地层压力变化对渗透率的影响实验研究

储层岩石在地下随有效应力改变而发生变形,从而影响其渗流特性。利用从美国引进的三轴向岩石力学测试系统,从岩石的力学特性入手,研究了储层岩石在地层压力下降和压力回弹过程中的变形特征及渗透率变化规律。实验发现,储层岩石的受力变形不是完全弹性的,在地层流体压力回弹过程中,部分变形不可恢复,地层压力恢复时机越晚,产生的塑性变形越大,地层压力恢复后的渗透率保留率越低。对于某些储层岩石,当上覆压力增大,超过其抗压强度后,又会产生裂缝,从而改善其渗透性能。

Experimental Research of Impact of Strata Pressure Change on Permeability

Reservoir rocks deform with the change of underground effective stress,thus influencing their seepage properties.Starting from rock＇s mechanical characters,the author has studied the deformation behaviors of reservoir rocks and the pattern of their permeability variation in the process of pressure drop and pressure rebound by using three axial rock mechanics test system from America.Through experiment,the author has found out that the mechanical deformation is not perfectly elastic,part of which is beyond retrieve in the course of pressure rebound of formation fluid and that the later recovery of strata pressure creates bigger plastic deformation and lower reserved rate of permeability after the recovery of strata pressure.When burden pressure increases to exceed their compression strength,some reservoir rocks will generate fissures to improve their penetrating quality.