径向井排引导水力压裂裂缝扩展机理研究

为探究径向井排系统对裂缝的影响，明确水力裂缝的扩展规律，利用扩展有限元理论建立了流固耦合三维裂缝扩展模型，模拟了受径向井排引导的水力裂缝扩展过程。重点分析了3种影响因素（径向井排方位角、水平地应力差、径向井孔径）对水力裂缝的引导机理。首次提出了"引导因子"的概念，并将其作为有效评价径向井排引导效果的量化参数。研究发现，径向井方位角、水平地应力差、径向井井径会对水力裂缝的引导效果产生影响：较小的径向井方位角、水平地应力差以及较大的井径都使径向井排具有较强的引导能力和较好的引导效果，反之亦然。同时，较大井径对增加水力裂缝宽度有明显作用。最后，利用大尺寸真三轴水力压裂模拟试验证实了数值模拟结果具有一定的准确性。

Effect of Radial Well Guidance on Hydraulic Fracturing Crack Propagation Mechanism

To study the effect of radial well guidance on cracks and understand the pattern of hydraulic fracturing crack propagation, a fluid-solid coupled three-dimensional crack propagation model is constructed based on the extended finite element theory and further used to simulate the hydraulic crack propagation process induced by radial well guidance. In particular, the effect of three factors (radial well azimuthal angle, horizontal stress difference, and radial well radius) on the guidance of hydraulic crack propagation are discussed. The concept of a "guidance factor" is first proposed in this study and used as a quantitative parameter for evaluating the guiding performance of the radial well. The results revealed that the guiding performance in hydraulic crack propagation can be affected by all three factors, including radial well azimuthal angle, horizontal stress difference, and radial well radius. Specifically, a smaller radial well azimuthal angle, a larger horizontal stress difference, and a larger radius for the radial well can enable a strong guiding ability for the radial well and therefore realize a decent guiding performance, and vice versa. Finally, the accuracy of the numerical simulation results is validated by large-scale true triaxial hydraulic fracturing simulation tests.