Research status and prospect of gas extraction in abandoned/closed coal mines in China

HUA Xinzhu; QIN Hao; HAO Dingyi; SHI Biming; LIN Baiquan; ZHAO Zhigen; ZHANG Miao

doi:10.12438/cst.2024-1511

Abstract：Driven by the"Carbon Peaking and Carbon Neutrality"goals,the energy structure has ushered in high-quality development in China.Up to now,1 billion tons of backward coal production capacity has been eliminated,and the number of abandoned/closed coal mines has increased rapidly.According to the research,it is estimated that by 2030,there will be 15 000 abandoned/closed mines in China,of which nearly 500 billion m3 of unconventional natural gas will be stored.In order to build a clean,low-carbon,safe and efficient energy system and accelerate the development of new productivity,it is urgent to increase the extraction and development of residual gas in aban-doned/closed coal mines in China.The research progress and existing problems of gas ground extraction theory,technology and process equipment in abandoned coal mines in China are systematically introduced and analyzed,and the key directions and potential hotspots of future research are put forward.Firstly,the gas occurrence law of abandoned/closed coal mines is summarized,the evaluation methods of remaining gas resources are summarized and compared,and the gas seepage and migration law in the process of surface extraction of aban-doned coal mines is analyzed.Secondly,two common ground gas extraction technologies for abandoned/closed coal mines and the adop-ted drilling extraction process equipment are summarized,and the similarities and differences with the production mine surface drilling gas extraction process are compared and analyzed.Thirdly,the deficiencies in the research are analyzed from the aspects of gas drainage the-ory,technology and process equipment in abandoned/closed coal mines:①The inhabitation space and mechanism of gas resources are un-known.②The evaluation of gas resources is imprecise.③The law of gas secondary migration and dynamic accumulation is unclear.④The research on seepage and migration law of gas extraction is insufficient.⑤The key technology of gas extraction is immature.⑥The ground drilling process equipment is incomprehensive.⑦The gas extraction system is imperfect.Finally,the future research direction is put forward concisely:Revealing the occurrence characteristics and migration mechanism of residual gas resources under different influen-cing factors,constructing the theoretical model of accurate prediction of gas reserves and resources in abandoned coal mines,expounding the distribution characteristics and evolution process of secondary migration and accumulation range of residual gas,enriching and perfect-ing the research theory of residual gas seepage and migration law in the process of surface extraction,gradually optimize the technical sys-tem of surface gas extraction in abandoned/coal mines,systematically upgrade the surface drilling process equipment of abandoned/coal mines,gradually realize the intelligent surface drilling process of abandoned/coal mines,and further improve the surface gas extraction process equipment of abandoned/coal mines.Research on the accurate and safe development of abandoned/closed coal mine gas resources is of great significance for improving the safety level of abandoned/closed coal mines,promoting energy structure adjustment,ensuring na-tional energy security and promoting sustained and healthy economic development.