水平井多裂纹同步扩展的偏折分析

水平井压裂技术是近几年油气工业发展起来的新技术，用于提高油气井的产量。然而在裂纹扩展的过程中，裂尖决定了裂纹的起裂与扩展方向，这会直接影响储层的压裂效果，所以人们对于这项技术还需要更进一步的认识。根据裂尖的应力场特性建立了裂尖权函数，能较准确地描述裂尖的应力状态，判断裂纹的扩展方向。在利用网格重剖分方法并结合最大主应力准则对水平井多裂纹扩展进行分析的基础上，通过裂尖权函数方法分析了水压裂纹在应力差、裂纹数目和裂纹间距等条件下产生偏折的原因。最终结果表明，裂纹在开裂时裂尖处x与y方向的等效应力变化不明显，裂纹的偏折主要与裂尖xy方向的等效应力有关。 

Deflection of multi-crack synchronous propagation in horizontal well

Horizontal well fracturing, a popular new technology developed in oil and gas industry, is utilized to enhance the production of wells. However, crack tips determine the crack initiation and propagation direction in the process of fracture growth and have a significant effect on the fracturing results. In this sense, in-depth understanding is required for this technology. In this paper, weight function at the crack tip is built according to the characteristics of stress field at the tip. The function can accurately describe the stress state at the crack tip and determine the growth direction. Based on the analysis of multi-crack propagation in the horizontal well, which is simulated by mesh regeneration method together with maximum principal stress principle, weight function at the crack tip is used to explain the reason of crack deflection under the conditions of stress contrast, crack number and distance among cracks. The final results indicate that the equivalent stresses in x and y direction at the crack tip have no distinct change and the deflections are mainly related to the equivalent stresses in xy direction.