The problem of creating unwanted fractures while drilling ultradeep wells is mitigated with the application of wellbore strengthening techniques. Despite the numerous applications, an open question remains about the efficiency of the loss of circulation materials (LCM) and its implications on the closure stress distribution change during plugging. This work investigates the effects on the stress field before and after plugging along the fracture extension axis by introducing a hydrodynamic plug. With the hydrodynamic plug, fluid flow is constrained by pressure conditions at specific locations in the fracture simulating the LCM. Three different scenarios were considered. First, the efficiency of the bridge is simulated by varying the pressure drop. Second, the location of the bridge inside the fracture and finally a nearly packed fracture. The models are fully coupled and were solved with the finite element method in impermeable and permeable hard rocks. We find that for high-efficiency bridges, narrower fracture profiles are predicted, which causes the induced closure stresses to increase significantly. On the other hand, when the bridge is close and near the wellbore area, the fracture profiles are maintained wide and narrow when it is nearest to the tip. The predicted fracture geometry induces higher closure stresses when the plug is near the well and slightly reduces when it is near the tip. Finally, the pressure profile resulting from the packed fracture significantly affects the fracture dimensions, resulting in narrower fracture, however resulting in a smooth variation of induced closure stresses with high magnitude comparable to the stresses at the state of propagation. The diffusion occurring in the permeable case creates back-stresses that appear to have an additive contribution to the induced closure stresses. This underlines the significance of diffusion on the induced coupled closure stresses for large fractures while performing wellbore strengthening methodologies.

中文翻译：

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井筒加固问题中闭合应力分析的水动力模型

通过应用井筒加固技术，在钻超深井时产生不需要的裂缝的问题得到缓解。尽管有许多应用，但关于循环材料损失 (LCM) 的效率及其对封堵过程中闭合应力分布变化的影响仍然存在一个悬而未决的问题。这项工作通过引入流体动力塞，研究了沿裂缝延伸轴封堵前后对应力场的影响。使用流体动力塞，流体流动受到模拟 LCM 的裂缝中特定位置的压力条件的限制。考虑了三种不同的情况。首先，通过改变压降来模拟电桥的效率。其次，桥梁在裂缝内的位置，最后是几乎挤满的裂缝。这些模型是完全耦合的，并在不透水和透水硬岩中用有限元法求解。我们发现，对于高效桥梁，预测的裂缝剖面会更窄，这会导致诱导闭合应力显着增加。另一方面，当桥梁靠近井筒区域时，裂缝剖面在最靠近尖端时保持宽窄。当塞靠近井时，预测的裂缝几何形状会引起较高的闭合应力，而在靠近尖端时会略微减小。最后，填充裂缝产生的压力分布会显着影响裂缝尺寸，导致裂缝变窄，但会导致诱导闭合应力的平滑变化，其幅度与传播状态下的应力相当。在可渗透情况下发生的扩散会产生似乎对诱导闭合应力具有附加贡献的背应力。这强调了在执行井筒加固方法时扩散对大裂缝的诱导耦合闭合应力的重要性。