Pulling Structures into Water

Patent metadata

Field	Value
Publication number	US-2023182868-A1
Application number	US-202117922158-A
Country	US
Kind code	A1
Filing date	Apr 28, 2021
Priority date	Apr 29, 2020
Publication date	Jun 15, 2023
Grant date	—

Abstract

A structure such as a pipeline bundle is pulled into or through shallow water, for example when launching the structure, by applying a tensile pulling force to the structure through rigging that extends to the structure from a winch of a first vessel. The pulling force is at least partially reacted through a pennant line that extends from the first vessel to a second vessel and that hangs between the first and second vessels to engage the seabed soil frictionally. The vessels may also self-propel to contribute their thrust to the pulling force. The pennant line includes a clump weight such as a bundle of chains that can be repositioned easily for additional pulls by being lifted between the vessels before being lowered to the seabed at a new location.

First claim

1 . A method of pulling a structure into or through water, the method comprising:
applying a tensile pulling force to the structure through rigging that extends to the structure from a first vessel; and reacting the pulling force through a pennant line that extends from the first vessel to a second vessel and that frictionally engages seabed soil between the first and second vessels.

2 . The method of claim 1 , comprising frictionally engaging the seabed soil with at least one clump weight of the pennant line.

3 . The method of claim 2 , wherein the or each clump weight comprises two or more chains attached to, or in series with, the pennant line.

4 . The method of any preceding claim , comprising also reacting the pulling force by propelling the first and/or second vessels away from the structure.

5 . The method of claim 4 , comprising imparting tension in the pennant line by propelling the second vessel away from the structure.

6 . The method of claim 5 , comprising resisting movement of the pennant line toward the structure by propelling the second vessel away from the structure.

7 . The method of claim 6 , comprising moving the pennant line away from the structure by propelling the second vessel away from the structure.

8 . The method of any preceding claim , comprising resisting movement of the pennant line toward the structure by engaging the seabed with an anchor of the pennant line.

9 . The method of any preceding claim , comprising operating a winch aboard the first vessel to apply the pulling force to the structure.

10 . The method of any preceding claim , further comprising:
relaxing the pulling force applied to the structure through the rigging; lifting the pennant line to reduce or to interrupt frictional engagement with the seabed soil; moving the first and second vessels and the pennant line away from the structure; lowering the pennant line to increase or to resume frictional engagement with the seabed soil; and reapplying the pulling force to the structure through the rigging.

11 . The method of claim 10 , comprising lifting substantially all of the pennant line clear of the seabed soil.

12 . The method of claim 10 or claim 11 , comprising lifting at least a portion of the pennant line onto the second vessel.

13 . The method of claim 12 , comprising moving the second vessel toward the first vessel for lifting the pennant line.

14 . The method of any of claims 10 to 13 , comprising keeping the pennant line coupled to the first and second vessels while lifting, moving and lowering the pennant line.

15 . The method of any of claims 10 to 14 , comprising paying out the rigging from the first vessel while moving the first vessel away from the structure.

16 . The method of any of claims 10 to 15 , comprising keeping the rigging coupled to the structure and the first vessel while moving the first vessel away from the structure.

17 . The method of any preceding claim , comprising floating the rigging on water between the first vessel and the structure.

18 . The method of any preceding claim , comprising suspending respective ends of the pennant line from the vessels in a catenary configuration.

19 . The method of any preceding claim , wherein the first vessel is located in shallower water than the second vessel.

20 . The method of any preceding claim , employed when pulling the structure across a shore and into water, wherein the first vessel is a near-shore tug and the second vessel is a far-shore tug.

21 . A pulling arrangement for pulling a structure into or through water, the arrangement comprising:
first and second towing vessels disposed in series with each other and with the structure; rigging that extends to the structure from the first vessel; and a pennant line that extends from the first vessel to the second vessel and that frictionally engages seabed soil between the first and second vessels.

22 . The arrangement of claim 21 , wherein the rigging extends to the structure from a winch of the first vessel.

23 . The arrangement of claim 20 or claim 21 , wherein the pennant line comprises at least one clump weight.

24 . The arrangement of claim 23 , wherein the or each clump weight comprises two or more chains attached to, or in series with, the pennant line.

25 . The arrangement of any of claims 21 to 24 , wherein the pennant line comprises at least one contingency anchor that is arranged to bury itself into the seabed soil in the event of longitudinal movement of the pennant line toward the structure.

26 . The arrangement of claim 25 , wherein the or each contingency anchor is arranged to disengage from the seabed soil in the event of longitudinal movement of the pennant line away from the structure.

27 . The arrangement of any of claims 21 to 26 , wherein the pennant line is coupled to a winch of the second vessel.

28 . The arrangement of any of claims 21 to 27 , wherein the rigging is positively buoyant.

29 . The arrangement of any of claims 21 to 28 , wherein the first vessel is located in shallower water than the second vessel.

30 . The arrangement of any of claims 21 to 29 , wherein the structure is at a shore location, the first vessel is a near-shore tug and the second vessel is a far-shore tug.

Assignees

• Subsea 7 Ltd

Inventors

• Joensen Arnbjorn
• Ogbodo Nwabueze Samuel

Classifications

• B63B21/62 Primary

  characterised by moving of more than one vessel (rigid interconnections between pontoons B63B35/38) · CPC title

• B63B21/66 Primary

  Equipment specially adapted for towing underwater objects or vessels, e.g. fairings for tow-cables ({paravanes for dragging fishing nets A01K73/02; } salvaging underwater vessels or objects B63C7/00; towed underwater vessels B63G8/42) · CPC title

• F16L1/165

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

• B63B21/56 Primary

  Towing or pushing equipment (tugs B63B35/66; towing arrangements for water sports use B63B34/60) · CPC title