Modeling and Numerical Implementation of Managed-Pressure-Drilling Systems for the Assessment of Pressure-Control Systems

Automated managed-pressure drilling (MPD) is a method to enhance downhole pressure-control performance and safety during drilling operations. It is becoming more common to use model-based simulation for the evaluation of pressure-control systems designed for MPD automation before using those in the field. This demands a representative hydraulics-simulation model that captures the relevant aspects of a drilling system. This paper presents such a model and an approach to numerically implement that model for simulation studies. The complexity of this simulation model should be limited, first, to support effective numerical implementation and, second and most importantly, to allow for the analysis of the behavior and performance of the automated pressure-control systems during the controller-design phase. To this end, aspects of a drilling system that can considerably affect the performance of the automated MPD system are captured in the model. This hydraulics model incorporates both the distributed and multiphase-flow nature of a drilling system. Moreover, it captures nonlinear boundary conditions at the inlet of the drillstring, at the drill bit, and choke manifold, and also the variations in the cross-sectional area of the flow path. Model validations against field data from real-life MPD operations and simulations of industry-relevant scenarios indicate that these aspects are effectively captured in the model and preserved during the numerical implementation.