A first-principles directional drilling simulator for control design
Leonard, Rebecca Leigh
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A directional drilling simulator was constructed using a re-formulation of first-principles classical mechanics in order to serve as a platform for advanced control design. Dedicated focus was placed on building a modular solution that would interface with an existing Supervisory Control And Data Acquisition (SCADA) architecture. Model complexity was restricted to include only the features required to make an immediate step change in tool face control performance through more accurate determination of torsional dead time and time constant values. Development of this simulator advanced the art of drilling automation by building a foundation upon which developers may design novel control schemes using big data gathered in the modern oilfield. This first-principles model is supported by theoretical formulation of equations of motion that capture fundamental behavior of the drill string during both rotary and slide drilling operations. Wellbore trajectory was interpolated between survey points using the Minimum Curvature Method, and a semi-soft-string drill string model was assumed. Equations of motion were derived using energy methods captured in both Hamiltonian and Lagrangian mechanics and solved using the finite-element method. Transient dynamic solutions were obtained using Newmark integration methods. A sensitivity analysis was conducted to determine which parameters played the most influential roles in dynamic drill string behavior for various operational scenarios and to what extent those parameters influenced torsional dead time and time constant calculations. The torsional time constant was chosen as a measure of correlation between case studies, due to the significant role this value plays in state-of-the-art tool face control algorithms. Simulation results were validated using field data collected from rigs using a SCADA system to operate in various shale plays in North America. Results from field tests were used to compare torsional time constant values calculated using manually-determined, simulation-based, and analytical methods and investigate directional drilling performance over a range of operational scenarios. Simulation-based time constant calculation results were consistently more accurate than analytically-determined values when compared to manually-tuned values. The first-principles directional drilling simulator developed for this study will be adopted by the existing SCADA system in order to standardize and improve slide drilling performance.