Offshore Drilling Challenges Solved with Closed-Loop Systems
The solution to many modern drilling challenges involves a fundamental change to one of the rig’s core components—the circulating system. Shifting from a traditional system that is open to the atmosphere to a closed-loop system requires only a few changes to common hardware. It yields significant new capabilities to monitor downhole pressures and contain, control and manage annular flow. The result is a significant improvement in safety, operational capabilities and well economics.
In offshore applications, scalable closed-loop systems and specialized marine technologies are increasing efficiencies and opening new reservoirs to development.
The industry’s first subsea rotating control device (RCD) extends these benefits to deepwater operations. Closed-loop capabilities as a well control barrier promise to further advance offshore use.
Subsea rotating control device
Closed-loop drilling systems are fully scalable from early kick and loss detection to wellbore control and management. This versatility provides answers to many issues that have long frustrated traditional offshore drilling operations, including expensive kick/loss episodes, total circulation losses and narrow pore-pressure/fracture-gradient windows.
The basic capability of a closed-loop system is early kick and loss detection (EKLD) to mitigate kick/loss events that can double and triple rig time and can escalate to devastating well control events.
Kick/loss cycles are often difficult to mitigate with traditional measures. Managing mud weight can be a slow response to equally slow and imprecise kick detection. However, within a closed-loop system, the drilling fluid provides a unique and immediate window to the wellbore. A kick or loss is detected as it occurs, so mitigation—conventional or managed pressure drilling (MPD)—can begin quickly before the problem escalates.
The step up to MPD occurs with the use of a choke manifold to manipulate surface pressure. This method has the same effect on equivalent circulating density as changes in mud weight.
Unlike the slow processes of circulating a column of modified density mud into the wellbore (as would be performed in conventional drilling systems) the backpressure imparted by MPD equipment is transmitted through the entire fluid column in seconds to counteract influxes or losses.