# US 2019/0169968 A1 · Liquid retainer for a production system

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- Number: US 2019/0169968 A1
- Document ID: US20190169968A1
- Status: Published application
- Kind: A1
- Application number: 15/828,690
- Filed: 2017-12-01
- Published: 2019-06-06
- Earliest claimed: 2017-12-01
- Assignees: OneSubsea IP UK Limited
- Applicants: OneSubsea IP UK Limited
- Inventors: Stig Kaare Kanstad; Nils-Egil Kangas; Joakim Almqvist; Carl-Martin Carstensen
- Web page: https://patentgrep.com/patent/US20190169968A1

## CPC

- E21B 43/121: {Lifting well fluids (monitoring of down-hole pump systems E21B47/008)}
- E21B 41/04: Manipulators for underwater operations, e.g. temporarily connected to well heads
- E21B 43/01: specially adapted for obtaining from underwater installations
- E21B 43/32: Preventing gas- or water-coning phenomena, i.e. the formation of a conical column of gas or water around wells
- E21B 43/36: Underwater separating arrangements (E21B43/38 takes precedence)
- E21B 2200/09: Detecting, eliminating, preventing liquid slugs in production pipes
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS

## Abstract

An apparatus includes a seabed-disposed pump that includes an inlet to receive a fluid flow and an outlet. The apparatus includes a liquid retainer that is adapted to receive a fluid flow that is produced by a subsea well. The liquid retainer selectively retains and releases liquid from the fluid flow to regulate a gas volume fraction of the fluid flow that is received at the inlet of the pump.

## Claims

### Claim 1

An apparatus comprising:
a seabed-disposed pump comprising an inlet to receive a fluid flow and an outlet; and
a liquid retainer adapted to:
receive a fluid flow provided by a subsea well; and
selectively retain and release liquid from the fluid flow provided by the subsea well to regulate a gas volume fraction of the fluid flow received at the inlet of the pump.

### Claim 2 (depends on 1)

The apparatus of claim 1, wherein the liquid retainer comprises:
a vessel to store a liquid reservoir;
an inlet to communicate the fluid flow provided by the subsea well to the vessel;
a vessel outlet connected to the vessel above the liquid reservoir;
a drain outlet connected to the liquid reservoir; and
a third outlet to provide a gas volume fraction regulated flow to the pump, wherein the third outlet is connected to the vessel outlet and the drain outlet.

### Claim 3 (depends on 2)

The apparatus of claim 2, wherein the drain outlet has a cross-sectional flow area to supply liquid from the liquid reservoir to the third outlet based on the gas volume fraction of the fluid flow received at the inlet of the pump.

### Claim 4 (depends on 1)

The apparatus of claim 1, further comprising:
a sensor to provide a signal representing an amount of liquid in the liquid reservoir; and
controller to regulate operational speed of pump in response to the signal.

### Claim 5 (depends on 1)

The apparatus of claim 1, further comprising:
a recirculation fluid path connected between the inlet and the outlet of the pump, wherein the recirculation fluid path comprises a choke;
a sensor to provide a signal representing an amount of liquid in the liquid reservoir; and
a controller to regulate a cross-sectional flow area of the choke in response to the signal.

### Claim 6 (depends on 1)

The apparatus of claim 1, wherein the liquid retainer comprises:
a first vessel to store a first liquid reservoir;
an inlet to communicate the fluid flow provided by the subsea well to the first vessel;
a first vessel outlet connected to the first vessel above the first liquid reservoir;
a first drain outlet connected to the first liquid reservoir;
a second vessel to store a second liquid reservoir;
a second inlet connected to the second vessel outlet;
a second vessel outlet connected to the second vessel above the second liquid reservoir;
a second drain outlet connected to the second vessel and connected to the first vessel above the first drain outlet to cause liquid from the second reservoir to drain into the first reservoir; and
an outlet connected to the second vessel outlet and the first drain outlet to provide a flow to the inlet of the pump.

### Claim 7 (depends on 6)

The apparatus of claim 6, wherein the second liquid reservoir has a liquid height that is different than a liquid height of the fluid liquid reservoir.

### Claim 8 (depends on 7)

The apparatus of claim 7, wherein the liquid from the second liquid reservoir drains into the first reservoir at a rate based on a difference in the liquid heights.

### Claim 9 (depends on 1)

The apparatus of claim 1, wherein the liquid retainer comprises:
a first vessel to store a first liquid reservoir;
an inlet to communicate the fluid flow provided by the subsea well to the first vessel;
a first vessel outlet connected to the first vessel above the first liquid reservoir;
a first drain outlet connected to the first liquid reservoir;
a second vessel to store a second liquid reservoir;
a second inlet connected to the second vessel outlet;
a second vessel outlet connected to the second vessel above the second liquid reservoir;
a second drain outlet connected to the second vessel;
a flow path connected to the second vessel outlet, the first drain outlet and the second drain outlet; and
an outlet connected to the flow path to provide a gas volume fraction regulated flow to the pump inlet.

### Claim 10 (depends on 1)

The apparatus of claim 1, further comprising a flow line to communicate a flow from the liquid retainer toward the pump along a first direction,
wherein the liquid retainer comprises outlet to provide a gas volume fraction regulated flow to the flow line, and the liquid retainer comprises a nozzle to introduce the gas volume fraction regulated flow into the flow line in a second direction that opposes the first direction.

### Claim 11 (depends on 10)

The apparatus of claim 10, wherein the outlet comprises an opening outside of the nozzle to communicate particulates from the liquid retainer to the flow line.

### Claim 12 (depends on 10)

The apparatus of claim 10, wherein the nozzle comprises a conical nozzle or a cylindrical nozzle.

### Claim 13

An apparatus comprising:
a pump comprising an inlet and an outlet;
a recirculation path coupled between the inlet and the outlet of the pump; and
a flow splitter to receive a first flow and provide a flow to the inlet of the pump, the flow splitter comprising:
a receptacle to receive the first flow and retain a predetermined volume of liquid to regulate a gas volume fraction at the inlet of the pump.

### Claim 14 (depends on 13)

The apparatus of claim 13, wherein the receptacle comprises an opening to communicate particulates in the receptacle to the outlet of the vessel.

### Claim 15 (depends on 13)

The apparatus of claim 13, wherein the receptacle is adapted to decrease the retained volume to cause a gas volume fraction at the inlet of the pump to be less than a gas volume fraction in the first flow received by the flow splitter.

### Claim 16 (depends on 13)

The apparatus of claim 13, wherein the receptacle is adapted to increase the retained volume to cause a gas volume fraction at the inlet of the pump to be greater than a gas volume fraction in the first flow received by the flow splitter.

### Claim 17

A method usable with a well, comprising:
pumping production fluid from a subsea well to a surface platform; and
storing and releasing liquid associated with the communication of the production flow to regulate a gas volume fraction of the fluid flow.

### Claim 18 (depends on 17)

The method of claim 17, wherein storing and releasing fluid to regulate the gas volume fraction comprises using a liquid retainer disposed upstream of a pump.

### Claim 19 (depends on 17)

The method of claim 17, further comprising:
regulating an operational speed of a pump associated with the pumping based on a stored liquid level.

### Claim 20 (depends on 17)

The method of claim 17, wherein:
the pumping comprises recirculating a fluid flow between an outlet of a pump and an inlet of the pump; and
controlling the flow associated with the recirculation based on a fluid stored in a liquid retainer.