页岩储层应力敏感性及其对产能影响

Stress sensitivity of shale gas reservoir and its influence on productivity

为研究页岩储层应力敏感性及其对产能的影响,选取四川气田下志留统龙马溪组钻井取心样品,开展了应力敏感实验研究,并结合全岩X-射线衍射和高压压汞实验方法,对页岩储层应力敏感的影响因素进行了分析。结果表明,页岩具有强应力敏感特征,有效应力与渗透率变化率呈良好的指数关系,页岩中黏土矿物含量较高,黏土矿物在外力作用下更容易发生应力敏感且不容易恢复。页岩孔隙越小在外力作用下越容易失去渗透能力,应力敏感性越强。通过计算气藏条件下储层的克努森数,确定龙马溪组储层中流动具有多尺度特征。在多尺度流动模型基础上,建立了考虑应力敏感的产能模型,通过实例分析,页岩储层随着生产压差增大产量下降幅度较大。

To study the shale reservoir stress sensitivity and its effect on productivity,four shale samples of Longmaxi Formation of Lower Silurian in southern Sichuan Basin were carried out sensitive experiment.The reservoir porosity was measured using mercury injection capillary pressure.The mineral content of rock was studied through XRD analysis.The experimental results show that,the shale reservoir has the characteristics of strong stress sensitivity,effective stress and permeability change rate showed a good exponential relationship.The high content of clay minerals in shale is important factor for strong stress sensitivity,which will cause the clay minerals to be more easily closed and not easy to recover under the action of external force.Through the Knudsen number calculation under reservoir conditions of reservoir,the Longmaxi reservoir flow with multi scales.Based on multi-scale flow model,the stress sensitive productivity model is established.Through case analysis,shale reservoir production declines sharply with increase production pressure.