Title: Modeling and Optimization of Hole Cleaning in Extended Reach Wells: Integrated Rheological and Operational Analysis Using WELLPLAN
Authors: Victoria Akuchukwu Umejuru, LoveGod Anthony Eke
Volume: 10
Issue: 7
Pages: 143-159
Publication Date: 2026/07/28
Abstract:
Efficient hole cleaning remains one of the most critical operational challenges in highly deviated and extended reach wells, where conventional gravitational cuttings transport is severely compromised. This study presents a comprehensive investigation of the hydromechanical and rheological factors influencing cuttings transport, bed formation, and suspension efficiency in deviated wellbores. The research integrates analytical, numerical, and simulation-based approaches, leveraging advanced drilling hydraulics modeling in WELLPLAN to quantify the impact of drilling fluid properties, well trajectory, and operational parameters on hole cleaning performance. Specifically, the study examines the roles of drilling fluid rheology including plastic viscosity, yield point, gel strength, and density on the suspension and transport of solids under varying annular flow conditions, flow regimes, and well inclinations. Operational variables, such as drill pipe rotation, flow rate modulation, rate of penetration (ROP), and circulation interruptions, were systematically evaluated to assess their influence on cuttings mobilization, erosion time, and critical velocity thresholds. Simulation results reveal that optimal hole cleaning is achieved through a synergistic combination of moderate plastic viscosity, appropriately weighted mud, and flow rates sufficient to maintain turbulent or pseudo-turbulent regimes, particularly in horizontal sections exceeding 60° deviation. Excessively high viscosity or sub-critical annular velocities were identified as primary contributors to cuttings bed formation, increased torque and drag, and potential stuck pipe events. The study further establishes threshold operational parameters, including minimum annular velocities and mud weight windows, necessary to prevent bed accumulation while minimizing Equivalent Circulating Density (ECD) and formation fracturing risks. Sensitivity analyses highlight the relative importance of fluid rheology versus mechanical agitation (pipe rotation) in mitigating cuttings deposition across different deviated well geometries. This work provides a robust framework for the integrated design of drilling fluid systems and operational practices in complex wellbores, offering predictive insights for real-time drilling optimization and risk mitigation. The findings have direct implications for the planning and execution of extended reach drilling projects, particularly in mature petroleum provinces such as the Niger Delta, where wellbore stability and operational efficiency are constrained by challenging formation conditions and narrow drilling margins.