Experimental Investigation of Time-Dependent Geomechanical Behavior of Caprocks from California's Central Valley for Carbon Capture and Storage Applications

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🔬研究者:Provides new experimental data and insights on caprock creep behavior, useful for geomechanical modeling and CCS simulation research.

Carbon Capture and Storage (CCS) is an important strategy for reducing anthropogenic carbon dioxide emissions, particularly for industrial and energy sectors where direct emission reduction is difficult. The long-term success of geological CO2 storage depends on the ability of the storage reservoir and overlying caprock to maintain containment over extended time scales. Although gas-producing shales have been extensively studied in unconventional reservoir applications, time-dependent geomechanical data for caprocks remain limited, especially for formations relevant to CCS development in California's Central Valley. This limitation creates uncertainty when selecting geomechanical input parameters for long-term CCS simulation studies. This study investigates the time-dependent geomechanical properties of caprock samples from California's Central Valley and evaluates whether gas-producing shale data is useful as direct proxies for caprock behavior in CCS applications. Caprock samples from the San Joaquin Basin and Sacramento Basin were tested and compared with gas-producing shale samples from the Wolfcamp Formation in Texas and the Utica Formation in Ohio. Hydrostatic and triaxial creep experiments were conducted using a RTR-1000 GCTS triaxial apparatus. The measured deformation data were used to determine pre-creep and post-creep bulk modulus, Young's modulus, Poisson's ratio, and power-law creep parameters. X-ray diffraction was used to characterize mineralogical composition, and Micro-CT imaging was used to examine internal fracture features in caprock samples before and after creep testing. The results show that the caprock samples exhibit distinct time-dependent geomechanical behavior compared with the gas-producing shale samples. In general, the caprock samples have smaller bulk modulus and Young's modulus, larger Poisson's ratio, and greater power-law creep parameters (B and n). The San Joaquin Basin caprock samples show greater stiffness than the Sacramento Basin caprock samples, while the Sacramento Basin samples show more creep compliance. Micro-CT observations suggest that sustained loading may promote closure of pre-existing microfractures and compliant pore spaces. This observation is consistent with the increase in stiffness after creep for several caprock samples. Overall, the results indicate that gas-producing shale properties should not be used as direct substitutes for caprock properties in CCS simulation studies without site-specific validation. Caprock-specific time-dependent geomechanical measurements are necessary for improving the reliability of long-term geomechanical models and assessing caprock integrity in geological carbon storage systems.

• openalex https://doi.org/10.25740/bv671th3945first seen 2026-06-06 05:00:56