Abstract Wellbore strengthening (WBS) treatment uses lost circulation materials (LCMs) to seal fractures emanated from a wellbore to enhance the pressure-bearing capability of a fractured rock formation during drilling a well. The plugging zone made of LCMs to prevent high wellbore pressure from being completely transferred to fracture tip is permeable and movable. The mechanical responses of wellbore-fracture-plug systems are thus important to WBS designs. A fully coupled hydraulic fracture model is presented to simulate the evolution of near-wellbore stress, fracture opening and internal pressure for finding the way of mitigating the risk of plug failure. Laboratory results were first reported on the ranges of plug permeability and strength in producing plug failure. A symmetric bi-wing fracture geometry is employed in the model, and the roles of in situ stresses, and plug location, dimension and permeability are studied in terms of dimensionless parameters. The numerical results show that in addition to increasing hoop stress, the less permeable plug can slow pressure enhancement rate at its downstream to postpone tensile plug failure caused by increasing fracture opening. The strengthening duration prolongs in rocks under an isotropic in situ stress condition, by plugging fractures at or near their fracture mouth, moderately increasing plug length and width, and decreasing plug permeability. Not only do the time-varying results recover most of the findings obtained by the fixed pressure fracture model, but they are more suitable to the plug failure analysis because the unbalanced pressure on both sides of the permeable plug, controlling shear plug failure, varies transiently.

中文翻译：

---

渗透塞对井筒加固的影响

摘要 井筒加固 (WBS) 处理使用堵漏材料 (LCM) 密封井筒中的裂缝，以提高钻井过程中裂缝岩层的承压能力。由 LCM 制成的封堵层可防止高井筒压力完全转移到裂缝尖端，具有渗透性和可移动性。因此，井眼-裂缝-塞系统的机械响应对 WBS 设计很重要。提出了一个完全耦合的水力压裂模型来模拟近井眼应力、裂缝开口和内压的演变，以寻找降低塞子失效风险的方法。实验室结果首先报告了导致堵塞破坏的堵塞渗透率和强度范围。模型中采用对称双翼断裂几何，并根据无量纲参数研究了地应力、塞位置、尺寸和渗透率的作用。数值结果表明，除了增加环向应力外，渗透性较低的塞子还可以减缓其下游的压力增强速率，从而推迟因裂缝开口增加而导致的拉伸塞子失效。岩石在各向同性地应力条件下，通过在其裂口处或附近封堵裂缝，适度增加塞长和宽度，降低塞渗透率，强化持续时间延长。时变结果不仅恢复了固定压力裂缝模型得到的大部分发现，而且由于渗透塞两侧的压力不平衡，控制了剪切塞破坏，因此它们更适合塞破坏分析，