矿物界面刚度对页岩水力压裂裂缝扩展规律的影响研究

doi:10.13809/j.cnki.cn32-1825/te.2023.01.011

摘要/Abstract

摘要：

为了探究矿物界面作用对页岩水力压裂裂缝起裂和扩展的影响，建立了页岩微观结构模型，并将零厚度cohesive单元嵌入实体单元内，运用数值模拟方法研究矿物边界界面刚度对水力裂缝扩展的影响，得到矿物界面作用影响下页岩水力压裂裂缝扩展规律。结果表明，页岩水力压裂裂缝破坏形式以拉伸破坏为主，裂缝扩展路径包括两种方式：一是沿着矿物边界扩展，二是穿过矿物边界进入矿物内部扩展。随着矿物边界界面刚度的增大，裂缝起裂压力和孔隙压力逐渐增大，裂缝长度、数目和面积逐渐减小，裂缝宽度逐渐增大，容易形成短而宽的裂缝。页岩储层开展水力压裂作业应该优先选择矿物边界界面刚度较小的位置。研究成果有助于揭示矿物界面作用对页岩水力裂缝扩展的作用机理，为合理选择页岩气储层水力压裂作业层位提供理论依据。

关键词: 页岩, 水力压裂, 裂缝扩展, 零厚度cohesive单元, 界面刚度, 数值模拟

Abstract:

In order to study the influence of mineral interface action on the initiation and propagation of shale hydraulic fracturing fractures, a shale microstructure model was established. In the model, the zero-thickness cohesive element was embedded in the solid element. A numerical simulation of the effect of mineral boundary interface stiffness on hydraulic fracture propagation was carried out to reveal the law of shale hydraulic fracturing crack propagation under the influence of mineral interface action. The results show that the tensile destruction is the main form of fracture failure of shale hydraulic fracturing. The crack propagation path consists of two ways, one is to extend along the mineral boundary, and the other is to cross the mineral boundary and enter the mineral to expand. With the increase of the mineral boundary interface stiffness, the crack initiation pressure and pore pressure gradually increase, the length, number and area of the cracks gradually decrease, and the width of the cracks gradually increases, so that it is easy to form short and wide cracks. When carrying out shale hydraulic fracturing operations, the location where the stiffness of the mineral boundary interface is lower should be selected first. The research results help to reveal the action mechanism of the mineral interface action on the expansion of the shale hydraulic fracture, and provide a theoretical basis for the reasonable selection of the hydraulic fracturing layer position of the shale gas reservoir.

Key words: shale, hydraulic fracturing, crack propagation, zero thickness cohesive element, interface stiffness, numerical simulation

中图分类号:

TE377

候梦如,梁冰,孙维吉等. 矿物界面刚度对页岩水力压裂裂缝扩展规律的影响研究[J]. 油气藏评价与开发, 2023, 13(1): 100-107.

Mengru HOU,Bing LIANG,Weiji SUN, et al. Influence of mineral interface stiffness on fracture propagation law of shale hydraulic fracturing[J]. Reservoir Evaluation and Development, 2023, 13(1): 100-107.

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矿物	弹性模量（GPa）	泊松比
石英	95.89	0.07
黏土	14.68	0.30
方解石	79.23	0.31
长石	69.05	0.36
黄铁矿	306.17	0.14