初始水平主应力对应力阴影效应的影响研究

Research on influence of initial horizontal principal stress on stress shadow

介绍应力阴影的概念及其理论模型,结合颗粒流流固耦合计算原理构建模型,模拟并分析单一水力裂缝周围因应力阴影效应产生的诱导应力的分布情况,分析表明应力阴影主要表现为最小水平主应力的增大,且其对水力裂缝压裂效益具有两面性。利用建立的数值模型,进一步分析在不同初始水平主应力下,应力阴影效应对水力裂缝扩展方向的影响,结果表明:初始水平主应力比越大,应力阴影效应产生的诱导压力越大,不利于新裂缝的开裂及发育;当初始裂缝内液压接近或大于最大初始水平主应力时,注水孔压裂水力裂缝的扩展方向将发生转向,有利于复杂裂缝网络的形成。

The concept and theory of stress shadow were introduced. The particle discrete element model-was constructed with the fluid-solid coupling calculation. The distribution of the induced stress due to the stress shadow around a single hydraulic fracture was simulated and analyzed. The analysis shows that the mainly effect of stress shadow is the increasing of the minimum horizontal stress, and the effect has dual character. The effect of initial horizontal stress on hydraulic fracture was analyzed using the established model. The result shows that the induced stress due to the stress shadow was increasing with the increasing of the ratio of the initial horizontal principal stress, and it was more disadvantageous to the dehiscence and development of the new fractures. When the hydraulic pressure in the initial fracture was closed to or greater than the maximum initial horizontal stress, the propagation direction of the hydraulic fracture caused by the infusion holes would be changed, and it was conductive to the formation of a complex fracture network.