深层气携热辅助开采浅层水合物的数值模拟OA

Shallow hydrate bearing formation and deep conventional gas reservoir usually co-exist and exhibit a vertically o-verlapping symbiotic relationship.In the process of gas production,the heat carried by the deep conventional gas can be used to assist gas extraction from shallow hydrates.In this study,dynamics of gas production from hydrate was investigated and compared using three different production methods via numerical simulation,including pure depressurization,wellbore heating assisted depressurization,and deep conventional gas heat-carrying assisted depressurization.The heat utilization rate of deep conventional gas was analyzed,and the production parameters for heat-carrying extraction were optimized.The results indicate that the cumulative gas production from pure depressurization can reach to 505×104 m3 after 2000 d of a horizontal well produc-tion.Moreover,when assisted with wellbore heating and deep conventional gas heat-carrying,the cumulative gas production can be increased to 551×104 m3 and 538×104 m3,respectively.The hydrate gas production enhancement from the deep conven-tional gas heating can be more evident in the mid-to-late stages of the production,and only 2.2%of the heat can be utilized by hydrate dissociation.An orthogonal design method was employed to determine an optimal combination of the operation parame-ters for hydrate gas production assisted by the deep conventional gas heating method.If the daily gas production rate from the deep conventional gas layer is set at 30×104 m3 with an abandoned pressure of 8 MPa,and the bottom hole pressure of the shal-low gas hydrate layer is set at 3 MPa,with a pressure reduction rate of 5 MPa/d,the cumulative gas production from hydrate can be increased by 66%in comparison with pure depressurization,and the heat utilization can be increased 10.7%.