致密砂岩多段分簇压裂中孔隙压力场对多裂缝扩展的影响

发布时间：2018-09-16 20:35

【摘要】：为了研究致密砂岩多段分簇压裂中孔隙压力场对多裂缝扩展的影响,采用300 mm×300 mm×600 mm天然砂岩进行真三轴水力压裂实验,实验过程中采用2套压裂液注入系统分别独立控制2条水力裂缝,实验后将试件连续切片分析实验结果,同时采用三维流固耦合数值模拟方法研究孔隙压力场对水力裂缝扩展的影响。结果表明:在致密砂岩压裂中,由于孔隙压力场的存在,无论是簇内裂缝还是簇间裂缝扩展,当缝间距与裂缝半长的比值较小时,裂缝之间表现为相互吸引;当缝间距与裂缝半长的比值较大时,裂缝之间的相互影响较弱,多裂缝之间未出现相互排斥现象;除缝内净压力、缝间距、应力差外,裂缝周围孔隙压力场也是影响多裂缝扩展的重要因素;孔隙压力的增大减小了有效应力,岩石更容易发生剪切破坏,从而加速了裂缝的非平面、非对称双翼扩展;现场致密砂岩多段分簇压裂应增大簇间和簇内射孔间距,可避免压裂液滤失导致裂缝长度的减小,增大储层的改造体积。
[Abstract]:In order to study the effect of pore pressure field on the propagation of multiple fractures in dense sandstone multistage fracturing, the true triaxial hydraulic fracturing experiment was carried out with 300 mm 脳 300 mm 脳 600 mm natural sandstone. During the experiment, two fracturing fluid injection systems were used to control two hydraulic fractures independently. After the experiment, the samples were sliced continuously to analyze the experimental results. At the same time, the effect of pore pressure field on hydraulic fracture propagation is studied by using three dimensional fluid-solid coupling numerical simulation method. The results show that in tight sandstone fracturing, due to the existence of pore pressure field, the fractures attract each other when the ratio of fracture spacing to fracture half length is small. When the ratio of fracture spacing to half length is larger, the interaction between fractures is weak, and there is no mutual repulsion between multiple fractures, except for net pressure, spacing and stress difference. The pore pressure field around the fracture is also an important factor affecting the propagation of multiple fractures, the increase of pore pressure reduces the effective stress, the rock is more prone to shear failure, which accelerates the non-plane and asymmetric biplane propagation of the fracture. Cluster fracturing of tight sandstone in situ should increase the spacing between clusters and injector holes to avoid fracturing fluid filtration resulting in the decrease of fracture length and increase the volume of reservoir reconstruction.
【作者单位】：中国石油大学石油工程学院;
【基金】：国家自然科学基金优秀青年科学基金项目(No.51322404)资助
【分类号】：TE357.1

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