Active heating of subsea flowlines is an attractive solution for facing flow assurance issues related to always going deeper and longer, as well as more complex fluids and critical wellhead flowing conditions (pressure, temperature, flowrate) prone to pour point issues, hydrates and/or wax appearance risk. Over the last 15 years, several active heating technologies have been developed and operated in order to significantly help solve flow assurance issues from the subsea wellheads up to the surface support facilities. These technologies have demonstrated to be very different in their design and operability (use of hot water, direct or indirect electrical heating) but also in their efficiency and cost. In parallel with the development of heated flexible pipe designated IPB (Integrated Production Bundle) already used for field development in West Africa and Brazil as well as a rigid heated pipe-in-pipe technology, both using electrical heat trace cables, Technip has been involved in the design, construction and installation on several projects of all active heating technologies. Based on this extensive knowledge and track-record, this paper describes and compares the working principle as well as the advantages and drawbacks of the different active heating technologies. This paper also identifies their limitations with regards to field application, i.e. length and water depth based on their actual development status. On the basis of different generic case studies (shallow long tie-back, shallow in-field development, deep water tie-back and ultra-deep water in-field development), this paper finally reviews all the potential benefits the different active heating technologies can bring to a project and includes an economical comparison of these technologies.

Subsea Flowlines blockage due to hydrate or paraffin plugs, resulting from pour point issues or deposition, is a frequent concern in subsea production requiring expensive remediation methods. The expenditures associated with subsea flowlines unplugging can increase very quickly, especially when considering the associated loss of production as well as the various investigations needed to define the appropriate remediation strategy. Such investigations cover the identification of the plug's nature, its location, the assessment of the appropriate dissociation method as well as the flowline restart strategy. In some scenarios, the plug dissociation method, like depressurization for hydrate plug and chemical soaking or pigging for paraffin plug, may take a long time ranging from several days to several months. Often, the remediation cannot be performed from the topside facility and will require the mobilization of an external drillship vessel to carry manifold or Xmas tree work over. Ultimately, the plug removal method may fail and therefore lead to flowline abandonment and/or replacement. From these observations, there is room for the development of a more efficient, predictable and reliable method to unplug subsea flowlines. With this regard, the development a new subsea flowline intervention system named Electrically Trace Heated Blanket (ETH Blanket) has been initiated. The ETH-Blanket is a compact and modular system, with length adaptable typically up to 2km. The system is equipped with trace heating cables relying on Joule's Effect for heat generation to dissociate the plug and distributed temperature sensing (DTS) to monitor the flowline's bore temperature in order to identify the location of the plug, characterize its nature and follow-up the temperature and pressure profiles during plug dissociation. The ETH Blanket can be deployed onto any kind of existing flowlines (flexible or rigid) and in any condition (buried or not) from a Light Construction Vessel. The power required to dissociate the plug is low (typically <1MW) and once the dissociation is completed, the ETH Blanket can be recovered onto the intervention vessel and relocated. This paper describes into details the ETH-Blanket assembly and its operating principles, its anticipated thermal performances determined using CFD modeling, as well as and its deployment method and spread. To illustrate the ETH-Blanket efficiency, a typical multiple hydrate plugs dissociation operation will be presented and compared to a conventional topside depressurization. As a conclusion, the on-going fast-track qualification programme for the development of the Electrically Trace Heated Blanket Technology will be presented.

This paper provides an overview of the work completed to design, qualify, manufacture and integrate electrical and optical double barrier penetrators with the Electrically Trace Heated Pipe-in-Pipe (ETH-PiP) as part of the Neptune Energy Fenja Development Project. Typical subsea penetrator systems in the oil and gas industry, such as pumps, compressors and X-trees are designed to be retrievable, to enable periodic refurbishment as well as providing the option for replacement, if required. However, the ETH-PiP architecture makes retrieval of system components complicated and uneconomical. Both the electrical and optical dual barrier penetrator system designs have to comply with a set of ETH-PiP specific criteria, such as to be maintenance free over a 25 years service life, prevent water ingress to the pipeline, provide pressure containment for operational media (in an unlikely scenario where the inner pipe bursts) and guarantee minimum footprint to allow an optimum integration onto the Pipeline End Termination (PLET) structure. In addition, the electrical system has to comply with a medium voltage rating (i.e. 5.0/8.7kV) to ensure a wide range of possible ETH-PiP architectures. The optical system has to maintain insertion loss below 0.5dB and a back reflection below -45dB to comply with the stringent requirements of distributed temperature monitoring sensor system over long distances. The qualification program of the electrical dual barrier penetrator system was performed in accordance with IEC 60502-4 and SEPS-SP-1001. A tailor made sequence had to be developed for the optical system, based on guidance from SEAFOM-TSD-01, considering that the system partly falls outside the associated standard application. The electrical dual barrier penetrator system qualification sequence was developed in two phases; firstly, the electrical transition contacts in the feedthrough chamber were qualified in accordance with IEC 60502-4 and secondly, four electrical double barrier penetrator prototypes were manufactured to allow the completion of the qualification sequence defined as per SEPS-SP-1001. The optical dual barrier penetrator system qualification employed the manufacturing of three prototypes to execute the pre-defined qualification sequence. Following the individual qualification of the electrical and optical dual barrier penetrator systems, subsequent welding and full-scale assembly trials were performed to ensure that the maximum allowable temperatures within the penetrators would not be exceeded during welding to the PLET, and to proof test the assembly procedure. Electrical verification testing was also undertaken during these trials to verify that the integrity of the penetrators had been maintained during the assembly and that the PLET arrangement did not give rise to any electrical stresses that could result in excessive deterioration of the penetrators. Integration of the four electrical and two optical dual barrier penetrator systems to the project PLET was completed in Q1 2020, with the actual subsea installation of the first ETH-PiP section including the PLET in Q3 2020.

This paper presents the foundations as well as the main outcomes of the development, industrialization, fabrication and installation of the TechnipFMC's Electrically Trace Heated Pipe-in-Pipe (ETH-PiP) 2.0 for application on the Fenja field development. The Fenja Field is located offshore mid-Norway at a water depth of approximately 324m, and consists of two separate hydrocarbon accumulations, the Pil and Bue reservoirs, with fluid properties leading to flow assurance challenges such as hydrates and wax formation. Following successful deployment of a first generation of Electrically Trace Heated Pipe-in-Pipe on the TotalEnergies (then Total) Islay Field in 2011, TechnipFMC have conducted the development and industrialization of a completely new generation of ETH-PiP 2.0. The new ETH-PiP 2.0 has higher electrical rating of 3.8/6.6kV to overcome the specificities of the Fenja field development including the long tie-back distance of 36.8km which makes Fenja the longest (and largest) ETH-PiP in the world. Subsequent to successful qualification of the ETH-PiP system, TechnipFMC has completed the manufacturing of 36.8km of ETH-PiP stalks at the Evanton spoolbase. These were then loaded out onto the Deep Energy pipelay vessel for subsea installation by reel lay. The installation was finalized in summer 2021 with the complete system being connected and tested from the Njord A platform after it returned from refurbishment in spring 2022. This paper presents the qualification, industrialization, assembly and installation of the new generation ETH-PiP 2.0 which forms part of the Fenja field development.