Mechanism of Increasing the Permeability of Water-Bearing Coal Rock by Microwave Steam Explosion

Table 1

NMR test parameter setting table.

RF signal frequency main value SF	RF signal frequency offset	RF 90°pulse width
23 MHz	404.68 kHz	11.52 μs
RF 180° pulse width	Digital gain DRG1	Analog gain RG1
23.52 μs	3	20
Accumulated sampling times NS	Echo interval TE	Corresponding pressure of 50 mm coal rock sample
16	0.15 ms	3.86 MPa
Coal core length	Centrifugal speed	Corresponding centrifugal force of 50 mm coal rock sample
50 mm	8000/min	560 psi
Radio frequency delay RFD	Repeat sampling, interval time TW	Sampling frequency of the signal received by the receiver
0.02 ms	2500 ms	250 kHz
Surface tension at the air/water interface	Wetting angle at gas-water centrifugation	Centrifugal force corresponding to pore radius
72 mN/m	0°	37 nm