煤岩渗透率对孔隙压力变化响应规律的试验研究

EXPERIMENTAL RESEARCH ON RESPONSE LAW OF PERMEABILITY OF COAL TO PORE PRESSURE

利用自主研发的含瓦斯煤热流固耦合三轴伺服渗流装置,开展不同有效围压条件下分别充CH4与CO2气体时原煤的渗透率与孔隙压力之间关系的试验研究,以探讨在低孔隙压力的环境下,煤岩渗透率对孔隙压力变化响应的敏感性。研究结果表明:(1)在低孔隙压力的环境下,煤岩渗透率随孔隙压力的增加呈幂函数递减趋势,其过程可分为渗透率加速变化阶段和稳定变化阶段;(2)相同孔隙压力、有效围压条件下,充CH4气体的煤岩渗透率高于充CO2时的煤岩渗透率;(3)采用渗透率变化率Dp以及孔隙压力敏感性系数Cp评价渗透率对孔隙压力的敏感性,得出孔隙压力小于1.0 MPa时,煤岩渗透率对孔隙压力的响应程度较为显著,并基于Cp推导出煤岩渗透率与孔隙压力的函数关系式。

Based on self-developed triaxial servo-controlled seepage equipment for hot-fluid-solid coupling of coal containing methane, permeability of coal sample after injected of CH4 or CO2 under different effective confining pressures and pore pressures is determined, in order to research the response law of the permeability to pore pressure. The results show as follows： （1） At the low pore pressure, the permeability decreases when the pore pressure increases; and its evolution can be divided into accelerating change stage and stable change stage： （2） The permeability of coal when filling CO2 is lower than that when filling CH4 at the same effective confining pressure and pore pressure. （3） Using the parameters, change rate of permeability Dp and the sensitiveness coefficient of pore pressure Cp to evaluate the pore pressure-sensitive, which indicates that the responsiveness of permeability to pore pressure is significant when the pore pressure is less than 1.0 MPa. Then based on the Cp, the functional relationship between permeability of coal and pore pressure is derived.