Limitations of Topside Actuation for Rejecting Heave-induced Pressure Oscillations in Offshore Drilling

Abstract

The heave motion of a floating rig induces pressure oscillations in the well when the heave compensators are disabled during connections. In this paper we discuss several factors affecting the achievable performance when rejecting such pressure oscillations by feedforward by controlling the opening of the topside choke. Here, the well is modeled as a semilinear hyperbolic system with a predictor-based control law that achieves exact pressure tracking at one location in the well in the nominal case. The focus is on wells with large friction (i.e. deep wells with high-viscosity drilling muds), where large control inputs are required at the topside choke.