The specialization of managed-pressure drilling (MPD) equipment for surface and subsea applications is improving the performance of rotating control devices (RCDs) in land, surface and deepwater subsea applications, eliminating the need for RCDs. AFGlobal offers new application-specific MPD equipment that is designed to enhance safety and efficiency, and is releasing next-generation design concepts, materials and performance.
MPD sophistication
The equipment advances reflect the growing sophistication of MPD as a common, and often prerequisite, tool for modern wellbore construction. Demand has evolved two design paths for MPD-enabling RCD equipment: land and marine surface applications, and deepwater subsea applications.
The RCD directs the rig’s annular fluid returns into a series of chokes and instruments by sealing the annulus between the drillpipe and casing. Traditional RCD designs have achieved this with a rotating elastomer seal element and bearing assembly. The design is very effective, but has wear and maintenance requirements. In deepwater applications, high operational costs make these RCD expenses particularly significant.
AFGlobal, a manufacturer of MPD equipment and provider of MPD engineering services, has released a new design concept and materials technology to produce a nonrotating active control device that replaces the RCD in deepwater applications.
Surface application
In surface applications, the RCD is installed on top of the BOP stack. In deepwater systems, the RCD is installed subsea as an integral component of the drilling riser. The two applications present different economic and operational demands, which have produced unique variations for improving safety, time and efficiency.
In surface applications, AFGlobal L-Series RCD is a direct, cost-effective tool for implementing MPD operations based on decades of RCD manufacturing experience. The L-Series RCD is technology built and tested to API 16 A, API 16 RCD, and NACE standards. The device improves performance with an element and bearing assembly designed for long service and convenient maintenance.
Subsea application
Deepwater MPD has resulted in a significant departure from conventional RCD design that introduces a nonrotating device. AFGlobal’s active control device seals around the drillpipe with a nonrotating hydraulically controlled sealing sleeve. The sleeve is made possible by a co-molded element that features an enhanced urethane matrix reinforced with a durable polytetrafluoroethylene inner shell. As the sealing sleeve wears, pressure is actively applied to force the element against the drillpipe to maintain consistent seal performance.
Active pressure sealing is a significant advance over RCD operations that degrade the performance of a passive rotating elastomer seal. The new device varies hydraulic pressure on the seal to compensate for wear and accommodate passage of wear-inducing tool joints. In addition, active pressure is a positive wear indicator to inform maintenance and assure MPD operations. Service life and performance is further enhanced by the greater durability of the co-molded element and lubrication of the seal with drilling mud.
MPD integration
The active control device is a component of AFGlobal’s riser gas handling system (RGH), which is an integral part of the drilling riser. It is used to address safety issues that occur when formation gas breaks out of solution in the riser. It also is the basis for establishing an MPD-ready rig with the addition of manifolds, instrumentation, control systems and other MPD equipment. The component-based RGH easily accommodates MPD service company equipment in addition to AFGlobal MPD systems owned by the drilling contractor or operator.
AFGlobal provides a full scope MPD engineering support and MPD equipment. The NControl MPD platform integrates monitoring, data, control, analysis and automation. Its rig floor workstations provide an interface with systems components, including flowmeters, transmitters, sensors and valves. Specialized manifolds enable precise downhole pressure management and integration of mud returns with the rig system.
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