Enhancing the safety of coal mining by injecting CO_2 into coalbeds

摘要

Coal mining begins after coalbed methane(CBM) production which reduces CH_4 concentration in coalbeds. However once CH_4 concentration reaches the explosion limit, the threat of explosion accident in the coal mine will be greatly increased. Based on safety production principle, this paper analyses the feasibility of CO_2 injection through CBM wells to control CH_4 concentration and enhance CBM recovery at the same time during CBM production. Safe concentration of CH_4 is determined according to its explosion limit and safety factor. Combined with numerical simulation, a CH_4 concentration control method by CO_2 injection is proposed: firstly the CO_2 injection standard is calculated to ensure CH_4 safe concentration, and then the optimum CO_2 injection rate (14000m~3/d) is determined by comparisons between different injection rates. Finally CO_2 emission reduction and recycle methods are proposed to achieve effective environmental protection and high economic efficiency.