清水压裂多场耦合下裂缝扩展规律数值模拟分析

利用室内实验测试研究层段页岩储层的物性参数、岩石力学参数和天然裂缝分布特征参数,建立了清水压裂过程中缺陷性岩体应力场—损伤场—渗流场耦合本构模型和破坏准则。通过Comsol软件进行有限元数值模拟,分析地层分别在拉伸和压剪应力下裂缝的扩展规律,天然裂缝系统开启时,页岩储层水力压裂可以形成人工裂缝网络。当水力裂缝扩展至天然裂缝时,裂缝的宽度有明显的增加,且水力裂缝方向发生改变,沿天然裂缝两翼的其中一翼扩展,另外的一翼并没有扩展。天然裂缝间存在着明显的互相干扰。多裂缝产生的过程是从多个小裂缝向少数大裂缝发展的过程,最终的裂缝条数取决于裂缝之间的连接性;地应力、天然裂缝、射孔井段、射孔方式、地层倾角、施工排量与液体黏度等,是影响多裂缝形成的主要因素。

The Numerical Simulation Analysis of Crack Propagation Law under Riverfrac T reatment M ulti-Field Coupling

Using the indoor experimental test , the intervals shale reservoir physical parameters , the rock mechanics parameters and the natural fracture distribution characteristic parameters were studied ,and the constitutive models of stress field-damage field-seepage field coupling and the failure criteria of the defective rock mass in the process of riverfrac treatment were established . Through the finite element numerical simulation by the software-Comsol , the crack propagation law of formation respectively under tensile and compressive shear stress was analyzed ,when the natural fracture system opens , hydraulic fracturing of shale reservoir artificial fracture network can be formed .When hydraulic fracture extended to natural fracture ,there has been a marked increase the width of cracks ,and hydraulic fracture direction changes ,one of the wings extended along the natural fracture on the wing ,the other one wing does not .There is obvious mutual interference between natural fracture .Process of multi cracks is developed from a small to a large crack fracture ,the final number of cracks depends on the connectivity between the cracks ;stress ,natural fracture ,perforation interval ,perforation ,dip ,construction flow and liquid viscosity ,are the main factors that influence the formation of multi cracks .