Facility and method for underwater disposal of the water produced during underwater production of hydrocarbons at great depths

Patent metadata

Field	Value
Publication number	US-11828153-B2
Application number	US-202017610347-A
Country	US
Kind code	B2
Filing date	Apr 28, 2020
Priority date	May 23, 2019
Publication date	Nov 28, 2023
Grant date	Nov 28, 2023

Abstract

A facility for the subsea disposal of the water produced during deepwater hydrocarbon production, includes a subsea oil/water separation station fed with fluids coming directly from at least one hydrocarbon production well, operating at a pressure independent of and lower than the ambient pressure, and comprising an oil outlet for connecting to a production unit and a water outlet, a flat gravity oil/water separation tank resting on the seabed, continuously fed with water leaving the oil/water separation station, operating at a pressure substantially equal to the ambient pressure, and comprising an oil outlet for connecting to the production unit and a water outlet, and a subsea high-pressure pump connected to the water outlet of the oil/water separation station and to a water inlet of the tank to raise the pressure of the water leaving the oil/water separation station to the ambient pressure before it is admitted into the tank.

First claim

The invention claimed is:

1. A facility for subsea disposal of water produced during deepwater hydrocarbon production, comprising:
a subsea oil/water separation station fed with fluids coming directly from at least one hydrocarbon production well, operating at a pressure independent of and lower than the ambient pressure, and comprising an oil outlet for connecting to a production unit and a water outlet;
a flat gravity oil/water separation tank resting on the seabed, continuously fed with water leaving the oil/water separation station, operating at a pressure substantially equal to the ambient pressure, and comprising an oil outlet for connecting to the production unit and a water outlet; and
a subsea high-pressure pump connected, on the one hand, to the water outlet of the oil/water separation station and, on the other hand, to a water inlet of said tank to raise the pressure of the water leaving the oil/water separation station to the ambient pressure before the water is admitted into said tank.

2. The facility according to claim 1 , wherein the flat tank has a geometric configuration that allows a long residence time of the produced water, a low migration path for the oil droplets present in the water and a large oil/water interface area in order to promote oil/water separation by gravity.

3. The facility according to claim 2 , wherein the tank further comprises, at the top, an oil droplet collection device opening toward the oil outlet of the tank.

4. The facility according to claim 3 , wherein the tank further comprises, at the top, means for periodically discharging the oil present at the level of the collection device.

5. The facility according to claim 4 , wherein the means for periodically discharging the oil droplets comprises a network of suction pipes controlled by an on-off valve capable of opening into the collection device.

6. The facility according to claim 1 , wherein the tank further comprises, at the bottom, means for collecting and periodically discharging any solid particles deposited on a floor of the tank.

7. The facility according to claim 6 , wherein the means for collecting and discharging solid particles comprise a network of suction pipes controlled by a valve, and nozzles for injecting pressurized water toward the floor of the tank.

8. The facility according to claim 1 , wherein the oil outlet of the tank is connected to the oil outlet of the oil/water separation station via at least one on-off valve.

9. The facility according to claim 1 , wherein the water outlet of the tank opens into the sea via a low-pressure pump or opens into a water injection well via a high-pressure pump.

10. The facility according to claim 1 , wherein the tank has a cylindrical shape with a flat floor, an upwardly sloping roof to facilitate the collection of oil droplets, the water inlet which opens into the tank at the center thereof via a cyclonic device to impose an initial rotation speed on the water admitted into the tank, the oil outlet which is positioned at the level of the sloping roof, and the water outlet which comprises a plurality of scoops formed at the periphery of the tank and opening into the tank in tangential directions.

11. The facility according to claim 1 , wherein the tank has a plurality of pipes of large diameter and long length arranged parallel to each other, resting on a seabed, the water inlet of the tank being at a same inlet end of each pipe, and the oil outlet and the water outlet of the tank being at a same opposite outlet end of each pipe.

12. The facility according to claim 11 , wherein the seabed on which the tank rests has a horizontal slope, the pipes resting on the seabed so that their outlet end is tilted upwards relative to their inlet end.

13. The facility according to claim 11 , wherein the seabed on which the tank rests is horizontal, the pipes resting on the seabed via tilting means so that their outlet end is tilted upwards relative to their inlet end.

14. The facility according to claim 13 , wherein the tilting means comprises supports giving a tilt to the tank pipes resting thereon.

15. The facility according to claim 13 , wherein the tilting means comprises systems for anchoring to the seabed the inlet end of the pipes and float systems connected to the outlet end of the pipes to tilt them upwards relative to the inlet ends.

16. The facility according to claim 1 , wherein the tank has a pipe of large diameter and very long length, the water inlet of the tank being at an inlet end of the pipe which is anchored to the seabed, and the oil outlet and the water outlet of the tank being at the opposite outlet end of the pipe which is connected to floats to give the pipe a catenary shape.

17. The facility according to claim 11 , wherein each pipe has a loop, serpentine or spiral shape.

18. The facility according to claim 1 , wherein the tank comprises a single pipe forming a helix, the water inlet of the tank being at one inlet end of the pipe, and the oil outlet and the water outlet of the tank being at the opposite outlet end of the pipe.

19. The facility according to claim 1 , wherein the tank comprises a plurality of channels of parallelepipedal cross-section which are arranged in a helix, the water inlet of the tank being at a same inlet end of each channel, and the oil outlet and the water outlet of the tank being at a same opposite outlet end of each channel.

20. The facility according to claim 1 , wherein the tank comprises a plurality of identical tiles each in the form of a dihedral, inclined at 30° to the horizontal, and arranged in several series of tiles.

21. The facility according to claim 1 , wherein the high-pressure pump is a multi-stage coalescing pump.

22. The facility according to claim 1 , wherein the tank comprises a rigid shell.

23. A process for subsea disposal of water produced during deepwater hydrocarbon production, comprising feeding fluids coming directly from at least one hydrocarbon production well to a subsea oil/water separation station operating at a pressure independent of and lower than the ambient pressure and continuously feeding a flat gravity oil/water separation tank resting on the seabed with produced water leaving the oil/water separation station, the produced water feeding the tank having first been pressurized to reach a pressure substantially equal to the ambient pressure.

Assignees

• Saipem Sa

Inventors

• Capela Moraes Carlos Alberto
• Hallot Raymond
• Chazot Nicolas

Classifications

• E21B43/36 Primary

  Underwater separating arrangements (E21B43/38 takes precedence) · CPC title

• B01D17/0214

  with removal of one of the phases · CPC title

• B01D21/10

  Settling tanks with multiple outlets for the separated liquids · CPC title

• B01D21/2444

  Discharge mechanisms for the classified liquid · CPC title

• B01D21/2472

  Means for fluidising the sediments, e.g. by jets or mechanical agitators · CPC title