Coupled temperature field model of gas-hydrate formation for thermal fluid fracturing

Thermal fluid fracturing, which helps in improving the heat and mass transfer efficiencies by creating fractures in the gas-hydrate formation, is a new method of developing hydrate reservoirs. However, conventional fracturing-temperature models cannot be used to accurately simulate the temperature fields because of the effect of hydrate decomposition. In this study, a coupled temperature-field model for thermal fluid fracturing is developed considering the effects of the changes in the hydrate decomposition enthalpy and the formation permeability on the heat and mass transfer. The accuracy of the proposed model is verified by comparing the simulated results with the experimental data found in literature. The simulation results show that the hydrate decomposition region appears like “a long and narrow bullet”. Compared to the conventional fracturing temperature model, the loss rate calculated using the proposed model is significantly different in the first one-third portion of the fracture. The effect of the hydrate decomposition on the fracture wall temperature is the greatest, followed by those of the hydrate formation and fracture. The temperature differences with respect to the aforementioned effects are 8, 2-8, and 1-3 °C, respectively. This model provides a more accurate method of determining the temperature for hydrate formation fracturing.