声震法提高煤储层渗透率的实验与机理

Experiment and mechanism for enhancing coalbed penetrating coefficient with ultrasonic vibration

为了提高低渗透煤层的渗透率,采用自制的可控声震法煤层气渗流实验系统,实验研究了不加声场和加声场作用下煤样的渗透特性。实验研究得出:当轴向应力和孔隙压力一定时,随围压的增大煤样的渗透率减小;当围压和孔隙压力一定时,在煤样应力应变曲线的初始压密和弹性阶段,渗透率随轴向应力增大而减小。在应变硬化阶段,因试件体积膨胀渗透率随轴向应力增大而增大;在相同轴向应力、围压、孔隙压力条件下,声场作用能提高煤样的渗透率,且渗透率随作用时间的增长而增加。研究结果表明:渗透率与平均有效应力呈负指数关系,声震法提高煤储层渗透率的机理主要源于声波的机械振动和热效应,研究成果为低渗透煤层提高煤层气抽采率探索出一条新的技术和方法。

With the self-explored coal gas penetrating experimental system of controllable ultrasonic vibration.The experiment studies coal sample’s seepage characteristics with and without the effect of sound field.The experiment shows: When axial stress and pore pressure keep unchanging,the coefficient of coal’s penetration reduces with the increasing of confining pressure.When axial stress and pore pressure keep unchanging,the coefficient of coal’s penetration reduces as well with the increasing of axial stress in the initial densification and elastic stage of coal sample’s stress and strain curve.In the phase of strain and densification penetrating rate goes up with the increasing of axial stress.Under the same axial stress,confining stress and barometric pressure,the sound field effect can enhance coal’s e penetrating coefficient that also increases along with the growth of time.The findings indicate: The penetrating coefficient makes a negative exponent relation with average effective stress.The mechanism of ultrasonic vibration enhancing penetrating coefficient in coal bed mainly stems from mechanical vibration and thermal effect.The research results find out new technology and method for enhancing gasdrawing rate in low penetrating coefficient coal beds.