摘要
在同步压裂过程中，随着地应力条件的改变，裂缝形态也会随之变化。针对这一现象，假设致密储层岩石为均质、各向同性材料，依据断裂力学理论，推导出同步压裂井间裂缝诱导应力计算模型；考虑水力压裂过程中，诱导应力差值对水平应力差异系数的影响，结合复杂裂缝和转向裂缝形成的力学条件，建立同步压裂井间裂缝形态判别模型。计算结果表明：压开裂缝附近水平应力差异系数场呈椭圆形分布，距离压开裂缝越近，水平应力差异系数越小，越易形成复杂或转向裂缝；初始地应力条件对同步压裂井间裂缝形态影响显著，文中压裂条件下，初始水平应力差异系数 0＜Kho≤0.033 时形成转向裂缝， 0.033<Kho<0.361 时形成复杂裂缝，Kho≥0.361 时只能形成单一主裂缝。
Abstract
In the process of synchronous volume fracturing, fracture morphology will change with the change of ground stress condition. In view of this phenomenon, assuming the rock of low permeability reservoirs is homogeneous and isotropic, the calculation model of induced stress of fractures during the process of synchronization fracturing according to theory of fracture mechanics is built. Considering the induced stress difference effect on diversity coefficient of horizontal stress and mechanical formation conditions of complex fracture and turning fracture, the discrimination model of fracture morphology among synchronization fracturing wells is established. The calculation results show that field of diversity coefficient of horizontal stress near the man-made fracture distributes as ellipse, the nearer it is to the fracture, the smaller the diversity coefficient of horizontal stress is, the more easily it is to form complex or turning fracture; the initial stress condition has remarkable effect on fracture morphology. In this paper, when the initial diversity coefficient of horizontal stress is 0<Kho≤0.033, the turning fracture is formed; when the initial diversity coefficient of horizontal stress is 0.033<Kho<0.361, the complex fracture is formed; however, when the initial diversity coefficient of horizontal stress is Kho≥0.361, only a single major fracture is formed.
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