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BR-102024017661-A2 - METHOD OF SUBMARINE CONNECTION OF ANCHORING LINES UNDER TRACTION

BR102024017661A2BR 102024017661 A2BR102024017661 A2BR 102024017661A2BR-102024017661-A2

Abstract

The present invention is applied in the area of mooring line maintenance and, more particularly, relates to a method of underwater connection of mooring lines under tension comprising: installing, by means of an ROV (31) of a supporting AHTS vessel (3), one or more floats (43) on an anchor hook shackle (42) of a fixed point mooring line (41); providing, by means of a main AHTS vessel (2), a handling line (20) comprising a handling cable (21) fixed to the main AHTS vessel (2) and a ballast mooring line (22) connected to the handling cable (21); connecting, by means of the ROV (31), the ballast mooring line (22) to a link of a bottom mooring line (12) of a UEP (1) in the vicinity of the mooring hook (13); To pay into the water, by means of the main AHTS vessel (2), the handling line (20) with the ballast mooring line (22) connected to the bottom mooring link (12) in the vicinity of the anchor hook (13); move the main AHTS vessel (2) towards a fixed anchor point (4), passing by it, until reaching a desired position; connect, by means of the ROV (31), the anchor hook (13) to the anchor hook shackle (42); and disconnect, by means of the ROV (31), the ballast mooring line (22) from the bottom mooring link (12). The present invention also relates to other methods of underwater connection of mooring lines under tension.

Inventors

  • LEIZ NUNES PEREIRA DA SILVA
  • RODRIGO ALVES PONS
  • ELEANDRO MEIRA DE OLIVEIRA

Assignees

  • Petróleo Brasileiro S.A. - Petrobras

Dates

Publication Date
20260310
Application Date
20240828

Claims (18)

  1. 1. Subsea mooring line connection method under tension characterized in that it comprises: installing, by means of an ROV (31) of a supporting AHTS vessel (3), one or more floats (43) on an anchor hook shackle (42) of a fixed point mooring line (41); providing, by means of a main AHTS vessel (2), a handling line (20) comprising a handling cable (21) fixed to the main AHTS vessel (2) and a ballast mooring line (22) connected to the handling cable (21); connecting, by means of the ROV (31), the ballast mooring line (22) to a link of a bottom mooring line (12) of a UEP (1) in the vicinity of the anchor hook (13); pay into the water, by means of the main AHTS vessel (2), the handling line (20) with the ballast mooring line (22) connected to the bottom mooring link (12) in the vicinity of the anchor hook (13); move the main AHTS vessel (2) towards a fixed anchor point (4), passing by it, until it reaches a desired position; connect, by means of the ROV (31), the anchor hook (13) to the anchor hook shackle (42); and disconnect, by means of the ROV (31), the ballast mooring line (22) from the bottom mooring link (12).
  2. 2. Method according to claim 1, characterized in that the weight of the ballast mooring (22) varies between approximately 30% and approximately 60% of the ideal tension of the anchor line (10).
  3. 3. Method, according to claim 2, characterized in that for a catenary type of anchorage the weight of the ballast tether (22) is preferably closer to 30% of the ideal tension, and for a taut-leg type of anchorage the weight of the ballast tether (22) is preferably closer to 60% of the ideal tension.
  4. 4. Method, according to any of the preceding claims, characterized in that the handling cable (21) is made of steel, synthetic fiber, or a combination thereof.
  5. 5. Method, according to any of the preceding claims, characterized in that the ballast mooring (22) is connected to the bottom mooring link (12) in the vicinity of the anchor hook (13) by a connecting means selected from: a grappling hook, a sling, or a load strap.
  6. 6. Method, according to any of the preceding claims, characterized in that it further comprises connecting a guide cable to the end of the anchor hook (13) for handling the ROV (31).
  7. 7. Method, according to any of the preceding claims, characterized in that the desired position of the main AHTS vessel (2) is equivalent to a position in which a total length of handling line (20) is approximately 150% of the total length of the mooring line (10) or of the mooring line (10) together with the fixed point mooring (41).
  8. 8. Method, according to any of the preceding claims, characterized in that it further comprises, after the step of moving the main AHTS vessel (2) to a desired position, applying propulsive force, by means of the main AHTS vessel (2), until the mooring hook (13) is close enough to the mooring hook shackle (42).
  9. 9. Method, according to any of the preceding claims, characterized in that the anchor hook (13) is a KS hook.
  10. 10. Subsea mooring line connection method under tension characterized in that it comprises: connecting, by means of an ROV (81) of a supporting AHTS vessel (8), a working cable (82) lowered by the supporting AHTS vessel (8) to a link of a fixed point mooring line (91) from a fixed point mooring line (9) in the vicinity of a mooring hook shackle (92); providing, by means of a main AHTS vessel (6), a handling line (60) comprising a handling cable (61) fixed to the main AHTS vessel (6) and a ballast mooring line (62) connected to the handling cable (61); connecting, by means of the ROV (81), the ballast mooring line (62) to a link of a bottom mooring line (52) of a UEP (5) in the vicinity of the mooring hook (53); pay into the water, by means of the main AHTS vessel (6), the handling line (60) with the ballast mooring line (62) connected to the bottom mooring link (12) in the vicinity of the anchor hook (13); move the main AHTS vessel (6) towards the fixed anchor point (9), passing by it, until it reaches a desired position; pay in, by means of a secondary AHTS vessel (7), a handling line (70), containing handling cable (71) and ballast mooring line (72); connect, by means of the ROV (81), the handling line (70) of the secondary AHTS vessel (7) to a link of the fixed point mooring line (91) in the vicinity of the anchor hook shackle (92); move the secondary AHTS vessel (7) towards the UEP (5), applying propulsive force equivalent to the horizontal force to be exerted by the UEP's (5) mooring line (50) after its connection to the fixed point mooring (91), until the mooring hook shackle (92) is close to its working depth; connect, by means of the ROV (81), the mooring hook (53) to the mooring hook shackle (92); disconnect, by means of the ROV (81), the ballast mooring (62) of the main AHTS vessel (6) from the bottom mooring link (52) and the ballast mooring (72) of the secondary AHTS vessel (7) from the fixed point mooring link (91).
  11. 11. Method according to claim 10, characterized in that the connection between the working cable (82) and the link of the fixed point mooring (91) is made by a connection means selected from: a grappling hook, a sling, or a load strap.
  12. 12. Method, according to claim 10 or 11, characterized in that the weight of the ballast mooring line (62) varies between approximately 30% and approximately 60% of the ideal tension of the mooring line (50).
  13. 13. Method according to claim 12, characterized in that for a catenary type of anchorage the weight of the ballast tether (62) is preferably closer to 30% of the ideal tension, and for a taut-leg type of anchorage the weight of the ballast tether (62) is preferably closer to 60% of the ideal tension.
  14. 14. Method, according to any one of claims 10 to 13, characterized in that the ballast mooring (62) is connected to the bottom mooring link (52) in the vicinity of the anchor hook (53) by a connecting means selected from: a grappling hook, a sling, or a load strap.
  15. 15. Method, according to any one of claims 10 to 14, characterized in that it further comprises connecting a guide cable to the end of the anchor hook (53) for handling the ROV (81).
  16. 16. Method, according to any one of claims 10 to 15, characterized in that the desired position of the main AHTS vessel (6) is equivalent to a position in which a total length of handling line (60) is approximately 150% of the total length of the mooring line (50) or of the mooring line (50) together with the fixed point mooring (91).
  17. 17. Method, according to any one of claims 10 to 16, characterized in that it further comprises, after the step of moving the main AHTS vessel (6) to a desired position, applying propulsive force, by means of the main AHTS vessel (6), exerting force approximately equal to the final traction of the UEP mooring line (5), leaving the mooring hook (53) close enough to the mooring hook shackle (92).
  18. 18. Method, according to any one of claims 10 to 17, characterized in that the anchor hook (53) is a KS hook.

Description

Field of invention [001] The present invention is applied in the area of mooring line maintenance and, more particularly, relates to methods of underwater connection of mooring lines under tension, without the use of a winch on the stationary production unit (SPU). Fundamentals of the invention [002] An anchoring (or mooring) system comprises various pieces of equipment that hold a stationary unit in place against the forces of waves, wind, and currents. Thus, an anchoring system plays a fundamental role in the oil and gas industry, which is to support the safe operation of stationary units that produce oil and gas offshore. Stationary units are anchored by mooring systems in a wide range of water depths, from shallow levels such as 20 meters to depths such as 2,000 meters or more. [003] There are many different types of anchoring systems, from which the most appropriate system for a given unit is selected to match the environmental conditions. [004] For example, in monsoon regions, a “turret” mounted on the outer bow is often used. In shallow waters, an anchoring system called “Tower Yoke” may be used. In areas where sea conditions are moderate, a catenary anchor leg mooring (CALM) float system, which is used for loading and unloading tankers in the Gulf, is used, or a multipoint anchoring system called “Spread Mooring”, in which several anchor lines are used to directly secure the unit without a “turret” system. [005] Regardless of the type and configuration of the anchoring system, for the installation of new anchor lines, or even for the reinstallation of sections in broken lines, it is common to use the UEP's own winch to lift and/or support the line sections, or to handle them during the connection operation with other sections and adjust the traction at the end of the process. [006] However, there may be situations in which it is not possible to use the UEP winch, for example, when the unit is not ready to respond to emergency operations (such as a line break) due to a mechanical problem with the anchoring winches or due to sanitary restrictions, as was the case with the restrictions resulting from the COVID-19 pandemic. [007] In these cases, it becomes necessary to develop a method for connecting underwater mooring lines, for the recomposition of the mooring system, without the use of winches on board the UEPs. State of the Art [008] The state of the art shows some documents that reveal matters within the technological field of the present invention. [009] Document EP1318072A2 discloses a floating platform that has a mooring cable that passes through a coupling device tied to the suction anchor. The coupling device allows adjusting the effective length of the mooring cable between the platform and the anchor by means of a vessel independent of the platform. The vessel pulls the mooring cable through the coupling device, reducing the effective length of the mooring cable, until the floating platform is in the desired position. The coupling device includes a locking device to prevent the effective length of the mooring cable from changing when the floating platform is in the desired position. [010] In the aforementioned document EP1318072A2, the mechanism used to adjust the tensions in the mooring/anchoring cable is a coupling device, which is connected to a working cable of the vessel and positioned close to the anchor. This mechanism is employed by only one vessel, without the use of other vessels to assist in the correct positioning (distance adjustment) and distribution of applied loads, as is the case with the present invention. Furthermore, this document does not reveal or suggest a method for replacing sections of the mooring line that may have broken, carrying out all the steps that include fishing and the sub-processes of preparing, arranging, and handling the sections between the different vessels. [011] In turn, document PI0204708-0B1 discloses a quick anchoring apparatus which allows for the underwater connection and disconnection of mooring lines to mooring devices already fixed to the seabed. The quick anchoring apparatus comprises mooring lines, cables, hooks and floats specifically arranged and fitted which, fixed to the submerged end of the mooring line, enable a single support vessel, together with a remotely operated vehicle, to carry out the entire mooring operation of a floating platform's mooring line. The document also refers to a method for installing and uninstalling the quick anchoring apparatus. [012] However, in document PI0204708-0B1 the mooring line is reconnected to the floating structure at the end of the process, so that it can be connected to the tensioning devices on the floating structure. That is, the winches on the floating structure are still used to provide the desired tension to the line. PI0204708-0B1 does not reveal or suggest the use of two or more different UEP vessels to handle the line sections, assemble new sections, and the entire positioning and tracti