“井工厂”不同压裂模式下裂缝扩展规律数值模拟研究

Numerical simulation of fracture propagation in different fracturing modes of“well factory”

“井工厂”压裂模式可以提高页岩储层体积改造效率和降低施工成本,明确各压裂工艺下诱导应力场的影响因素以及水力裂缝扩展规律对体积压裂缝网预测和工艺优化具有重要意义。为此,利用多孔介质流−固耦合理论和应力叠加原理,建立水平井多裂缝分时扩展力学模型,采用扩展有限元方法,在ABAQUS商业软件上进行二次开发,分析“井工厂”压裂模式下诱导应力影响因素及人工裂缝扩展规律。研究结果表明:改进拉链式压裂产生的诱导应力最大,在保证裂缝转向的同时,可维持裂缝长度和宽度;段间距的增加可有效降低逐次顺序压裂和改进拉链式压裂的诱导应力,并可调整常规拉链式压裂井间应力波动;在改进拉链式压裂模式下,增大井间距可降低后施工水平井各缝受到的缝间应力干扰,但对其他2种工艺的影响不尽相同;井筒两侧诱导应力场的差异程度决定同条裂缝半长的扩展竞争程度,诱导应力小的一侧裂缝优先扩展。

The"well factory"fracturing mode can improve the efficiency of shale reservoir volume stimulation and reduce the construction cost,it is of great significance to clarify the influencing factors of induced stress field and the law of hydraulic fracture propagation in various fracturing processes for the prediction of fracture network under volumetric pressure and process optimization.Based on the theory of fluid-solid coupling in porous media and the principle of stress superposition,a mechanical model of multi-fracture propagation in horizontal wells was established.The extended finite element method was used for secondary development on ABAQUS commercial software to analyze the influencing factors of induced stress and the law of artificial fracture propagation in"well factory"fracturing mode.The results show that the stress interference of the two wells in the conventional zipper fracturing and the improved zipper fracturing mode is obviously stronger than that of the sequential fracturing process.The increase of interval spacing can effectively reduce the induced stress of sequential fracturing and improved zipper fracturing,and adjust the inter well stress fluctuation in the conventional zipper fracturing mode.Increasing the well spacing can reduce the stress interference between fractures in the post construction horizontal well in the improved zipper fracturing mode,but the effects on the other two processes are different.The difference of induced stress field on both sides of the wellbore determines the half−length propagation competition relationship of the same fracture,and the fracture on the side with small induced stress expands preferentially.