In order to better realize the safe and efficient coordinated development of coal and CBM resources in high gassy mining areas, the four  regions  (planning  region,  preparation  region,  production  region  and  coal  mined-out  region)  linkage  ground-underground   combined drainage mode (new Jincheng mode) and a series of technical systems of CBM in the whole mining area, all stratum layer and all time were innovatively developed. Relying on the “Thirteen Five - Year Plan” national major science and technology projects to continue to tackle key problems, closely combining with the actual production of key coal mining areas in Shanxi Province. This new mode upgraded from the “three regions linkage” three-dimensional extraction mode of CBM developed during the “Eleventh Five-Year” and the “Twelfth Five-Year” Plan and it had been widely used in key coal mining areas of Shanxi Province and achieved good results. The ground pre-drainage technology of CBM in the planning area mainly used vertical wells, directional wells, horizontal wells and other technologies in the early stage. But now it had developed into a well factory intensive development mode and technology dominated by multi-fractured horizontal  well.  After  15  years  of  ground  pre-drainage,  the  average  reduction  of  No.3  coal  seam  in  East  Fifth  Panel  of  Sihe  Mine  of Jinneng Holding Group had reached 55%. The No.5310 and No.5311 working faces in this panel had successfully completed safe and efficient coal mining, realizing low gas mining in high gas content coal seam. The ground-underground combined drainage technology of CBM in the preparation region made full use of the advantages of the greatly increased permeability in the fracturing affected area and the increased production pressure difference of underground open space drainage. Which formed a three-dimensional drainage network, improved the drainage efficiency, effectively alleviated the tension in the replacement of mining, and promoted high production and  efficiency.Based on the characteristics of intense mining activities in the production area and full opening of underground projects, directional drilling rigs were used to accurately complete regional progressive seam drilling, through hole drilling, and high directional long borehole, and accurately and evenly extract the CBM in the production region. This effectively solved the problems of uncontrollable conventional drilling trajectory, easy to form blind areas for drainage, and poor drainage effect, and realized the accurate standard of underground drainage in the production region, ensuring no risk.In view of the problems such as unclear occurrence law of CBM resources in the coal minedout region, difficulty in resource assessment, and lack of safe drilling and mining technology, the calculation method of CBM resources in the coal mined-out region was created. And a series of technologies for ground drilling and mining in coal mined-out region were developed. 129 wells had been demonstrated and promoted in Shanxi key coal mine areas such as Jincheng, Xishan, Yangquan, etc., 128 million cubic meters of CBM had been pumped and utilized, and 1.92 million tons of carbon dioxide had been reduced.The success of the ‘four region linkage’ ground-underground combined drainage mode and a series of technical systems in key coal mining areas of Shanxi had effectively achieved the triple effect of CBM “reducing greenhouse gas emissions, ensuring coal mine safety production, and supplementing green gas energy”. Which provided strong support for China’s CBM production to increase from 2.58 billion cubic meters in 2006 to 19.17 billion cubic meters in 2020. At the same time, it also provided an effective guarantee for the deepening of coal mining depth year by year in key coal mining areas of Shanxi Province, the increasingly complex mine production conditions, the continuous reduction of the number of production mines, and the steady growth of the total coal output.

LI Guofu，ZHANG Suian，JI Changjiang，et al. Mechanism and technical system of ground and underground combined  drainage  of  CBM  in “ four  region  linkage”  in  coal  mining  area[J].  Coal  Science  and  Technology， 2022，50（12）：14−25.