Experimental investigation on enhancing coalbed methane recovery by injecting high temperature CO2

The high metamorphic grade and low bedding development of coal,along with the low reservoir pressure of gas have seriously restricted the development and usage of coalbed methane. In order to promote the fundamental re- search on enhanced coal bed methane recovery,a series of laboratory experiments were conducted on raw coal speci- mens by using special equipment,which is designed and developed independently,to investigate the effect of different injecting pressure and temperature of CO2 The results show that,the pressure and temperature of injected CO2 are the main factors which have impact on output rate of CH4 and CO2 storage,higher injection pressure and temperature can lead to more CH4 output and CO2 storage and more rapider rate of CH4 output and CO2 storage,the increase of CO2 pressure,from 2 MPa to 4 MPa,can result in the increase of CH4 output rate,from 6. 7% to 17. 4% ,and CO2 storage (78. 6% -99. 7% );the increase of injecting temperature (28 ℃ to 60 ℃ ) can lead to the increase of CH4 output rate (40. 0% -43. 8% ) and CO2 storage (23． 8% -38． 4% ),but reduce the replacement ratio,which is from 8. 4% to 20.2% . The increase of injection pressure and temperature can cause greater deformation of coal samples,the axial strain can increase by 98. 1% and 104. 7% . The permeability of coal decreases about 37. 1% -71. 3% after room tempera- ture displacement experiment but the reduction become less when the injection temperature increases,which become 19. 8% -64. 3% .