Sammendrag
Good flow and pressure control is essential for successful Underbalanced Drilling (UBD) operations. This work evaluates the use of Model Predictive Control (MPC) for
integrated control of well conditions and the topside separation system during UBD. The
downhole well pressure, separator liquid levels, and the separator pressure are controlled
by manipulation of the rig pump, the choke, and the separator valves. The control system
adheres to downhole and topside constraints. These constraints include pore and collapse
pressures, minimum flow rate for hole cleaning, maximum choke pressure, separator pressure,
and separator liquid levels. The proposed MPC solution uses simple Hammerstein-Wiener
models, where parameters are determined by system identification incorporated into standard
drilling procedures. The control system is tested using a high-fidelity multi-phase flow simulator
(OLGA) for some common drilling scenarios, including drilling into a producing formation and
performing connections. We show that the MPC solution is able to take proactive action to
ensure safe and efficient operation without having to enter well control mode or shutting down
the separator system. By limiting the amount and variation in influx from the reservoir, we get
less Non-Productive Time (NPT), we improve safety, and we may to some extent be able to
reduce the footprint of the equipment.
Vis fullstendig beskrivelse