Offshore Drilling Challenges Solved with Closed-Loop Systems
This process can be automated by the addition of a new control system. The system monitors and responds to complex sets of downhole pressure fluctuations much faster than humanly possible. Characterization or fingerprinting of pressure patterns discerns between common drilling events, such as connection gas and downhole events—even when circulation is stopped.
In deepwater environments, these capabilities are key to identifying gas breakout in the riser that occurs above subsea well control systems.
Offshore Automation and Integration
Two key technologies in the growing offshore use of closed-loop systems are automation and the recent integration of RCDs with marine risers. Automation is a proven enabler for offshore MPD operations during which even the best crew can be challenged by the response time necessary to mitigate complex downhole pressure sequences.
Kick/loss scenarios often exhibit rapid influx and loss oscillations. Managing these complex fluctuations requires an equally rapid response that is achieved only with automation. By quickly managing backpressure in small increments within the pressurized circulating system, the system can precisely balance wellbore pressures within predefined limits.
A faster automated response also improves drilling efficiencies and lowers fluid costs by providing the high degree of operational control needed to safely work at lower mud weights.
The second technology is a unique subsea RCD for riser installations. Integrating the RCD with the riser is a major fit-for-purpose achievement for deepwater applications.
A below tension ring (BTR) RCD is the first device to be deployed as a subsea riser component. Because the RCD is made up below the tension ring, no modifications are required to the riser’s telescoping slip joint.
The BTR design also limits human exposure to risk below the rig floor during RCD installation, maintenance and operation. Bearing and sealing element replacement is accomplished with a hydraulic latching system that does not require personnel in the moonpool area. A bearing assembly running tool and ancillary equipment provide for rig-floor positioning and removal.
Hydraulic and electrical connections are made below the waterline, using a subsea-rated hydraulic stab plate. Multiport connections speed the deployment and makeup of hydraulic and electrical lines.