热力耦合作用下含瓦斯煤层渗透特性试验研究

Experimental study on permeability properties of coal containing gas with thermo-mechanical coupling

为深入研究含瓦斯煤层渗透率与温度和应力的关系,利用自制三轴渗透仪,进行了不同轴压、围压、孔隙压、温度条件下的渗透率测定试验和煤层微观结构扫描试验,并对试验结果进行了分析.研究结果表明:在热和应力耦合作用下,煤层渗透率主要受煤基质膨胀、煤基质压缩、孔裂隙扩张、孔裂隙闭合、气体吸附、气体解吸等6个因素共同影响;孔隙压力不变,渗透率随有效应力的升高单调递减;轴围压不变,渗透率随孔隙压力的升高呈先减小后平缓再增大的近"U"型变化规律;温度升高,煤基质膨胀致使孔裂隙闭合,煤内气体膨胀致使孔裂隙扩张,两相共同作用,渗透率变化取决于哪一相占优.

In order to further study the relationship between gas permeability and temperature and stress in coal seams, this paper carried out permeability tests under different axial pressure, confining pressure, pore pressure and temperature, and microstructure scanning test of coal seam. The results of the test analysis show that under thermo-mechanical coupling, the permeability of coal containing gas is combined by six main effect factors which are coal matrix expansion, coal matrix compression, pore-cracks expansion, pore-cracks closed, gas adsorption, and gas desorption; while the pore pressure is constant, permeability decreases monotonically with increase of effective stress; while the axial-confining pressure is constant, the variation of permeability just nearly like ＂U＂ shape that reduces after increase and then flat with pore pressure increasing; with temperature increasing, coal matrix swelling resulting pore-cracks closed, coal gas expansion resulting pore-cracks expansion, and when the two phases together, permeability varies depending on which phase dominant.