Supervisory control for underbalanced drilling operations

Abstract

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.

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

“…The essential time scale associated to these dynamics can be in the range of tens of seconds, or even minutes in the case of gas influx into the wellbore. Not only can such dynamics deteriorate the control performance, but they can also cause instability (Pedersen et al 2015), if not accounted for during the controller design stage;…”

Internet of underground things‐assisted performance evaluation for underbalanced drilling telemetry systems

“…The reasonable transmission of UBD data is well-known to be problematic for mud-pulse telemetry (MPT) as the highly constrainable fluid for drilling used in UBD causes a dramatic increase in the attenuation of the MPT signal. 16 The ability to make sounds for judgment is very necessary to succeed in the implementation of UBD technology. Because of the complex nature of the implementation of the telemetry method, a closed mathematical expression is not feasible.…”

“…Today telecommunications are primarily preferred for UBD operations with electromagnetic, 15 acoustic, and connectors. The reasonable transmission of UBD data is well‐known to be problematic for mud‐pulse telemetry (MPT) as the highly constrainable fluid for drilling used in UBD causes a dramatic increase in the attenuation of the MPT signal 16 …”

Review of two-phase flow models for control and estimation

“…Model identification techniques were used to obtain 1st-order delay models for control of UBO using MPC by Pedersen and Godhavn (2013), with extensions in Pedersen et al (2015). This is similar to the technique used in (Nygaard et al, 2007b) where a NMPC controller was designed based on identified time constants.…”