Effect of Microfractures on the Seepage Characteristics of Hydrate Bearing Rocks under Confining Pressure

Summary The technology of methane production through the replacement of carbon dioxide in gas hydrates without their decomposition involves the cyclic injection and extraction of gas. Under cyclic pore pressure, predicting changes in permeability is a crucial factor that determines the overall efficiency of this technology. The classical approach to determining permeability under loading is the use of a power law, where the exponent is often cited by many authors as the coefficient of sensitivity of permeability to loading. However, the nature of this coefficient remains poorly understood. Some studies have attempted to establish a relationship between the exponent of the power equation and the porosity or permeability of rocks based on statistical dependencies. Nevertheless, these attempts have not provided a comprehensive understanding of the true nature of the law governing permeability changes. This paper presents the results of comparative modeling of the deformation of a porous medium with and without microcracks. Numerical modeling of permeability change with constant and nonlinear Young’s modulus was performed. Constant Young’s modulus is typical for monolithic samples. The presence of microcracks in samples determines significant deformations and nonlinearity of Young’s modulus. Comparison of numerical modeling results with experimental results showed a high degree of convergence.