Experimental analysis of the synergistic effect between geothermal temperature and depressurization rate in the geothermal-assisted production of natural gas hydrates

To uncover the collaborative mechanism between Depressurization (DP) strategies and geothermal conditions in Natural gas hydrates (NGHs) production, this study systematically explored the exploitation characteristics of the depressurization method coupled with Geothermal energy (GE) assistance. Through the design of comparative experiments with varying Geothermal temperatures (GT) and depressurization rates, the focus was placed on analyzing the influence of temperature-pressure coupling laws on hydrate decomposition characteristics, heat transport efficiency, and economic benefits. The experimental results show that compared with the single depressurization method, geothermal assistance increases the production efficiency by 48.97 %. Further analysis of the impact of different geothermal temperatures on production reveals that production efficiency exhibits a nonlinear growth trend, initially increasing and then slowing down with the rise in geothermal temperature, reaching an optimal value (0.188 h−1) at 45 °C, indicating an apparent temperature threshold effect. This was attributed to an insufficient utilization (in the hydrate layer) of the heat released from the circulating water from the deep layer with a higher temperature. The study on the characteristics of different depressurization rates and geothermal temperatures suggests that increasing the depressurization rate enhances heat transfer and gas production efficiency by intensifying heat release during the constant-pressure phase. Conversely, an excessively slow depressurization rate limits extraction efficiency due to insufficient heat release. The synergistic mechanism between depressurization rate and geothermal temperature uncovered in this study provides critical theoretical support for the efficient utilization of geothermal energy and the improvement of natural gas hydrate extraction efficiency and economic feasibility.