Electric submersible pump (ESP) two-phase processor

1 . An electric submersible pump (ESP) assembly, comprising:

an electric motor having a first drive shaft;

a seal unit having a second drive shaft coupled to the first drive shaft of the electric motor and disposed uphole of the electric motor;

a first gas separator having a third drive shaft coupled to the second drive shaft and disposed uphole of the seal unit, wherein the first gas separator comprises a first cross-over, wherein the first cross-over defines a first gas phase discharge port and a first liquid phase discharge port;

a second gas separator having a fourth drive shaft coupled to the third drive shaft and disposed uphole of the first gas separator, wherein the second gas separator comprises a second cross-over, wherein the second cross-over defines a second gas phase discharge port and a second liquid phase discharge port;

a third gas separator having a fifth drive shaft coupled to the fourth drive shaft and disposed uphole of the second gas separator, wherein the third gas separator comprises a third cross-over, wherein the third cross-over defines a third gas phase discharge port and a third liquid phase discharge port, wherein the first gas separator is rated to have a first fluid flow rate, the second gas separator is rated to have a second fluid flow rate, the third gas separator is rated to have a third fluid flow rate, and the second fluid flow rate is less than or equal to 85% of the first fluid flow rate and less than or equal to 85% of the third fluid flow rate; and

a centrifugal pump assembly having a sixth drive shaft coupled to the fifth drive shaft and disposed uphole of the third gas separator, wherein the centrifugal pump assembly comprises a plurality of centrifugal pump stages and wherein each centrifugal pump stage comprises an impeller coupled to the sixth drive shaft and a diffuser retained by a housing of the centrifugal pump assembly.

2 . The ESP assembly of claim 1 , wherein the first gas separator comprises:

a first fluid mover mechanically coupled to the third drive shaft and having a fluid inlet and a fluid outlet;

a fluid reservoir concentrically disposed around the third drive shaft and located uphole of the first fluid mover, wherein an inside surface of the fluid reservoir and an outside surface of the third drive shaft define a first annulus that is fluidically coupled to the fluid outlet of the first fluid mover;

a second fluid mover having a fluid inlet and a fluid outlet, wherein the second fluid mover is located uphole of the fluid reservoir, and wherein the fluid inlet of the second fluid mover is fluidically coupled to the first annulus;

a separation chamber concentrically disposed around the third drive shaft and located uphole of the second fluid mover and downhole of the first cross-over, wherein an inside surface of the separation chamber and the outside surface of the third drive shaft define a second annulus that is fluidically coupled to the fluid outlet of the second fluid mover and is fluidically coupled to the first gas phase discharge port and to the first liquid phase discharge port.

3 . The ESP assembly of claim 2 , wherein the first annulus is a portion of the fluid reservoir that does not enclose a radial support of the third drive shaft, wherein when the third drive shaft is about 0.6875 inches in diameter, the first annulus has a volume of at least 70 cubic inches and less than 100 cubic inches; wherein when the third drive shaft is about 0.875 inches in diameter, the first annulus has a volume of at least 85 cubic inches and less than 120 cubic inches; wherein when the third drive shaft is about 1.0 inches in diameter, the first annulus has a volume of at least 180 cubic inches and less than 250 cubic inches; and wherein when the third drive shaft is about 1.1875 inches in diameter, the first annulus has a volume of at least 220 cubic inches and less than 300 cubic inches.

4 . The ESP assembly of claim 3 , wherein the fluid reservoir is at least 6 inches long and less than 17 inches long.

5 . The ESP assembly of claim 1 , wherein the first fluid flow rate is greater than 7,100 barrels per day and less than 50,000 barrels per day.

6 . The ESP assembly of claim 5 , wherein the second fluid flow rate is less than 6,000 barrels per day and greater than 20 barrels per day.

7 . The ESP assembly of claim 1 , further comprising a production tubing uphole of the centrifugal pump assembly and fluidically coupled to an outlet of the centrifugal pump assembly and a packer disposed around the production tubing.

8 . A method of lifting reservoir fluid by an electric submersible pump (ESP) assembly, comprising:

placing an electric submersible pump (ESP) assembly in a wellbore, wherein the ESP assembly comprises an electric motor, a seal unit disposed uphole of the electric motor, a first gas separator disposed uphole of the seal unit and having a first cross-over that comprises a first gas-phase discharge port and a first liquid-phase discharge port, a second gas separator disposed uphole of the first gas separator and having a second cross-over that comprises a second gas-phase discharge port and a second liquid-phase discharge port, a third gas separator disposed uphole of the second gas separator and having a third cross-over that comprises a third gas-phase discharge port and a third liquid-phase discharge port, and a centrifugal pump assembly disposed uphole of the third gas separator;

feeding a portion of a first reservoir fluid received from the wellbore via a fluid intake by the first gas separator to the second gas separator via the first liquid-phase discharge port of the first cross-over;

mixing by the second gas separator the portion of the first reservoir fluid fed through the first liquid-phase discharge port to the second gas separator with a second reservoir fluid received by the second gas separator from the wellbore via the second gas-phase discharge port of the second cross-over to form a third reservoir fluid;

feeding the third reservoir fluid by the second gas separator via the second liquid-phase discharge port of the second cross-over to the third gas separator;

feeding a portion of the third reservoir fluid by the third gas separator via the third liquid-phase discharge port to the centrifugal pump assembly; and

lifting by the centrifugal pump assembly the portion of the third reservoir fluid fed by the third gas separator via the third liquid-phase discharge port to the centrifugal pump assembly to a wellhead at a surface location.

9 . The method of claim 8 , wherein the second gas separator is configured to support a fluid flow rate in the range from 20 barrels per day to 6,000 barrels per day.

10 . The method of claim 9 , wherein the third gas separator is configured to support a fluid flow rate in the range from 7,100 barrels per day to 50,000 barrels per day.

11 . The method of claim 8 , wherein placing the ESP assembly in the wellbore comprises lowering the ESP assembly into the wellbore by a production tubing that connects to a discharge disposed at an uphole end of the centrifugal pump, further comprising setting a packer in the wellbore, wherein the packer seals against an inside of the wellbore and against an outside of the production tubing.

12 . The method of claim 8 , wherein the second gas-phase discharge port of the second cross-over is adjustable.

13 . The method of claim 8 , wherein the third reservoir fluid comprises a mix of liquid-phase fluid and gas-phase fluid at least part of the time the ESP assembly operates in the wellbore.

14 . A method of assembling an electric submersible pump (ESP) assembly at a wellbore location, comprising:

coupling a first drive shaft disposed in an electric motor to a second drive shaft disposed in a seal unit;

coupling an uphole end of the electric motor to a downhole end of the seal unit;

coupling the second drive shaft to a third drive shaft disposed in a first gas separator, wherein the first gas separator comprises a first cross-over having a first gas-phase discharge port and a first liquid-phase discharge port;

coupling the third drive shaft to a fourth drive shaft disposed in a second gas separator, wherein the second gas separator comprises a second cross-over having a second gas-phase discharge port and a second liquid-phase discharge port;

coupling the fourth drive shaft to a fifth drive shaft disposed in a third gas separator, wherein the third gas separator comprises a third cross-over having a third gas-phase discharge port and a third liquid-phase discharge port, wherein the first gas separator is rated to have a first fluid flow rate, the second gas separator is rated to have a second fluid flow rate, the third gas separator is rated to have a third fluid flow rate, and the second fluid flow rate is less than or equal to 85% of the first fluid flow rate and less than or equal to 85% of the third fluid flow rate;

coupling the fifth drive shaft to a sixth drive shaft disposed in a centrifugal pump assembly; and

lowering the electric motor, the seal unit, the first gas separator, the second gas separator, the third gas separator, and the centrifugal pump assembly into the wellbore.

15 . The method of claim 14 , wherein the wellbore location is offshore.

16 . The method of claim 14 , wherein the wellbore location is on land.

17 . The method of claim 14 , wherein lowering the electric motor, the seal unit, the first gas separator, the second gas separator, the third gas separator, and the centrifugal pump assembly into the wellbore comprises hanging the electric motor, the seal unit, the first gas separator, the second gas separator, the third gas separator, and the centrifugal pump assembly from a production tubing and above a horizontal portion of the wellbore.

18 . The method of claim 17 , further comprising setting a packer in the wellbore above the centrifugal pump assembly, wherein the packer seals against an inside of the wellbore and against an outside of the production tubing.

19 . The method of claim 14 , wherein the wellbore is a hydrocarbon production well.

20 . The method of claim 14 , further comprising adjusting an adjustable opening of the second gas-phase discharge port of the second cross-over.