页岩气藏应力敏感效应实验研究

Experimental study on stress sensitivity of shale gas reservoirs

页岩气藏降压开采过程中,地层压力和井底压力的变化导致气藏产生应力敏感效应,使气藏流体的流动动态和气藏产能受到影响。为了明确开采压力的下降对气藏渗透率变化的影响,实验通过改变内压与围压这2种方式,对页岩气藏的应力敏感效应进行了研究。研究结果表明:页岩的渗透率随着内压的降低而下降,随着上覆岩层压力的增加而下降;页岩渗透率与内压的变化存在明显的指数关系;页岩对外压的敏感效应远远大于对内压的敏感效应。该研究对确定页岩气藏产能及制订气井合理生产制度具有一定意义。

The change of formation pressure and bottomhole pressure leads to stress sensitivity during the blowdown recovery of shale gas reservoirs,affecting the flow performance and productivity.To study the effects of pressure decrease on the permeability changes of gas reservoirs during recovery,experiments were conducted to study the change of internal pressure and overburden pressure on the stress sensitivity of shale gas reservoirs.Study results indicated that shale permeability decreased with the drop of internal pressure and the increase of the overburden pressure.The permeability of shale was in obvious exponential relationship with the change of internal pressure.The sensitivity of shale to overburden pressure was far greater than that to internal pressure.The study is of some significance to determining the productivity of shale gas reservoirs and reasonable production systems for gas wells.