川东龙马溪组页岩渗透率各向异性及应力敏感性实验研究

页岩渗透率各向异性和应力敏感性对其水平井产能评价和合理工作制度制定有较大影响,目前还没有对页岩各向异性及其应力敏感性进行过系统的测试分析。基于此,应用川东龙马溪组页岩进行页岩测试渗透率各向异性和应力敏感性研究。实验用岩心分为两组,一组垂直层理面取心,岩心与层理面对称轴的夹角分别为0°、45°、90°,另一组平行层理面取心,岩心与层理面对称轴的夹角分别为30°、90°、150°,利用美国岩心公司的PDP—200脉冲衰减法渗透率仪进行测试。实验结果表明,川东龙马溪组页岩的渗透率均在10~(-6)μm~2数量级,随着与层理面夹角增大,页岩岩心渗透率明显降低,沿层理面取样页岩的渗透率与垂直层理面取样页岩的渗透率比在3左右,在层理面的不同方位取样的页岩渗透率测试结果较为接近;不同岩样的渗透率随着有效应力增大而呈现指数递减,在1 500 psi有效应力时,各岩心渗透率均降低至10~(-9)μm~2数量级的较低水平,平行层理的页岩渗透率应力敏感性相对更强。

Experimental Study on Permeability Anisotropy and Stress Sensibility of Shale of Long Maxi in East Sichuan

Shale permeability anisotropy and stress sensitivity have a great impact on the horizontal well productivity evaluation and rational work system formulation. At present, there is no systematic test analysis of shale anisotropy and its stress sensitivity. Based on this, the shale test permeability anisotropy and stress sensitivity of the LongMaxi Formation shale in the East Sichuan Basin were applied. The cores used in the experiment are divided into two groups. One set of vertical bedding faces is taken, and the angle between the core and the axis of the bedding plane is 0°, 45°, and 90°, and the other group of parallel layers is cored. The angles with the axis of symmetry of the bedding plane were 30°, 90°, and 150°, respectively. The test was tested using the PDP-200 pulse attenuation method of the American Core Company. The experimental results show that the permeability of the LongMaxi Formation shale in the eastern Sichuan Basin is in the order of 10^-6um². With the increase of the angle with the bedding plane, the permeability of the shale core is obviously reduced. The ratio of the permeability of the shale sampled along the bedding plane to the permeability of the shale sampled by the vertical bedding plane is about 3, and the shale permeability test results taken at different orientations of the bedding plane are close; the permeability of different rock samples decreases exponentially with the increase of effective stress. At 1 500 psi effective stress, the permeability of each core is reduced to a lower level of the order of 10^-9um², and the shale permeability stress sensitivity of the parallel bedding is relatively stronger.