN Dongliang, ZHAO Yao, WANG Miao, ZHANG Ziyu. Study on Rock Mechanical Characteristics of Reservoir and Caprock in Medium-deep Gas Storage with Different Lithologies[J]. Journal of Southwest Petroleum University(Science & Technology Edition), 2026, 48(4): 45-58.

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