Coupled Hydromechanical Analysis Model for the Effect of Drilling Mud Weight on the Wellbore stability with Anisotropic Stress Regime

Wellbore stability can impose significant costs on drilling operations, but the application of comprehensive geomechanical models can substantially mitigate these expenses. Uncontrollable parameters such as in-situ stresses, formation strength, drilling trajectory, pore pressure, and drilling fluid pressure play a crucial role in the occurrence of wellbore instability. However, the selection of an appropriate mud weight, as a controllable parameter, can significantly reduce these issues. The primary objective of this study is to utilize the finite difference numerical method to investigate wellbore stability caused by drilling in a dolomitic region within the Kangan formation. Initially, the geomechanical parameters required for simulation were determined using laboratory and wellbore test results. Subsequently, numerical modeling of the well was performed using FLAC۳D software, employing a fully coupled fluid-flow and mechanical solution approach based on the Mohr-Coulomb failure criterion. Stress and pore pressure variations around the wellbore after drilling were determined, and stress concentration zones were identified. The model's validity was evaluated by comparing the plastic zone obtained from numerical modeling with the actual conditions observed within the well, showing acceptable agreement. Furthermore, the severity of wellbore stability was assessed using the normalized yield zone area (NYZA), defined as the ratio of the plastic zone area to the wellbore area. The impact of varying mud weight on a section of the well was also examined. The results indicate that increasing the mud weight reduces displacements and the plastic zone around the wellbore but does not mitigate the tangential stress effect near the wellbore wall.

کلیدواژه ها:

Numerical Analysis ، Wellbore stability ، Mud weight ، Geomechanical parameters