Subsea processing of well fluids

Patent metadata

Field	Value
Publication number	US-9644457-B2
Application number	US-201314654545-A
Country	US
Kind code	B2
Filing date	Dec 17, 2013
Priority date	Dec 21, 2012
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

A towable unit for subsea processing of well fluids comprises a pipeline bundle extending between, and capable of acting in tension between, a first towhead at an upstream end of the bundle and a second towhead at a downstream end of the bundle. At least one of the towheads has an on-board processing facility for processing the well fluids, which facility effects at least separation of water phases that are present in the well fluids.

First claim

The invention claimed is:

1. A towable unit for subsea processing of well fluids, wherein the unit comprises a pipeline bundle extending between, and capable of acting in tension between, a first towhead at an upstream end of the bundle and a second towhead at a downstream end of the bundle, wherein the pipeline bundle comprises cooling and heating apparatus for controlling wax in the well fluids, wherein at least one of the towheads has an on-board processing facility for processing the well fluids, which facility effects at least separation of water phases that are present in the well fluids, and wherein at least one towhead has a pump for pumping cooling water along the pipeline bundle, to force wax deposits to form in the pipeline bundle.

2. The towable unit of claim 1 and comprising a power connection extending along the bundle to transfer power between the towheads.

3. The towable unit of claim 2 , wherein a power station is housed in the second, downstream towhead.

4. The towable unit of claim 3 , wherein an umbilical distribution system for distributing power and/or chemicals to external templates or satellite wellheads is housed in the second, downstream towhead.

5. The towable unit of claim 4 and comprising a data connection extending along the bundle to convey control data between the towheads.

6. The towable unit of claim 5 , wherein the on-board processing facility is housed in the first, upstream towhead.

7. The towable unit of claim 6 , wherein the first, upstream towhead also comprises facilities selected from a set comprising: connections to wellhead(s) or to a production manifold; water separation; removed water treatment and/or re-injection; cold flow conditioning for transportation; cold-water circulation systems; pigging facilities; and local heating systems for wax removal.

8. The towable unit of claim 7 , wherein at least one of the towheads has a heating system for applying heat to the pipeline bundle.

9. The towable unit of claim 8 , wherein the heating systems comprise power supplies for energising heating elements in the pipeline bundle.

10. The towable unit of claim 9 , wherein the pipeline bundle is a wax control element comprising a bundle of flowlines within an elongate tensile structure that defines inlet and outlet ends.

11. The towable unit of claim 10 , wherein the flowlines are disposed in parallel but connected in series within the tensile structure such that the well fluids reverse in flow direction between one flowline and the next within the element.

12. The towable unit of claim 11 , wherein the tensile structure is an outer pipe surrounding the flowlines.

13. The towable unit of claim 12 , wherein at least one of the towheads includes wellheads.

14. The towable unit of claim 13 , wherein at least one of the towheads includes an array of drilling slots.

15. A subsea oil or gas production system comprising at least one towable unit as defined in claim 1 .

16. A method of installing or developing a subsea oil or gas production system by installing a prefabricated processing unit at an installation location, the unit comprising a pipeline bundle disposed between a first towhead at an upstream end of the bundle and a second towhead at a downstream end of the bundle, the method comprising:
towing the processing unit to the installation location with the pipeline bundle in tension;
sinking the unit at the installation location; and
connecting the towheads to other elements of the production system so that the processing unit is operated to process well fluid and to pass the well fluid along the pipeline bundle,
wherein processing of the well fluid comprises hydrate control performed in the first, upstream towhead;
wherein wax control is effected by passing well fluid along the pipeline bundle between the towheads while cooling and periodically heating pipes of the bundle, and wherein cooling comprises pumping cooling water along the pipeline bundle.

17. The method of claim 16 , wherein power and chemicals are distributed to templates and wellheads of the system from the second, downstream towhead.

Assignees

• Subsea 7 Norway As

Inventors

• Sathananthan Ratnam
• Daasvatn Sigbjorn

Classifications

• E21B41/08

  Underwater guide bases, e.g. drilling templates; Levelling thereof · CPC title

• B01D17/12

  Auxiliary equipment particularly adapted for use with liquid-separating apparatus, e.g. control circuits · CPC title

• E21B37/06

  using chemical means for preventing or limiting {, e.g. eliminating,} the deposition of paraffins or like substances · CPC title

• B01D17/042

  by changing the temperature · CPC title

• F16L1/165

  by towing the pipe on or near the bottom · CPC title