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. CO 2 hydrate caps effectively inhibit water invasion while sequestering CO 2 , which is considered an excellent prospective application. However, forming field-scale artificial CO 2 hydrate caps remains a global challenge. This study proposed an innovative method for forming an artificial CO 2 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 CO 2 , the CO 2 hydrate cap enhanced gas production by 146.56 % and reduced water production by 37.47 % compared to direct depressurization. CO 2 invasion occurred when the well spacing was too close, while being distant was not favorable for pressure propagation and heat utilization by the CO 2 hydrate cap. This method simultaneously achieves multiple goals for energy and environmental, providing essential implications for the future commercial application of marine hydrates. [Display omitted] • A novel method for forming field-scale CO 2 hydrate cap is proposed. • Optimal fracture length and injection time are suggested for sufficient sealing cap. • Favorable production well spacing under the CO 2 hydrate cap is revealed. • Sequestering CO 2 while increasing gas production and decreasing water production. [ABSTRACT FROM AUTHOR]