Adaptive estimation of downhole pressure for Managed Pressure Drilling operations

The objective of Managed Pressure Drilling (MPD) is to enable precise control of the downhole pressure during drilling and completion operations. An essential part of an automated MPD control system is the downhole pressure estimator, usually referred to as the hydraulic model, which in most cases is the limiting factor for achievable accuracy of the system. In this paper we present a new design of an adaptive observer for online estimation of the downhole pressure in the well. Unlike conventional hydraulic models, which are based on complex partial differential equations, the adaptive observer is based on a simplified lumped model of ordinary differential equations, combined with online adaptation that tunes uncertain model parameters utilizing topside measurements. We demonstrate that the novell adaptive observer design captures the important hydraulics of MPD operations with high accuracy, and fundamentally improves the convergence rate of the parameter estimates by using delayed observers. The results are demonstrated on field data from an offshore MPD operation.