In this research, we developed a numerical simulator predicting methane hydrate (MH) dissociation and production behavior in using grout material. This simulator solves the governing equations of the mass conservation for methane, water, MH, grout material and grout material hydrate components, and that of the energy conservation simultaneously. These governing equations as well as constitutive equations were derived assuming the following. (1) MH is dissociated and produced by the depressurization method with endothermic effect. (2) The sand layer collapses as the pore pressure and MH saturation decreases, resulting in the decrease in the permeability. (3) The grout material is injected with water from the production well prior to the depressurization or after dissociating some parts of MH. (4) The injected grout materials flow only in the water phase. (5) The injected grout materials react with water component during the curing period to become grout material hydrates with exothermic effect. (6) When the content of grout material hydrate exceeds a critical value, the sand layer is strengthened, which prevents the sand layer from collapsing.
After coding this simulator, we compared the calculation results by my simulator with those by MH21-HYDRES, a numerical simulator developed by the MH21-S R&D Consortium in Japan, and verified that this simulator worked accurately for the case of the MH dissociation by the simple depressurization. As a result of this verification, it was confirmed that the calculation function of this simulator is functioning correctly.
Then, we predicted the MH dissociation and production performances assuming the application of the grout material injection method before starting the depressurization and after dissociating some parts of MH. The results of this case simulation revealed that (1) the gas production became much smaller if the collapse of the sand layers and associated sand problems were taken into consideration, (2) the grout material injection could suppress the decrease in a gas production associated with sand problem and (3) the grout material injection after dissociating some parts of MH was more effective creating a room for injecting more grout material.
