Buoyant system and method with buoyant extension and guide tube

Patent metadata

Field	Value
Publication number	US-10655437-B2
Application number	US-201815922350-A
Country	US
Kind code	B2
Filing date	Mar 15, 2018
Priority date	Mar 15, 2018
Publication date	May 19, 2020
Grant date	May 19, 2020

Abstract

The present invention provides a buoyant system and method for a hydrocarbon offshore floating platform to be coupled and decoupled from a subsea buoyant extension with risers slidably coupled thereto. The buoyant system can allow rigid risers to be coupled and decoupled and alternatively move between a first elevation below the offshore floating platform, such as at the buoyant extension, and a higher second elevation at the offshore floating platform independent of a spool piece, arch support, and flexible joint for the risers. The buoyant system can reduce riser stress by reducing bending required for the riser to form a catenary or other curved shape even as a rigid riser.

First claim

What is claimed is:

1. A buoyant system configured to be detachable from an offshore floating platform, comprising:
a buoyant extension having a buoyancy and configured to be detachably coupled with the offshore floating platform; and
a first guide tube coupled to the buoyant extension and configured to allow a rigid portion of a riser to pass through the guide tube alternatively between a first elevation below the offshore floating platform and a higher second elevation at the offshore floating platform and allow the rigid portion of the riser to descend to the first elevation below the offshore floating platform while sliding through the first guide tube on the buoyant extension.

2. The system of claim 1 , wherein the buoyant extension comprises an extension upper portion.

3. The system of claim 2 , wherein the extension upper portion is configured to provide a buoyancy to the buoyant extension.

4. The system of claim 1 , wherein the buoyant extension comprises members having buoyancy.

5. The system of claim 1 , wherein the buoyant extension comprises a truss configured to allow water to laterally flow through the buoyant extension.

6. The system of claim 1 , wherein the buoyant extension is configured to guide the rigid portion of the riser at a nonvertical angle independently of a spool piece, arch support, and flexible joint for the riser.

7. The system of claim 1 , wherein the system further comprises the riser, and wherein the riser is a rigid riser from a subsea production equipment to be coupled to the offshore floating platform.

8. The system of claim 1 , further comprising a second guide tube coupled to the buoyant extension at a different angle than the first guide tube.

9. The system of claim 1 , further comprising a buoyancy module configured to be coupled to the riser at an elevation below the buoyant extension.

10. The system of claim 1 , further comprising a plurality of mooring lines coupled to the buoyant extension and configured to moor the floating platform when the floating platform is coupled with the buoyant extension.

11. The system of claim 1 , wherein the system further comprises the riser, and wherein the riser comprises at least a flexible portion below the buoyant extension.

12. The system of claim 1 , wherein the buoyant extension comprises a riser guide structure configured to guide a plurality of risers.

13. A floating platform coupled with the buoyant system of claim 1 , wherein the floating platform comprises a topsides with a valve, and wherein the riser from the buoyant extension is configured to be fluidicly coupled with the valve.

14. A floating platform coupled with the buoyant system of claim 1 , wherein the floating platform comprises a topsides with a well tree, and wherein the riser from the buoyant extension is configured to be fluidicly coupled with the well tree.

15. A method of using an offshore floating platform with a buoyant system having a buoyant extension and a first guide tube coupled to the buoyant extension and configured to allow a rigid portion of a riser to be moved through the guide tube alternatively between a first elevation below the offshore floating platform and a higher second elevation at the floating platform, and wherein the riser has been coupled through the guide tube on the buoyant extension to the floating platform, the method comprising:
disconnecting the riser from the floating platform;
allowing the rigid portion of the riser to descend to the first elevation below the offshore floating platform while sliding through the first guide tube on the buoyant extension;
disconnecting the floating platform from the buoyant extension with the riser remaining on the buoyant extension; and
moving the floating platform to a location other than a location of the buoyant extension.

16. The method of claim 15 , wherein allowing the riser to slide through the first guide tube on the buoyant extension comprises allowing the rigid portion of the riser to descend below the buoyant extension at a nonvertical angle independent of a spool piece, arch support, and flexible joint for the riser.

Assignees

• Technip France

Inventors

• Sablok Anil Kumar
• Lu Xiaohua

Classifications

• E21B17/015

  Non-vertical risers, e.g. articulated or catenary-type · CPC title

• E21B43/0107 Primary

  Connecting of flow lines to offshore structures (E21B43/013 takes precedence) · CPC title

• E21B19/004

  supporting a riser from a drilling or production platform · CPC title

• B63B35/4413

  Floating drilling platforms, e.g. carrying water-oil separating devices · CPC title

• E21B17/012 Primary

  with buoyancy elements (E21B17/015 takes precedence) · CPC title