Study and application of acid pickling technology in well bore for coal-bed methane wells

A large amount of coal slime could be produced during CBM wells drainage process,could cause pump leakage,stuck pump or sieve tube blockage,and lead to drainage work interruption,coal seam permeability damage and gas production decrease. In order to deal with this severe problem,the acid pickling technology has been developed based on slime component analysis,acid formula study,and process design to solve the problems like stuck and blockage down in the well bore. To apply this technology,acid fluid is injected into casing tubing annulus and is then discharged through oil tube. By doing so,slime jam could be removed,the duration of production could be maximized,and workover job could be avoided remarkably without interrupting drainage process. Field application shows a good application potential with a 90. 5% efficiency,which illustrates a good prospect of application.