Heave disturbance attenuation in managed pressure drilling from a floating platform using model predictive control

Abstract

Since a large part of the Norwegian oil shelf has been active for over a generation, many fields begin to be depleted and the drilling operations requires tight down hole pressure margins. And by improving the pressure control for the drilling operations former undrillable wells becomes drillable. Which will make the the oilfields more profitable, and extend their life expectancy. It will also make drilling operations safer by preventing kicks and preventing environmental damages caused by mud leaking into the pore space.\\\\One of the most critical phases when drilling from a floating drilling rig in terms of down hole, is pipe connection. During this procedure the conventional heave compensation is not operational as the drill string is climbed to the drill floor. Consequently the drill bit functions as a piston creating large pressure variations in the drill bit pressure. To control this pressure and create disturbance attention a linear model predictive controller with feedback linearisztion is created using feedback linearization. This controller shows promising results when feedforward with future predictions is applied. Without future predictions the results are the same as for an MPC without feedforward. Because only the topside pressure is known the rest of the states are estimated using a Kalman filter, which shows good results on the state estimations. To make the system more applicable in real life applications an efficient linear model predictive controller implementation was created for a PLC with great results, both in terms of calculation time and memory usage.