Characterization of Permeability Changes in Coal of High Rank during the CH₄-CO₂ Replacement Process

Table 4

Calculated results of permeability influenced by coal matrix shrinkage under different confining pressures.

Injection gas balanced pressures (MPa)	Permeability of coal specimens under the influence of coal matrix shrinkage (mD)
	HA coal					HB coal
	6 MPa	8 MPa	10 MPs	12 MPa	14 MPa	8 MPa	12 MPa	16 MPa	20 MPa
6.25	—	0.239	0.134	0.093	0.093	0.267	0.305	0.328	0.228
5.25	0.232	0.252	0.119	0.098	0.098	0.272	0.312	0.321	0.201
4.25	0.261	0.258	0.137	0.140	0.140	0.257	0.286	0.274	0.203
3.25	0.250	0.251	0.118	0.237	0.237	0.285	0.294	0.299	0.219
2.25	0.244	0.242	0.152	0.118	0.118	0.313	0.338	0.312	0.292
1.25	0.393	0.404	0.200	0.178	0.178	0.511	0.494	0.445	0.407