Methane and coal exploitation strategy of highly outburst-prone coal seam configurations

• The strategy combines ground CBM recovery with underground outburst control methods.
• Surface wells pre-drainage are first performed to reduce the burst hazard.
• Surface well pre-drainage creates suitable conditions for underground gas drainage.
• The multiple-seam configurations secure safe and green mining conditions.

Outbursts are the sudden and violent releases of coal and gas from a coalface, resulting in damage to excavations and equipment, loss of life and even disastrous gas explosion if an ignition source is present. The highly outburst-prone coal configurations are formed of outburst-prone coal seams and some of them have high outburst propensity. The direct applications of traditional outburst control methods on these configurations will lead to various problems in mining safety, technical implementation and economy. This article proposes a methane and coal exploitation strategy for highly outburst-prone coal configurations, combining surface coalbed methane (CBM) recovery with underground methane drainage. In this strategy, vertical surface wells are firstly performed to mitigate or eliminate the outburst hazard of the configurations and thereby creates suitable conditions for the following underground protective seam working or methane pre-drainage. Thus the methane of the configuration is exploited, the outburst hazards of the configuration are eliminated and the outburst-prone seams of the configuration are to be mined safely. It is predicted that the methane contents will decrease from 25 m3/t to about 6 m3/t, the outburst hazards will be eliminated completely, and clean and safe mining conditions will be secured by executing this strategy on the Nos. 8, 9 and 10 seams in the Luling mine.