Offshore and subsea decommissioning will increase in the next five years or so as many producing fields are matured and cease production while the oil price continues to remain low. This emphasizes the need for a thorough decommissioning plan to ensure a safe and technically feasible solution while it is economically viable and safeguards the environment. Offshore and subsea decommissioning is commonly considered on a case-by-case basis using the Comparative Assessment (CA) process in which the best decommissioning solution is obtained. Health, Safety and Environmental (HSE) considerations are always paramount in any decommissioning process. The aim is to significantly reduce the long term risks to other benefactors of the sea while the associated short term risks to those responsible for decommissioning operations are minimized. A major part of any decommissioning project is subsea pipelines decommissioning (by “pipelines”, it is meant to include flowlines, trunklines and flexible too). There are a number of techniques available for decommissioning of subsea pipelines ranging from preservation for potential future use to full recovery or leaving in-situ. However, each subsea pipeline decommissioning technique should be considered on its own merit. Selection of each decommissioning technique depends on many parameters, inter alia, size of pipeline, type of pipeline (e.g. single pipe, pipe-in-pipe, piggyback), type of conveying fluid, operational environment (location), production history, Inspection, Repair and Maintenance (IRM) records, HSE considerations, connection to other facilities, technical feasibility (including potential use of advanced technologies), regulatory authorities requirements and socio-economic considerations. This paper will look at specifics of subsea pipelines decommissioning. It will examine the procedures to be undertaken from desk top activities (e.g. planning and CA) up to operational activities (e.g. pigging, flushing, cleaning, removal or leaving in-situ). Different scenarios are discussed and potential advantages and disadvantages of each scenario are presented. In addition, a guide is proposed for future pipelines decommissioning projects to follow a rational approach.
The domestic demand of gas is increasing in Brazil. Petrobras is responding to this challenge by bringing several gas fields on stream offshore Brazil. Among them is the Canapu field, located east of the State of Espirito Santo, about 75 km off the coast, in a water depth of 1608 m. The produced gas is transported using a 20 km long pipe-in-pipe (PIP) system to the Cidade de Vitoria floating, production, storage and offloading system (FPSO) located in the Golfinho field to be processed and then exported onshore through an existing gas pipeline.Technip was awarded an engineering, procurement, construction and installation (EPCI) contract and was responsible for the detailed design and installation of the first ever reeled PIP system offshore Brazil. The project was awarded on a fasttrack basis, which required design, qualification, fabrication and installation of the PIP system in less than 18 months. The scope also included two pipeline end terminations (PLET) with seven gate valves, free span rectification, the crossing of three flexible flowlines, and, pre-commissioning activities (flooding, cleaning, gauging and hydrotesting). The PIP system was also prone to lateral buckling, which required definition of a robust mitigation strategy.The design requirements for the Canapu PIP system involved the design and qualification of several technically advanced components and novelties in PIP design including the application of the first ever reelable mechanically clamped waterstop system and the use of buoyancy modules for lateral buckling management on a PIP system. This paper presents the overview of the design, fabrication and installation of Canapu PIP system as well as a summary of the qualification test program performed for the different PIP system components.
Prevention and arresting buckle propagation under high external hydrostatic pressure is a necessity for the deepwater rigid pipelines during installation and operation. The local compromise in geometric integrity will propagate at a high velocity, flattening the pipeline until it encounters a physical barrier that arrests the buckle. Traditionally, external clamp-on type buckle arrestors are considered by the pipeline designers for rigid pipelines that are installed by reeling method. Integral Buckle Arrestors (IBAs) could provide a more reliable method of arresting the propagating buckle during installation and subsequent design life. However, design and installation of integral buckle arrestors for rigid reeled pipeline installation would be a challenge. IBA is fabricated from a thick walled pipe section with the same inner / outer diameter as that of pipeline and wall thickness transition to match the thickness of the pipe towards the ends. For the reeled pipelines, additional cost economies will be achieved by the use of IBAs which allow continuous installation by reel lay vessel without interruptions. This paper gives background information, design and installation considerations and practical issues in the fabrication of IBAs. Recent Subsea7 experiences in design and installation of IBAs will be also addressed in this paper. This paper does not cover the aspects to be taken into consideration, if the buckle arrestor is also serving dual purpose as a J-lay support collar.
Reeling is a fast, reliable and cost effective method for installing subsea flowline systems up to 20 inch in diameter. The individual flowline joints are lined up and welded together onshore to make long stalks of pipe before being spooled onto the large reels of reel lay vessels. On arrival in the field offshore, it is spooled off, straightened and laid on the seabed up to 10 times faster than conventional S-lay or J-lay methods. The ability to carry out the fabrication and welding onshore, off-line from the vessel critical path, allows very high quality welding and coating to be achieved. Over the last few years, it is evident that the engineering fundamentals, mechanics and cost effectiveness of the reeling process are now well understood within different quarters of the offshore industry as many major pipelaying Contractors own, or are planning to own, a reel lay vessel. What is apparently missing, however, is the implications and practical aspects of the reeling process when it comes to implementation during project execution. This paper reviews the engineering fundamentals of the reeling process first and then discusses the practical aspects and applications of reeling mechanics from spoolbase fabrication to spooling-on process up to the offshore campaign and spooling-off process and subsea installation.
The domestic demand of gas is increasing in Brazil. Petrobras is responding to this challenge by bringing several gas fields on stream offshore Brazil. Among them is the Canapu field, located east of the State of Espirito Santo, about 75 km off the coast, in a water depth of 1608 m. The produced gas is transported using a 20 km long pipe-in-pipe (PIP) system to the Cidade de Vitoria floating, production, storage and offloading system (FPSO) located in the Golfinho field to be processed and then exported onshore through an existing gas pipeline.Technip was awarded an engineering, procurement, construction and installation (EPCI) contract and was responsible for the detailed design and installation of the first ever reeled PIP system offshore Brazil. The project was awarded on a fasttrack basis, which required design, qualification, fabrication and installation of the PIP system in less than 18 months. The scope also included two pipeline end terminations (PLET) with seven gate valves, free span rectification, the crossing of three flexible flowlines, and, pre-commissioning activities (flooding, cleaning, gauging and hydrotesting). The PIP system was also prone to lateral buckling, which required definition of a robust mitigation strategy.The design requirements for the Canapu PIP system involved the design and qualification of several technically advanced components and novelties in PIP design including the application of the first ever reelable mechanically clamped waterstop system and the use of buoyancy modules for lateral buckling management on a PIP system. This paper presents the overview of the design, fabrication and installation of Canapu PIP system as well as a summary of the qualification test program performed for the different PIP system components.
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