Abstract Refracturing can effectively enhance hydrocarbon production from hydraulically fractured wells. Using self-degradable diverting agents, people can temporarily plug previously generated fractures, and generate a new pair of fractures perpendicular to the direction of the original maximum principle stress (i.e., near-wellbore temporary plugging and diverting technique). To simulate the plugging and diverting process, a numerical model is established using the cohesive zone model (CZM) based on the extended finite element method (XFEM). After this model is verified by the published laboratory testing results, it is applied to understand the influences of stress contrast, formation permeability, rock tensile strength, Young's modulus and injection rate, so as to improve the applicability of temporary plugging and diverting technique under various reservoir conditions. Furthermore, “deflection angle” is proposed to quantitatively analyze the simulation results. This new concept enables the comparison among various cases without the restrictions of fracture length and simulation time. Simulation results indicate that: (1) with increases of stress contrast, rock permeability and Young's modulus, the diverting fractures reorient to the direction of the preferred fracture plane (PFP) more rapidly, which reduces the effectiveness of this technique; (2) propping previously-formed fractures can create higher defection angles of the diverting fractures, which enhances the effectiveness of this technique; (3) enhancing the injection rate can also enhance the effectiveness of this technique, yet there is one optimal injection rate for a given reservoirs. This study provides a systematic guideline for optimizing the temporary plugging and diverting technique under different reservoir conditions.

中文翻译：

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基于 XFEM 的 CZM 重复压裂过程中近井临时堵漏数值模拟

摘要 重复压裂可有效提高水力压裂井的油气产量。利用自降解导流剂，人们可以暂时封堵先前产生的裂缝，并产生垂直于原始最大主应力方向的一对新裂缝（即近井暂堵导流技术）。为模拟堵漏过程，采用基于扩展有限元法（XFEM）的粘性带模型（CZM）建立数值模型。该模型经已发表的实验室测试结果验证后，用于了解应力对比、地层渗透率、岩石抗拉强度、杨氏模量和注入速度的影响，以提高暂堵导流技术在各种油藏条件下的适用性。此外，提出了“偏转角”来定量分析模拟结果。这种新概念可以在不受裂缝长度和模拟时间限制的情况下进行各种情况的比较。模拟结果表明：（1）随着应力对比、岩石渗透率和杨氏模量的增加，转向裂缝更快地重新定向到优选裂缝面（PFP）的方向，降低了该技术的有效性；(2) 支撑已形成的裂缝可以使转向裂缝产生更大的偏转角，提高了该技术的有效性；(3) 提高注射速度也可以提高这种技术的有效性，然而，对于给定的储层，存在一个最佳注入速率。该研究为优化不同储层条件下的暂堵分流技术提供了系统指导。