双井周期注CO2联合降压法开采天然气水合物分析OA北大核心CSTPCDEI

Different from the simple CO2 storage,the CO2 replacement method can meet the dual demands of natural gas hydrate(hereinafter referred to as hydrate)production and carbon storage when it is used to produce hydrate.To ensure the safe and efficient hydrate production while improving the CO2 storage ratio,this paper takes the typical hydrate in the South China Sea as the research object to establish a reservoir-scale thermal-hydraulic-mechanical-chemical field coupled numerical model of hydrate injection and production according to the idea of dual-well cyclic CO2 injection assisted hydrate depressurization production method.Then,the continuous,intermittent,and cyclic injection production schemes are compared with the single-well depressurization production scheme,and the stimulation effect of CO2-assisted hydrate depressurization production is simulated and analyzed.Finally,different injection schemes are compared from aspects of CO2 recovery and storage,and the feasibility of hydrate method in CO2 storage is explored.And the following research results are obtained.First,CO2 injection in the neighboring well can reduce water production rate and alleviate geological subsidence caused by depressurized production.Second,compared with cyclic injection,intermittent injection can promote the formation of CO2 hydrates in the reservoir and enlarge the high-temperature zone near the injection well,which facilitates hydrate dissociation near the production well.Third,the continuous injection enhances the production of dissociated gas,while the dual-well injection and production diminishes the dissociation extent of methane hydrate.Fourth,CO2 injection in the dual-well injection and production is divided into rapid injection,inversion,and slow injection stages,and the dual-well intermittent injection scheme demonstrates the highest CO2 injection efficiency.In conclusion,the dual-well intermittent CO2 injection assisted depressurization method can achieve safe and efficient hydrate production while providing a significant carbon storage effect.It is a potential approach to achieve commercial hydrate production and contribute to the realization of dual-carbon goals.The research results are of theoretical significance to guide hydrate production and CO2 geological storage.