Wellbore instability has become an increasing concern for horizontal wells, especially with the move towards using drilling innovations that the entire lateral sections are remained without casing during the lifetime of the reservoir and after plug and abandonment operations. We aim to understand the long-term effect of viscous deformation on wellbore stability for horizontal wells through advanced laboratory experiments and viscoplastic simulations. Two-stage single lateral hole tests were conducted on chalk samples, where a horizontal wellbore was drilled laterally at the center of a cylindrical specimen and loaded under triaxial condition with a constant stress ratio. The chalk samples were imaged at two stages in the creep phase using X-ray computed tomography CT(scanning) to precisely observe the breakout development of the damaged zones formed around the borehole. The results from the experiments and CT analysis confirmed model predictions. Results presented in this work clearly demonstrate that viscous deformation can trigger failure modes and induce breakout development around the wellbore in the creep phase.

井筒不稳定性已成为水平井日益受到关注的问题，特别是随着向使用钻井创新的发展，即在油藏寿命期间以及在堵塞和废弃操作之后，整个侧向部分都保持无套管。我们的目标是通过先进的实验室实验和粘塑性模拟来了解粘性变形对水平井井筒稳定性的长期影响。对白垩样品进行了两阶段单侧孔试验，其中水平井筒在圆柱形样品的中心横向钻孔并在恒定应力比的三轴条件下加载。使用 X 射线计算机断层扫描 CT（扫描）在蠕变阶段的两个阶段对白垩样品进行成像，以精确观察钻孔周围形成的损坏区域的爆发发展。实验结果和 CT 分析证实了模型的预测。这项工作中提出的结果清楚地表明，粘性变形可以触发失效模式并在蠕变阶段引起井眼周围的突破发展。