A managed pressure drilling system, used in conjunction with a continuous circulating device to control wellbore pressure, helped an international E&P company successfully drill a difficult section of an deepwater exploration well in Ghana, West Africa, in 2012. Combined, all MPD riser stack components should be automatically controlled by a central intelligent control unit responding to the unique wellbore signals being monitored, including return flow, to enable immediate detection of changes in fluid flow.
Drilling string DS extends through the RCD 10, BOP stack B, wellhead W, casing C, wellbore WB and casing shoe CS into the wellbore borehole BH. As used herein, casing rotator a wellbore WB may have casing in it or may be open (i.e., uncased as wellbore borehole BH); or a portion of it may be cased and a portion of it may be open.
The hull is typically a large cylindrical steel tube with a variety of internal compartments that provide buoyancy to support the topside drilling and production equipment with a central annulus (center well) through which all production is accomplished.
Is a cut away section elevational view of an RCD with a lower active sealing element and two upper passive sealing elements, sensors for measuring pressures and temperatures from the diverter housing and into, in and out of the RCD upper and lower internal cavities, and influent and effluent lines for communicating cavity fluid into, in and out of each RCD internal cavity.
In the DTTL method, since surface backpressure is constantly applied, the pore pressure limitation of the conventional drilling window, such as used in the CBHP method and other MPD methods, can be disregarded in developing the fluid and drilling programs.
It is important that the RCD remain static on the riser so that any rig movement does not cause pressure changes in the wellbore annulus, which may result in inaccurate flow measurement by the MPD system and make detection of kicks, losses, and ballooning considerably more difficult.
An operator may not wish to place such a demand on any one sealing element for a prolonged period, and therefore may periodically choose to adjust the pressures within the cavities of the RCD such that other sealing elements within the RCD are utilized as the "main or sacrificial" sealing element, even though the integrity of the original "main" sealing element may still be good.