A brittleness evaluation method of rock constitutive relationship with Weibull distribution based on double‐body system theory,Energy Science & Engineering

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A brittleness evaluation method of rock constitutive relationship with Weibull distribution based on double‐body system theory
Energy Science & Engineering ( IF 3.5 ) Pub Date : 2020-07-19 , DOI: 10.1002/ese3.708
Hui Zhang _{1,

2} , Zhizhang Wang ₃ , Baotao Ruan ₄ , Zhongcheng Li ₄ , Wanchun Zhao ₅ , Pathegama Gamage Ranjith ₆ , Tingting Wang ₇

Affiliation

Brittleness of rocks plays an important role in the evaluation of unconventional oil and gas reservoir network fracturing and many rock engineering application fields. However, there is still no commonly accepted definition of the concept of brittleness. In this study, the brittleness differences between rocks are understood as the differences of internal microunit strength cracking characteristics under an external load. Because rock ruptures are regarded as a fracturing problem of a double body system, the region where no cracking occurs during the uniaxial compression loading process is regarded as a body I system with elastic deformation characteristics; the region that breaks first and induces the integral fracture of the rock is regarded as a body II system in which the structural strength of the microunit follows the deformation characteristic of the Weibull distribution. An energy quasi‐static equilibrium equation for rock fractures of a double body system under an external load was established. A new index for evaluating brittleness was established based on the energy mutation process of the quasi‐static equilibrium equation of double body system. Sandstone, red sandstone, mudstone, sandy mudstone, shale, limestone, and granite were selected as the research objects, while the correlation curve between the new brittleness index, the Weibull distribution characteristic parameters, and the mutation break point was calculated. The brittleness index studied in this paper reveals the evolution process of integral fractures induced by the internal fractures of rocks, which is important for further understanding the essence of brittleness. These results can provide a new method for further studying the formation process of local fracture networks.

中文翻译：

基于双体系统理论的威布尔分布岩石本构关系脆性评估方法

岩石的脆性在非常规油气藏管网压裂评价和许多岩石工程应用领域中起着重要作用。但是，脆性的概念尚无公认的定义。在这项研究中，岩石之间的脆性差异被理解为外部载荷下内部微单元强度开裂特性的差异。因为岩石破裂被认为是双体系统的破裂问题，所以在单轴压缩载荷过程中没有破裂发生的区域被认为是具有弹性变形特性的I体系统。首先破裂并引起岩石整体破裂的区域被视为主体II系统，其中微单元的结构强度遵循威布尔分布的变形特征。建立了双体系统在外部载荷作用下的岩石裂隙能量准静态平衡方程。基于双体系统准静态平衡方程的能量突变过程，建立了一种新的脆性评价指标。以砂岩，红砂岩，泥岩，砂质泥岩，页岩，石灰岩和花岗岩为研究对象，计算出新脆性指数，威布尔分布特征参数与突变断裂点之间的相关曲线。本文所研究的脆性指数揭示了岩石内部裂缝引起的整体裂缝的演化过程，这对于进一步理解脆性的本质至关重要。这些结果可为进一步研究局部裂缝网络的形成过程提供一种新方法。

更新日期：2020-07-19

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