Enhancing gas production and CO2 sequestration from marine hydrate reservoirs through optimized CO2 hydrate cap

The invasion of formation water during marine hydrate production gravely affects gas productivity. CO2 hydrate caps effectively inhibit water invasion while sequestering CO2, which is considered an excellent prospective application. However, forming field-scale artificial CO2 hydrate caps remains a global challenge. This study proposed an innovative method for forming an artificial CO2 hydrate cap. The fracture length, injection time, production pressure, and production well distance, which are all factors that affect sealing capacity and production enhancement, were optimized. Results indicated that the sealing capacity exhibited a trend of initially increasing and subsequently decreasing with fracture length. The injection time was positively correlated with the sealing capacity and was sufficient to seal both vertically and horizontally once it reached 4 years. In addition to sequestering CO2, the CO2 hydrate cap enhanced gas production by 146.56% and reduced water production by 37.47% compared to direct depressurization. CO2 invasion occurred when the well spacing was too close, while being distant was not favorable for pressure propagation and heat utilization by the CO2 hydrate cap. This method simultaneously achieves multiple goals for energy and environmental, providing essential implications for the future commercial application of marine hydrates.