水对含微裂缝页岩渗流能力的影响

页岩储层经水力压裂后,发育不同尺度的裂缝,返排液滞留在储层与裂缝中,改变了页岩储层的含水饱和度,从而影响了页岩气的流动。为研究微裂缝条件下水对页岩储层渗流能力的影响,选取四川盆地下志留统龙马溪组储层黑色页岩,经巴西劈裂造缝处理后开展岩心实验,并结合扫描电镜实验方法以及渗流力学理论对含水条件下页岩储层渗流能力的影响因素进行分析,结果表明:黏土矿物含量以及缝网发育程度决定了页岩储层渗流能力;黏土矿物含量越多,储层渗流能力下降越大;主裂缝的开度及缝网形态控制着水在裂缝系统中的作用范围。通过拟合实验数据建立渗流能力下降幅度与面积密度方程,并对微裂缝条件下水对页岩渗流能力的影响情况做出细致分析。

Effect of water on seepage capacity of shale with microcracks

The shale reservoir develops cracks with different scales after hydraulic fracturing. The flowback fluid stays in the reservoir and the fracture,changing the water saturation of the shale reservoir,thus affecting the flow of shale gas. In order to study the effect of water on the seepage capacity of shale reservoirs under microcrack conditions,the black shale of the Longmaxi Formation reservoir in Sichuan Province was selected and the core experiment was carried out after the crack-making treatment via Brazilian cracking. The influencing factors of shale reservoir seepage capacity under water condition were analyzed by the experimental methods of scanning electron microscopy and the theory of seepage mechanics. The results show that clay mineral content and fracture network development determine seepage capacity of shale reservoirs. The more clay minerals,the greater the decline of reservoir seepage capacity. The opening of the main crack and the distribution pattern of the micro crack control the scope of water in the crack system. The equations of the decreasing extent and area density of seepage capacity were established by fitting experimental data,and the influence of water on shale seepage capacity under micro-crack conditions was analyzed.