Study on influence of wetting modification of medium and high rank coal on gas-water migration

doi:10.16265/j.cnki.issn1003-3033.2025.04.0882

Abstract

Abstract:

In order to solve the problem of increasing difficulty of water injection in deep coal seam and poor inhibition effect of emission, based on the theoretical method of wetting modification of coal seam, wetting agent was used to act on gas-bearing coal body to inhibit gas desorption and migration. The fluorocarbon FS-3100 surfactant with strong wettability was used to test the influence of wettability on the gas-water migration process in coal through gas-containing coal desorption test and fracturing fluid displacement flow test, and to explore the change mechanism of coal wettability on gas-containing coal desorption efficiency and flow capacity. The results show that the surface tension of water is reduced to 17.9 mN /m after adding wetting agent in water, and the contact angle of coal water is only 3-3.5°. After the wetting agent was used to modify the coal body, the desorption rate of gas in the coal is significantly reduced. The gas desorption rates of Xinjing and Baode coals are reduced to 46.08% and 39.2%, respectively, which are 8.4% and 9.8% higher than that of water. After the wetting agent acts on the coal body, the displacement flow rate of the Xinjing coal sample increases from 8.59% to 14.10%, and the Baode coal sample increases from 10.65% to 16.67%, and the water injection capacity of the coal body is significantly enhanced. The wetting agent molecules are adsorbed on the surface of the coal matrix, which reduces the interfacial tension between coal and water and the surface energy of the coal body, so that the friction resistance of the water molecules flowing in the pores and fissures of the coal body is reduced, and the water molecules can infiltrate smaller-scale pores and produce stronger water lock effect. Finally, the gas desorption and migration adsorbed on the pores and coal surface are inhibited, and the gas plugging effect is formed.

Key words: medium-high rank coal, wetting modification, gas-water migration, surfactant, gas desorption

CLC Number:

X936

QI Yufei, TIAN Lin, CAO Yunxing. Study on influence of wetting modification of medium and high rank coal on gas-water migration[J]. China Safety Science Journal, 2025, 35(4): 127-136.

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活性剂质量分数/%	0.001	0.005	0.01	0.03	0.05	0.1	0.3	0.5
FS-3100/(mN·m^-1)	38.3	27.7	20.1	18.0	17.8	17.9	17.8	17.8
清水/(mN·m^-1)	71.8

压裂液类型	质量分数/%	黏度/ (mPa·s^-1)	酸碱度/ pH	表面张力/ (mN·m^-1)	新景煤样接触角/(°)	保德煤样接触角/(°)
FS-3100	0.05	1	6	17.8	3.5	3
清水	0	1	7	71.8	73.4	67.1

煤样编号	压裂液类型	压裂液接触角/ (°)	干燥煤样质量/g	平衡压力/ MPa	样品吸附量/ (cm³·g^-1)	样品解吸压力/ MPa	样品解吸量/ (cm³·g^-1)	解吸率/%
XJ-1	清水	73.4	256.48	2.08	8.011 2	1.31	4.029 5	50.30
XJ-2	0.05% FS-3100	3.5	256.80	2.08	8.027 2	0.82	3.699 3	46.08
BD-1	清水	67.1	227.55	2.16	6.102 43	1.54	2.651 8	43.45
BD-2	0.05% FS-3100	3	227.54	2.16	6.109 82	1.04	2.394 9	39.20

采样矿井	煤样编号	压裂液类型	液体表面张力/ (mN·m^-1)	105 ℃真空干燥后样品质量/g	高压饱和压裂液质量/g	煤样含水饱和度/%	驱替后样品质量/g	压裂液驱替占比/%
新景	XJ-1	清水	71.8	198.73	201.99	1.640	201.71	8.589
新景	XJ-2	0.05% FS-3100	17.8	140.70	142.90	1.564	142.59	14.091
保德	BD-1	清水	71.8	133.15	137.00	2.891	136.59	10.649
保德	BD-2	0.05% FS-3100	17.8	199.89	204.75	2.431	203.94	16.667

压裂液类型	表面张力/ (mN·m^-1)	新景煤接触角/ (°)	保德煤接触角/ (°)	12 MPa 侵入新景煤孔隙直径/nm	12 MPa 侵入保德煤孔隙直径/nm
清水	71.8	73.4	67.1	6.84	9.31
0.05% FS-3100	17.8	3.5	3	5.92	5.93