基于多尺度均匀化理论的页岩强度表征

页岩强度是页岩油气开发所必需的基础技术参数，目前宏观室内实验和测井解释在制样、参数连续解释等方面存在困难。为实现页岩多尺度强度的有效评价，基于最大塑性耗散能原理，并结合微观多孔介质理论建立了页岩微/细观强度均匀化Π函数模型。根据页岩微观力学测试评价了纯黏土矿物的基本力学属性，开展了页岩微/细观力学测试的数值模拟，并通过量纲分析求解页岩微/细观硬度-强度模型。结果表明，微观尺度下的黏土堆积密度对强度参数影响显著，细观尺度下受非黏土夹杂相的影响，硬度和内聚系数的比值与摩擦系数正相关。开展了页岩细观力学实验，根据模型求解结果开展页岩宏观强度预测。以常规实验结果作为约定真值进行归一化比对分析的结果显示，页岩内摩擦角的归一化均值为1.12，内聚力的归一化均值为1.21。页岩强度表征新体系为有效解决页岩油气开发提供了依据。

Shale strength characterization based on the multi-scale homogenization theory

Shale strength is a basic technical parameter required for shale oil and gas development. At present, macroscopic laboratory test and logging interpretation have problems with sample preparation and discontinuous interpretation of parameters. To effectively evaluate shale multi-scale strength, the micro/meso-strength homogenization Π function models of shale were established based on the principle of maximum plastic dissipation energy and the theory of microscopic porous media. The basic mechanical properties of pure clay minerals were evaluated by shale micromechanical test. Meanwhile, the numerical simulation of shale micro/meso-mechanical test was performed. Micro/meso scale hardness-strength model was solved by dimensional analysis. The results demonstrate that the clay packing density has a significant influence on strength at a micro scale. Under the influence of non-clay inclusions, the ratio of hardness and internal cohesion coefficient is positively correlated to friction coefficient at a meso scale. According to the shale meso-mechanical test, the prediction of shale macro strength parameters was performed based on model solutions. The normalized comparison analysis was conducted considering the common lab results as conventional true value. The results show that the normalized mean value of the friction angle is 1.12, and that of the cohesion is 1.21.The established system on shale strength characterization can provide basis for effectively solving oil and gas development.