Abstract:
Through the contrast experiments of single component N
2, CO
2 and different ratio of mixture flooding, the displacement laws of coalbed methane under different gas and different proportion are explored. The results show that, with the increase of N
2 displacement pressure, the displacement efficiency increases first and then decreases, the replacing efficiency gets worse, the coal permeability gets lower and lower, but still higher than the original permeability; with the increase of CO
2 displacement pressure, the displacement efficiency increases all the time, the replacing efficiency changes little, the permeability decreases first and then increases, the whole permeability is lower than the original permeability; the laws of mixture (CO
2∶N
2=1∶4) and mixture (CO
2∶N
2=1∶9) are similar to N
2, and the law of mixture (CO
2∶N
2=1∶1) is similar to CO
2. N
2 constant displacement is better than intermittent displacement; CO
2 intermittent displacement is better than constant displacement.