Coalbed Methane Industry Development Framework and Its Limiting Factors in China

Table 1

Universal geological reasons for the low production rate of single CBM wells in China.

Reasons	Gas sources	Channels	Driving force	Applicability of development technologies
Characteristics	(1) Methane occurs the adsorption state; (2) The gas saturation is low	(1) Low mechanical strength and high stress sensitivity; (2) Easy to produce coal fines; (3) Tectonically deformed coal is widely distributed where fracture connectivity is poor [25]	(1) Low reservoir pressure; (2) High capillary pressure [26]; (3) High water saturation	(1) In the process of drilling, horizontal wellbores easily collapse; (2) In the process of fracturing, it is difficult to create effective propped fractures; (3) In the process of drainage, it is difficult to ensure the smooth output of CBM
Consequences	(1) The output of CBM wells hardly peaks within a short time; (2) CBM production involves a slow process	(1) Gas migration channels are easily blocked; (2) It is difficult to construct diversion channel in tectonically deformed coal [27]	(1) This factor influences the development cycle of CBM wells; (2) Pressure release within the coal matrix is difficult to obtain [7]	(1) The extraction methods of CBM wells are not fully adapted to the geological conditions of CBM reservoirs; (2) The stimulation effect of development methods is poor [28]