THMC Fully Coupled Model of Natural Gas Hydrate under Damage Effect and Parameter Sensitivity Analysis

Abstract

In order to study the influence of damage on the gas production of natural gas hydrate, a multi-physical field theoretical model considering damage effect and coupling thermal-hydraulic-mechanical-chemical (THMC) was established by theoretical analysis and numerical simulation. The THMC model establishes the relationship between the elastic modulus of hydrate sediment and hydrate saturation during the whole process of hydrate decomposition. The THC (thermal-hydraulic-chemical) and THMC fully coupled models not considering or considering the damage effect were compared and analyzed, and the reliability of the THMC fully coupled model was verified. On this basis, the deformation, permeability and damage of hydrate sediments under different initial hydrate saturations and different depressurization amplitudes, as well as the hydrate gas production rate and cumulative gas production, are analyzed. The results showed that higher initial hydrate saturation inhibited the development of damage, maintained stable gas production and increased cumulative gas production. Larger depressurization promoted damage and increased cumulative gas production, but it was easy to cause stability problems.