Fluid transfer device usable in managed pressure and dual gradient drilling

Abstract

A fluid transfer device for use in wellbore drilling includes at least one pressure vessel having a fluid port at a bottom thereof for entry and discharge of one of a working fluid or a power fluid and a fluid port at a top thereof for entry and discharge of the other of the power fluid or the working fluid. The pressure vessel has a barrier fluid between the power fluid and the working fluid. Valves are coupled to the power fluid port for selective introduction of the power fluid into the at least one pressure vessel. Valves are coupled to the working fluid port such that the working fluid is constrained to flow in only one direction.

What is claimed is: 
     
         1 . A fluid transfer device for use in wellbore drilling, comprising:
 at least one pressure vessel having at least one fluid port proximate bottom thereof for entry and discharge of one of a working fluid or a power fluid and at least one fluid port proximate a top thereof for entry and discharge the other one of a power fluid or a working fluid;   wherein the pressure vessel has a barrier fluid disposed between the power fluid and the working fluid, the barrier fluid having a specific gravity intermediate a specific gravity of the power fluid and a specific gravity of the working fluid, the power fluid having a different specific gravity than the working fluid;   valves coupled to the power fluid port for selective introduction of the power fluid into the at least one pressure vessel; and   valves coupled to the working fluid port such that the working fluid is constrained to flow in only one direction.   
     
     
         2 . The fluid transfer device of  claim 1  further comprising a flow diffuser proximate a top of the interior of the at least one pressure vessel to reduce jetting of the power fluid and consequent mixing of the power fluid and the working fluid. 
     
     
         3 . The fluid transfer device of  claim 1  wherein the barrier fluid is phobic with respect to the power fluid. 
     
     
         4 . The fluid transfer device of  claim 1  wherein the barrier fluid is phobic with respect to the working fluid. 
     
     
         5 . The fluid transfer device of  claim 1  wherein the barrier fluid has a viscosity, polar/non polar solvent activity and surface tension properties such that the barrier fluid remains in a single contiguous mass during movement of the power fluid and the working fluid through the at least one pressure vessel. 
     
     
         6 . The fluid transfer device of  claim 1  wherein one of the valves coupled to the working fluid inlet is coupled to a drilling mud outlet of a subsea wellbore. 
     
     
         7 . The fluid transfer device of  claim 1  wherein one of the valves coupled to the working fluid port is coupled to a mud return line extending to a drilling vessel on the surface of a body of water. 
     
     
         8 . The fluid transfer device of  claim 1  wherein the power fluid comprises sea water. 
     
     
         9 . The fluid transfer device of  claim 1  further comprising an adjustable choke disposed in a power fluid discharge line to control a rate of fluid transfer. 
     
     
         10 . The fluid transfer device of  claim 1  further comprising a pump coupled at its intake to a power fluid discharge such that a pressure of the power fluid discharge is maintainable below a hydrostatic pressure of a body of water at a depth at which the fluid transfer device is disposed. 
     
     
         11 . The fluid transfer device of  claim 1  further comprising at least one disk disposed proximate the barrier fluid, the at least one disk having a specific gravity such that the at least one disk is disposed at a selected elevation with respect to the power fluid, the barrier fluid and the working fluid. 
     
     
         12 . The fluid transfer device of  claim 11  further comprising at least two disks spaced apart from each other by at least one link. 
     
     
         13 . The fluid transfer device of  claim 12  wherein a first one of the at least two disks has a specific gravity lower than a second one of the at least two disks such that the at least two disks such that the first one of the at least two disks is disposed proximate an interface between the barrier fluid and the power fluid and the second one of the at least two disks is disposed proximate an interface between the barrier fluid and the working fluid. 
     
     
         14 . The fluid transfer device of  claim 11  wherein the at least one disk has a diameter to thickness ratio so to ensure the upper and lower surfaces of the at least one disk remain substantially perpendicular to a longitudinal axis of the at least one pressure vessel and a direction of motion of the at least one disk within the at least one pressure vessel. 
     
     
         15 . The fluid transfer device of  claim 1  wherein the power fluid has a lower specific gravity than the working fluid and wherein the power fluid enters the at least one port on the top of the at least one pressure vessel.