Patent ID: 9322230
Filing Date: 2016-04-26
CPC Classification: E21B

Claim Text:
1. A subsea mudlift pump, comprising: at least two pistons, each piston disposed in a respective separate pumped fluid chamber, the respective pumped fluid chambers being formed in one or more pressure sealed housings disposed in a body of water in which a wellbore is being drilled by a drilling rig disposed above the surface of the body of water; at least two motors, each motor being coupled to one of the pistons and operable to cause reciprocating linear motion of a respective one of the pistons within the respective pumped fluid chamber; a pressure sensor in pressure communication with a pump inlet for measuring pressure at the pump inlet; and a controller in signal communication with the pressure sensor, the controller being configured to operate the at least two motors to control the volume of each of the pumped fluid chamber and the respective speed of each of the pistons to provide a relative volume-phase relationship between the at least two separate pumped fluid chambers such that a pressure at the pump inlet has minimal variations and a discharge of the pump has minimal fluid pressure and/or flow rate variations.