EP-4737297-A1 - HYBRID MOORING SYSTEM

Abstract

Hybrid mooring system between a stationary production unit (SPU) and a fixed mooring point, wherein the SPU balcony comprises: at least one hydraulic power unit (HPU); at least one rotary winch (12); and one or more chain-stoppers equipped with an eyebolt. Furthermore, the hybrid mooring system has a mooring line comprising: a fixed mooring point (50); at least two bottom chain sections (30), one of which comprises a waiting shackle (32); a KS hook (34); an in-line tensioner (36); a sacrificial line (38); at least one main polyester cable (40); at least two mooring pigtails (42); a top chain line (44); and an end assembly connection (46).

Inventors

• ALVES PONS, Rodrigo

Assignees

• Petroleo Brasileiro S.A. - PETROBRAS

Dates

Publication Date

20260506

Application Date

20250917

Claims (9)

1. HYBRID MOORING SYSTEM BETWEEN A STATIONARY PRODUCTION UNIT (SPU) AND A FIXED MOORING POINT (50), characterized in that : the SPU balcony (1) comprises: at least one hydraulic power unit (HPU) (16); at least one rotary winch (12); and one or more chain-stoppers (10) equipped with a gantry (14) with an eyelet; the hybrid mooring system additionally features an mooring line (2) comprising: at least two bottom chain sections (30) connected to the fixed mooring point (50), wherein one of the bottom chain sections comprises a waiting shackle (32); a KS hook (34); an in-line tensioner (36); an active chain (52) followed by a sacrificial line (38); a main polyester cable (40); at least two chain tails (42); a top chain (44); and an end assembly connection (46).
2. SYSTEM, according to claim 1, characterized in that the gantry (14) with the chain-stopper eyelet (10), when in operation, is used to couple a pulley (18) to assist in moving the chain.
3. SYSTEM, according to claim 1, characterized in that the fixed mooring point (50) is one of: torpedo piles, suction piles, or vertical load anchors (VLA).
4. SYSTEM, according to claim 1, characterized in that the KS hook (34) is coupled underwater to the waiting shackle (32) of the fixed mooring point (50).
5. SYSTEM, according to claim 1, characterized in that the in-line tensioner (36) is positioned in the deepest section of the mooring line (2), below the polyester cables, to minimize the negative effect on the top angle of the mooring line (2).
6. SYSTEM, according to claim 1, characterized in that the sacrificial cable (38) is used to allow the mooring line (2) to be opened during maintenance or demobilization of the SPU.
7. SYSTEM, according to claim 1, characterized in that the top chain (44) is divided into two sections, allowing the AHTS to leave the first section mounted on the top polyester cable and deliver the second section to the SPU.
8. SYSTEM, according to claim 1, characterized in that the end assembly connection between the two sections of the top chain (44) is made on board the AHTS, before releasing the mooring line (2) into the water.
9. SYSTEM, according to claim 1, characterized in that the operation of the balcony (1) requires only the repositioning of the pulley and the winch cable to serve the next mooring line.

Description

FIELD OF THE INVENTION The present invention falls within the technical field of naval and offshore engineering, with an emphasis on mooring systems for floating oil production platforms (FPSO - Floating Production, Storage, and Offloading), as well as operations related to the maintenance, demobilization, and operation of such systems in challenging maritime conditions. BACKGROUND OF THE INVENTION Mooring systems onboard oil production platforms, commonly called mooring systems, have the function of moving the installation mooring outward (paying the chain), allowing the mooring line to be connected to the platform, and then retracting the installation chain and excess top chain until the mooring line reaches working tension. On modem FPSO platforms, the mooring system typically consists of a fairlead (a pulley that diverts the chain from its top angle to vertical), a chain-stopper (an articulated hydraulic device that "bites" the chain, locking it), and a chain-jack (a device responsible for effectively moving and applying tension to the chain, similar to a hydraulic jack). On a modem FPSO, the mooring lines are divided into four clusters, and accordingly, the mooring system of the FPSO is divided into four mooring balconies. A typical balcony consists of one chain-stopper per line and a pair of rails, which move the chain locker or box, and the chain-jack, which is attached to it. The four balconies are powered by two high-capacity hydraulic power units (HPUs), one located in the utility area of the FPSO and the other on the forecastle. The chain-jack and its HPU are designed to provide maximum pulls of between 400 and 600 tons-force. Although highly safe, current mooring systems are significantly complex and, therefore, subject to failures that lead to downtime during hook-up operations. Hook-up is the operation of connecting a new platform to its mooring system. In a typical hook-up operation, the AHTS (Anchor Handler and Tug Supply) vessel approaches the FPSO carrying the mooring line, receives a messenger cable from the FPSO, through which it pulls the installation chain, which is then connected to the mooring line and released into the water. Finally, the mooring winch of the FPSO retrieves the installation chain until the top chain can be set on the chain-stopper. Tensioning of the mooring lines usually occurs after hook-up. Maintaining this equipment during the operational life of the platform brings inherent challenges due to its complexity, and the operability of the mooring winch can become critical to the safety of the platform in the event of mooring line failure. Furthermore, the lack of operability of the mooring winch is a typical problem during mooring line maintenance and demobilization at the end of the service life of the unit. In recent years, some smaller platforms have been equipped with innovative technology that eliminates the need for a mooring winch and all its associated equipment. In this solution, the fairlead is replaced by an articulated universal joint (uni-joint), the mooring winch by a device consisting of a pulley similar to a fairlead, and a spring-loaded ratchet-like latch (in some models, opening and closing are performed by a ROV (Remotely Operated Vehicle - remotely operated underwater vehicle). In the mooring operation with the in-line tensioner, the first section of the top chain can be installed offshore or pre-installed at the shipyard. For typical Brazilian coastal conditions, a section of chain must be pre-installed at the shipyard. This section is connected to the uni-joint and temporarily accommodated on the side of the platform. The AHTS can then connect this chain directly (in shallow water) to the rest of the mooring line and release it into the water, or install an intermediate section (in deep water) and then connect this second section to the rest of the mooring line. However, the in-line tensioner impacts the mooring operations of a new platform (hook-up), such as chain accommodation and release. In deep water, it would be necessary to pre-install approximately 70 meters of chain per line, which may be impractical on a modem FPSO. Furthermore, there is no reliable method for replacing the chain connected to the uni-joint, which poses a significant risk to mooring system maintenance throughout the service life of the platform. Demobilization can also show similar difficulties to units with a non-operational winch. The invention solves the technical problem of optimizing both the mooring and demobilization processes of floating oil production platforms by combining features of a traditional mooring winch system and in-line tensioners to create a hybrid system that leverages the strengths of each. By utilizing a low-capacity rotary winch in conjunction with other devices, the invention allows for faster mooring operations compared to the system currently used on large FPSOs (the same features that make the chain-jack safe limit its speed). Additionally,