Reusable offshore platform jacket

• US 5,445,476 A
• Filed: 09/30/1993
• Issued: 08/29/1995
• Est. Priority Date: 09/30/1993
• Status: Expired due to Term

• Current Assignee: Shell Offshore, Inc. (Shell Plc)
• Original Assignee: Shell Oil Company (Shell Plc)
• Inventors: Gallaher, Dale M., Sgouros, George E.
• Primary Examiner(s): Reese, Randolph A.
• Assistant Examiner(s): Ricci, John A.
• Application Number:
  US08/129,829
• Time in Patent Office: 698 Days
• Field of Search: 405/195.1, 405/196, 405/203, 405/204, 405/222, 405/223, 405/224, 405/224.2, 405/225-228, 403/5, 403/31, 285/294, 285/297, 285/382.4, 285/382.5, 403/265, 403/268, 403/269, 29/507, 29/523
• US Class Current: 405/224
• CPC Class Codes: E02B 17/00 Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor construction methods for floating platforms B63B75/00; anchoring floating platforms B63B21/00; floating platforms, e.g. anchored, B63B35/44; underwater reservoirs B65D88/78
• CPC Class Codes: E02B 17/021 with relative movement between supporting construction and platform
• CPC Class Codes: E02B 2017/0043 Placing the offshore structure on a pre-installed foundation structure
• CPC Class Codes: E02B 2017/0052 Removal or dismantling of offshore structures from their offshore location

Abstract

The present invention is a reusable jacket base for an offshore platform having a plurality of jacket legs with an interconnecting framework. Pile sleeves are connected to the jacket legs which have a vertically extended, open-ended cylindrical member having a second stage sleeve which is connected to the jacket leg and a first stage sleeve projecting coaxially from the second stage sleeve. First and second stage locking profiles are presented inside the first and second stage sleeves, respectively. The first stage sleeve is thus accessible for cutting operations, severing both the first stage sleeve with the first pile-to-pile sleeve connection inside and the connected pile section within. This allows retrieval of the platform jacket, but preserves a second stage pile sleeve for re-deployment. Another aspect of the present invention is an improved pile sleeve adapted to facilitate reuse.

Claims

1. A reusable jacket base for an offshore platform of a configuration suitable to secure to an ocean floor upon installation with a plurality of piles, the jacket base comprising:

a plurality of jacket legs;

framework interconnecting the jacket legs; and

a plurality of pile sleeves connected to the jacket legs, the pile sleeves comprising;

a vertically extended, open-ended cylindrical member having a second stage sleeve which is connected to the jacket leg and a first stage sleeve projecting coaxially from the second stage sleeve;

a first stage locking profile inside the first stage sleeve; and

a second stage locking profile inside the second stage sleeve.

2. A reusable jacket base in accordance with claim 1 wherein the first and second stage locking profiles are each at least one annular groove in the interior wall of the cylindrical member whereby the first and second stage locking profiles are configured to receive an extrusion from one of the piles inserted therethrough at installation to form a secure connection.

3. A reusable jacket section in accordance with claim 1 wherein the first and second stage locking profiles are annular surfaces capable of sustaining a secure, grouted pile sleeve-to-pile sleeve connection, the jacket section further comprising:

an annular recess in the cylindrical member separating the first and second stage sleeves;

a packer installed in the annular recess disposed to selectively deploy a seal between the cylindrical member of the pile sleeves and the pile to isolate the first stage sleeve from the second stage sleeve during initial deployment of the jacket section;

an actuating fluid conduit in communication with the packer; and

a grout placement valve providing access to the interior of the first stage pile sleeve.

4. In an improved pile sleeve adapted to receive a pile in a securely connected relationship and having an extending cylindrical member and a first locking profile on the interior wall of the cylindrical member, the improvement comprising:

a second locking profile on the interior wall of the cylindrical member spaced apart from the first locking profile such that the pile may be hydraulically extruded into the first locking profile upon a first deployment of the offshore platform jacket, a portion of the pile sleeve and concentric pile at this first locking profile being accessible for removal to conveniently retrieve the offshore jacket for re-deployment to another location using the second locking profile.

5. An improved pile sleeve in accordance with claim 4 wherein said first and second locking profiles are each at least one annular groove in the interior wall of the cylindrical member whereby the first and second stage locking profiles are configured to receive an extrusion from one of the piles inserted therethrough at installation to form a secure connection.

6. An improved pile sleeve in accordance with claim 4 wherein the first and second stage locking profiles are annular surfaces capable of sustaining a secure, grouted pile sleeve-to-pile sleeve connection, the improved pile sleeve further comprising:

an annular recess in the cylindrical member separating the first and second stage sleeves;

a packer installed in the annular recess disposed to selectively and sealingly deploy between the cylindrical member of the pile sleeves and the pile to isolate the first stage sleeve from the second stage sleeve during initial deployment of the jacket section;

an actuating fluid conduit in communication with the packer; and

a grout placement valve providing access to the interior of the first stage pile sleeve.

7. A method for connecting a pile to a pile sleeve in the foundation of an offshore platform jacket, comprising:

setting the pile into an ocean floor through the pile sleeve;

isolating a first stage of a pile-to-pile sleeve interconnection which is presented in an extension of the pile sleeve from a second stage of the pile sleeve suitable to secure a pile-to-pile sleeve interconnection; and

securing the pile to the pile sleeve at the first stage during a first deployment of the offshore platform jacket;

whereby the second stage is reserved and conveniently available for a pile-to-pile sleeve interconnection should the offshore platform jacket be salvaged and redeployed;

retrieving the offshore platform jacket upon depletion of hydrocarbon reserves at the initial site, comprising;

cutting the concentric pile and pile sleeve anal removing the extension of the pile sleeve containing the first stage of pile-to-pile sleeve interconnection; and

raising the offshore platform jacket and rigging for transport; and

redeploying the offshore platform jacket.

8. A method in accordance with claim 7 wherein isolating the first stage from the second stage comprises:

inserting a locking tool into the pile; and

securing hydraulic seals in the pile above and below the level of a first locking profile in the first stage of the pile sleeve, but at a level not aligned with a second stage locking profile; and

wherein securing the pile to the pile sleeve comprises extruding the walls of the pile into the first locking profile with hydraulic pressure provided by the locking tool.

9. A method in accordance with claim 7 wherein isolating the first stage from the second stage comprises:

setting a packer in the annulus between pile and the pile sleeve at a level between the first and second stage sleeves; and

wherein securing the pile to the pile sleeve comprises injecting and setting grout in the annulus of the first stage sleeve between the pile and the pile sleeve.

10. A method for reusing an offshore platform jacket, comprising:

initially installing the offshore platform jacket, comprising;

setting the offshore platform jacket onto the seafloor at site;

securing piles into the seafloor through pile sleeves;

inserting a locking tool into the pile and securing hydraulic seals above and below a first locking profile presented on the interior of the pile sleeve, but isolated from a second locking profile on the interior of the pile sleeve;

extruding the walls of the pile into the first locking profile with hydraulic pressure provided by the locking tool; and

depressurizing and removing the locking tool; and

retrieving the offshore platform jacket upon depletion of hydrocarbon reserves at the initial site, comprising;

retrieving topside facilities from the offshore platform jacket;

cutting the concentric pile and pile sleeve and removing the extension of the pile sleeve containing the first locking profile; and

raising the offshore platform jacket and rigging for transport; and

redeploying the offshore platform jacket, comprising;

setting the offshore platform jacket onto the seafloor at a second site;

securing piles into the seafloor through pile sleeves;

inserting a locking tool into the pile and securing hydraulic seals above and below the second locking profile presented on the interior of the pile sleeve;

extruding the walls of the pile into the second locking profile with hydraulic pressure provided by the locking tool; and

depressurizing and removing the locking tool.

11. A method for connecting a pile to a pile sleeve in the foundation of an offshore platform jacket, comprising:

setting the pile into an ocean floor through the pile sleeve;

isolating a first stage of a pile-to-pile sleeve interconnection from a second stage;

comprising;

inserting a locking tool into the pile;

securing hydraulic seals in the pile above and below the level of a first locking profile in the first stage of the pile sleeve, but at a level not aligned with a second stage locking profile; and

securing the pile to the pile sleeve at the first stage comprising extruding the walls of the pile into the first locking profile with hydraulic pressure provided by the locking tool.