Shokir Eissa M, Sallam Samy, Abdelhafiz Mostafa M
Department of Petroleum Engineering, Cairo University, 12613 Giza, Egypt.
Institute for Disposal Research, TU Clausthal, 38678 Clausthal-Zellerfeld, Germany.
ACS Omega. 2024 Dec 18;9(52):51536-51553. doi: 10.1021/acsomega.4c09013. eCollection 2024 Dec 31.
Wellbore stability in extreme drilling environments remains a critical challenge. This study advances the understanding of these complexities through a comprehensive numerical modeling approach. By incorporating thermal, chemical, and hydraulic effects, four refined models were developed to simulate wellbore behavior under high pressures and temperatures. A comparative analysis of four failure criteria and a detailed investigation into the impact of fluid properties on pore pressure and stress distribution provide novel insights. The results indicate that pressure distribution and stress variations around the wellbore are significantly influenced by poroelastic, thermal, and chemical effects. The poroelastic effect increases pressure due to overbalanced drilling conditions, while thermal effects vary with fluid temperature, leading to notable pressure changes. Chemical effects are significant, with lower salinity mud increasing pore pressure and higher salinity decreasing it. Thermal effects primarily dominate stress distribution, altering radial, tangential, and axial stresses, with tangential stresses peaking in the direction of minimum horizontal stress. Collapse area predictions suggest that Mohr-Coulomb and Drucker-Prager criteria predict larger collapse areas compared to Mogi-Coulomb and Modified-Lade criteria, indicating a more conservative approach. Poroelastic effects slightly enlarge collapse areas due to increased pore pressure, while thermal effects reduce collapse areas with cooling and increase them with heating. Higher salinity mud improves formation stability by enhancing effective stress and reducing pore pressure. The results demonstrate that using higher salinity mud enhances formation stability and that careful management of temperature can mitigate stress variations and collapse risks. Regular monitoring and adjustments based on wellbore stability models are essential for optimizing performance and safety in drilling operations. The findings reveal that optimizing mud salinity and carefully managing temperature can effectively enhance formation stability, which offers practical guidelines for mitigating wellbore risks and optimizing drilling operations in challenging formations.
在极端钻井环境下，井筒稳定性仍然是一个关键挑战。本研究通过全面的数值模拟方法，深化了对这些复杂问题的理解。通过纳入热、化学和水力效应，开发了四个精细模型来模拟高压和高温下的井筒行为。对四种破坏准则的对比分析以及对流体性质对孔隙压力和应力分布影响的详细研究提供了新的见解。结果表明，井筒周围的压力分布和应力变化受到孔隙弹性、热和化学效应的显著影响。孔隙弹性效应因过平衡钻井条件而使压力增加，而热效应随流体温度变化，导致明显的压力变化。化学效应显著，低盐度泥浆会增加孔隙压力，高盐度泥浆则会降低孔隙压力。热效应主要主导应力分布，改变径向、切向和轴向应力，切向应力在最小水平应力方向达到峰值。坍塌面积预测表明，与莫吉 - 库仑准则和修正拉德准则相比，莫尔 - 库仑准则和德鲁克 - 普拉格准则预测的坍塌面积更大，这表明采用了更保守的方法。孔隙弹性效应由于孔隙压力增加而略微扩大坍塌面积，而热效应在冷却时减小坍塌面积，在加热时增大坍塌面积。较高盐度的泥浆通过增强有效应力和降低孔隙压力来提高地层稳定性。结果表明，使用较高盐度的泥浆可增强地层稳定性，并且仔细管理温度可减轻应力变化和坍塌风险。基于井筒稳定性模型进行定期监测和调整对于优化钻井作业的性能和安全性至关重要。研究结果表明，优化泥浆盐度和仔细管理温度可有效提高地层稳定性，这为减轻井筒风险和优化复杂地层中的钻井作业提供了实用指南。
