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. In this scenario, the material and configuration of the material used in each sealing element may be selected such that those identified for primary use while pulling the drill string out of the wellbore may be constructed of a more abrasion-resistant material than those sealing elements selected for primary use while drilling.
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 casing oscillator method 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.
Supplying a predetermined fluid pressure in a second cavity defined by the rotating control device inner member, the rotating control device second sealing element and the rotating control device third sealing element when said second sealing element and said third sealing element are sealed on the tubular.
This is, in part, because hydraulic drilling usually involves smaller hole sizes requiring smaller drill string diameters, smaller OD and lighter BHAs, and smaller mud systems and pumps that require only the circulation rates necessary to clean the hole.
For example, in a multi-seal RCD, one or more sealing elements may be primarily employed to contain the wellbore pressure during the drilling phase - i.e., while the bit is rotating at the bottom of the wellbore, and the open hole section is being extended.
However, the casing shoe pressure integrity may be less than the formation fracture pressure when drilling offshore, such as in geologically young particulate sediments, through salt domes, whose yielding characteristics challenge the ability to obtain an acceptable casing and casing shoe cement job.
American Petroleum Institute Specification 16RCD (API-16RCD) entitled "Specification for Drill Through Equipment - Rotating Control Devices," First Edition, © February 2005 American Petroleum Institute, proposes standards for safe and functionally interchangeable RCDs.
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.
Is a cut away section elevational view of an RCD with two passive sealing elements above an independent active sealing element, sensors for measuring pressures and temperatures in the diverter housing and the RCD upper and lower internal cavities, upper and lower RCD internal cavity pressure regulators and ports in the RCD bearing assembly for communicating cavity fluid with each RCD internal cavity.
Such phases may include running a drill string into the wellbore, drilling ahead while rotating the drill string, drilling ahead while not rotating the drill string (i.e., when a mud motor is used to rotate the drill bit), drilling ahead across a geological boundary into a zone exhibiting higher or lower pressure, reciprocation of the drill string, pulling a drill string out of the wellbore, etc.