Current status and prospects of deep coalbed methane production technology

CAI Wenbin; WANG Jianglong; ZHANG Yanjun; ZHOU Desheng; LEI Xu

doi:10.11799/ce202503001

Abstract：China possesses abundant coalbed methane(CBM)resources,yet their exploitation is hindered by complex geological and engineering conditions.Conventional natural gas well extraction technologies exhibit limited applicability in CBM wells,particularly for deep CBM reservoirs(buried deeper than 1500 m),which exhibit significant differences in extraction characteristics compared to shallow CBM.Through theoretical analysis and field observations,we systematically examined the reservoir characteristics,extraction stages,key controlling factors,and technological advancements for deep CBM development.The key findings include:Firstly,deep CBM reservoirs are characterized by high pressure and temperature,substantial formation energy,thick coal seams,high gas content,and abundant free gas.However,they also exhibit low matrix permeability,poor pore connectivity,high effective stress,and low fracturing fluid recovery rates.Secondly,the primary control factors for extraction and production vary across stages:in the early pressure reduction phase,coal fines significantly impact extraction efficiency;during gas breakthrough to stable production,stress sensitivity becomes critical,necessitating minimized shut-ins to avoid formation damage from discontinuous extraction.Thirdly,a refined five-or-six-stage extraction system is recommended for deep CBM wells to ensure a steady decline in bottomhole pressure,thereby extending the stable production period,which is crucial for maximizing ultimate production capacity.Fourthly,future directions for extraction technology include integrated lifecycle extraction strategies,geology-engineering collaborative approaches,and the application of machine learning and smart extraction systems.This study provides valuable insights and guidance for optimizing extraction and production technologies in deep CBM wells,contributing to the efficient and sustainable development of these resources.