隔层窜流现象的数值模拟研究

在形成水平裂缝的压裂施工中,常会发生薄层间窜流的现象。借助于有限元分析软件ANSYS,对层间窜流的原因进行了深入的模拟分析。模拟结果表明,在压裂施工中,水平主裂缝附近第二胶结面会发生受拉张开和压裂液渗入的现象,但这并不会直接导致层间窜流,隔层上、下压力差使附近的第二胶结面产生剪切破坏才是层间窜流的直接原因。在此基础上,针对平衡压裂和常规压裂两种工艺,对不同厚度的隔层进行了抗压强度计算,给出两种工艺下隔层不发生窜流的下限厚度,为平衡压裂技术的实施提供了量化的参考标准。

Numerical simulation of interlayer channeling

In the fracturing process for making the horizontal fractures, the interlayer channeling often takes place. In order to investigate the causes of interkyer channeling, the finite element numerical simulations were carried out by means of the software ANSYS. The results demonstrate that the interkyer channeling is resulted from the shear destruction of the second cemented interfaces nearby. The shear destruction is induced by the imbalance of pressures acted on the upper and lower surfaces of interlayer. The lowest limits of interlayer thickness for the balance fracturing technology and the ordinary fracturing technology were determined on a series of calculations. When the thickness of interlayers is over the limits for these two technology,the interlayer channeling would probably take place in the practice. This result may provide a quantitative reference for putting the balance fracturing technique into practice.