Numerical Simulation of Improved Gas Production from Oceanic Gas Hydrate Accumulation by Permeability Enhancement Associated with Geomechanical Response

In the Shenhu Area of the South China Sea, although some numerical studies are conducted on the gas production at well SHSC-4, the geomechanical responses have not been taken into account, and the associated impact of permeability enhancement on gas production has not been thoroughly investigated. In this study, pTOUGH+HYDRATE V1.5 coupled with the RGMS is applied to account for geomechanical responses. Based on actual geological conditions, the reservoir model has five layers: the hydrate-bearing layer (HBL), the three-phase layer (TPL), the free gas layer (FGL), the overburden, and the underburden. The numerical results match the trial production data, validating the numerical model. The analysis shows that gas production from the FGL contributed the most (72.17%) to the cumulative gas production (V_g), followed by the TPL (23.54%) and the HBL (4.29%). The cumulative water-to-gas ratio (R_wgT) gradually decreased during gas production, with the HBL exhibiting the highest value. Permeability enhancement can improve gas production, with the FGL being the most responsive to such enhancement. It increased V_g by 87% and reduced R_wgT to 85%. To achieve more realistic production schemes and better enhance energy recovery, it is advisable to conduct numerical investigations that incorporate geomechanical considerations due to the intricate nature of hydrate-bearing sediments.