Abstract: A system for drilling a subsea well from a rig through a subsea wellhead below the rig includes a wellhead stack which is mounted on the subsea wellhead. The wellhead stack includes at least a subsea blowout preventer stack and a subsea diverter. A drill string extends from the rig through the wellhead stack into the well to conduct drilling fluid from the rig to a drill bit in the well. A riser which has one end coupled to the wellhead stack and another end coupled to the rig internally receives the drill string such that a riser annulus is defined between the drill string and the riser. A well annulus extends from the bottom of the well to the subsea diverter to conduct fluid away from the drill bit. A pump has a suction side in communication with the well annulus and a discharge side in communication with the rig and is operable to maintain a selected pressure gradient in the well annulus.

Abstract: A rotating diverter for isolating fluid in a well from other fluid above the well is provided. The rotating diverter includes a housing body which has a bore running through it. A retrievable spindle assembly which includes a spindle and a bearing assembly is disposed in the bore. The bearing assembly supports the spindle for rotation. The spindle is adapted to receive and seal around a tubular member, and rotation of the tubular member rotates the spindle within the bore. A lock member is disposed in the housing body to secure the retrievable spindle assembly to the housing body.

Abstract: A positive-displacement pump includes multiple pumping elements, each pumping element having a pressure vessel with a first and a second chamber and a separating member disposed between the first and second chambers. The first chambers and the second chambers are hydraulically connected to receive and discharge fluid, wherein the separating members move within the pressure vessels in response to pressure differential between the first and second chambers. A valve assembly having suction and discharge valves communicates with the first chambers. The suction and discharge valves are operable to permit fluid to alternately flow into and out of the first chambers. A hydraulic drive alternately supplies hydraulic fluid to and withdraws hydraulic fluid from the second chambers such that the fluid discharged from the first chambers is free of pulsation.

Abstract: A choke valve with a power system operated via a single hydraulic line. The sleeve of the choke valve is operated by a carrier mounted through an eccentric pin and guide track arrangement to open and close the valve with the rotation of a valve drive shaft. A power shaft is driven by a clutch plate, ratchet connected to a drive clutch plate, in turn, operated by the shaft of an hydraulic actuator. The valve actuator creates an incremental step sensing of its full sixteenth turn movement by closing a fluid exhaust port and causing back pressure in the hydraulic line to occur. The actuator is reset by a pre-loaded torsion bar. Reset of the actuator also ratchet resets the drive clutch plate.