Identifying method of leakage recharge in CBM wells

Drainage and pressure lowering are echnical basis for coalbed methane development, and prompt leakage recharge identification is related to the drainage working system and gas production forecast. Combined with the variation of bottom hole flowing pressure, casing pressure, producing fluid level and gas production of different drainage stages in CBM wells, the existence of leakage recharge is identified by comparison between theoretical and real water production. The paper points out that there is leakage recharge when the real water production is greater than the theoretical value, and the rose fluid level no longer declines after gas production, gas production and casing pressure are maintained at a low level. On this basis, according to the characteristics of dynamic fluid level, casing pressure and gas production, leakage recharge types are classified and the subsequent drainage working system is determined reasonably. The production curves of CBM wells show that this approach is effective in southern Qinshui basin.