测量页岩径向渗透率和孔隙度的新方法

为了更加方便准确地获得页岩径向的渗透率,提出了一种测量页岩径向渗透率和孔隙度的压力衰减新方法。该方法通过实验得到氦气沿页岩径向流动时,岩心与PVT容器内壁之间环形空间的压力衰减曲线;据此建立了相应数学 模型,求得了径向模型中压力和时间的半解析解关系式;并通过对实验结果进行拟合,得到了页岩的浓度传导系数和孔隙度;利用浓度传导系数和渗透率的关系,得到了页岩径向方向的渗透率值。利用该方法对2块岩心分别在3组不同的环形空间初始压力下进行了渗透率和孔隙度的测量,并与传统的Dicker和Smits压力衰减方法对比了渗透率测试结果,采用常规的孔隙度测量仪对比了孔隙度测试结果,从而验证该方法的可行性和优越性。该方法相对于传统压力衰减方法除了具有仪器设备更简单、操作更简洁的优势外,还能够同时得到页岩径向渗透率和孔隙度。

A new method to measure radial permeability and porosity of shale

In order to more conveniently and accurately obtain the radial permeability of shale, a new method was proposed to measure the pressure attenuation of radial permeability and porosity of shale. Based on experiments, this method can be used to obtain the pressure attenuation curve in annular space between the core and inner wall of PVT vessel in case of the radial flow of helium along shale. Accordingly, a mathematical model was established to achieve the semi-analytical relation between pressure and time in radial model. Meanwhile, experimental results were fitted to obtain the concentration conductivity and porosity of shale, so as to further derive the radial permeability of shale. This method was adopted to measure the permeability and porosity of two cores under three sets of different initial pressures in annular space. The permeability test results were also compared with those obtained by conventional Dicker and Smits pressure-attenuation methods. The conventional porosimeter was used for comparison in porosity test, thus validating the feasibility and superiority of this method. Compared with conventional pressure-attenuation methods, this model presents the advantages of simple equipment and operation to obtain the radial permeability and porosity of shale simultaneously.