Self-adaptive gas flow and phase change behaviors during hydrate exploitation by alternate injection of N_(2) and CO_(2)  

作　　者：Bo-Jian Cao Yi-Fei Sun Hong-Nan Chen Jin-Rong Zhong Ming-Long Wang Ming Wang Chang-Yu Sun Guang-Jin Chen 

机构地区：[1]State Key Laboratory of Heavy Oil Processing,China University of Petroleum,Beijing,102249,China [2]School of Chemistry and Chemical Engineering,Changsha University of Science&Technology,Changsha,410114,Hunan,China

出　　处：《Petroleum Science》2024年第3期2120-2129,共10页石油科学（英文版）

基　　金：financially supported by the National Natural Science Foundation of China;China(Nos.22378424,22127812,U20B6005,52004136);the Science Foundation of China University of Petroleum,Beijing(No.2462023BJRC017);Hunan Provincial Department of Education Scientific Research Project(No.22B0310)。

摘　　要：Since hydrate resources play a part of the stratigraphic framework structure in sediments,establishing a safe and economic method for hydrates exploitation remains the primary challenge to this day.Among the proposed methods,the spontaneous displacement of CH_(4) from hydrate cages by CO_(2) seems to be a perfect mechanism to address gas production and CO_(2) storage,especially in today's strong demand for carbon reduction and replacing clean energy.After extensive lab researches,in the past decade,injecting a mixture of CO_(2) and small molecule gas has become a key means to enhance displacement efficiency and has great potential for application.However,there is a lack of in-depth research on gas flow in the reservoir,while the injected gas always passes through low-saturated hydrate areas with high permeability and then occurs gas channel in a short term,finally resulting in the decreases in gas production efficiency and produced gas quality.Therefore,we explored a new injection-production mode of alternate injection of N2 and CO_(2) in order to fully coordinate the advantages of N_(2) in enhanced hydrate decomposition and CO_(2) in solid storage and heat compensation.These alternate"taking"and"storing"processes perfectly repair the problem of the gas channel,achieving self-regulation effect of CH_(4) recovery and CO_(2) storage.The 3-D experimental results show that compared to the mixed gas injection,CH_(4) recovery is increased by>50%and CO_(2) storage is increased by>70%.Additionally,this alternate injection mode presented a better performance in CH_(4) concentration of produced gas and showed outstanding N_(2) utilization efficiency.Further,we analyzed its self-adaptive gas flow mechanism and proposed an application model of"one injection and multiple production".We look forward to this study accelerating the application of CO_(2)-CH_(4) replacement technology.

关 键 词：HYDRATE Replacement CH_(4)recovery CO_(2)storage Reservoir remediation 

分 类 号：TE377[石油与天然气工程—油气田开发工程]