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TechnipFMC’s ETH Blanket Offers Reliable Subsea Solutions

Breakthrough System Provides Efficient Method for Unplugging Flowlines

Hydrocarbon production from subsea wells is a complex endeavor. One potential problem is
that flowlines can be plugged – or blocked – by hydrates or wax. This can lead to a costly production shutdown and unreliable remedial work.

Resolving this problem hasn’t been easy. Remedies are invasive and expensive and offer no guarantee of success. The expenditures associated with subsea flowline unplugging can increase quickly with loss of production and the investigations needed to identify the best remediation strategy. Such investigations cover identification of the plug's nature, its location, assessment of the dissociation method and flowline restart strategy.

In some scenarios, the plug dissociation method, like depressurizing for hydrate plugs and chemical soaking or pigging for paraffin wax plugs, may take several days to several months. Often, the remediation cannot be performed from the topside facility, requiring the mobilization of a drillship vessel to carry over manifold or tree work. Ultimately, the plug removal method may fail and lead to flowline replacement or abandonment.

Heating the plugged flowline to the point where the plug dissociates is one of the solutions, but this poses a considerable challenge. TechnipFMC has developed expertise over the past few years in active heating technologies. However, until recently, these technologies were applicable to new developments only and represented capital and operating expenditures.

Now, a TechnipFMC development is set to be transformational, providing an efficient and reliable system to address unplanned plugging in a cost-effective way. The Electrically Trace Heated (ETH) Blanket is a compact and modular system with a length of several hundred meters that can be deployed onto any existing flowline (flexible or rigid) in any condition (buried or not) from a light construction vessel within a short mobilization period of about two weeks. The system is equipped with trace heating cables capable of heating the flowline and dissociating the plug. It also incorporates distributed temperature sensing (DTS) to monitor the flowline’s bore temperature to identify the location of the plug, characterize its nature and follow up the temperature and pressure profiles to dissociate the plug in a controlled manner.

ETH Blanket

Components of the ETH Blanket

The development of the ETH Blanket involved teams from across TechnipFMC, from flow assurance and ETH technologies to mechanical design and installation, combining the skills and knowledge of experts throughout the subsea business.


TechnipFMC has a long history in ETH technology, but previous products, while effective, could not be retrofitted around existing pipelines until today. The new ETH Blanket is stored on a reel on the deck of a light construction vessel and typically measures 250 meters (821 feet) long and three meters (10 feet) wide. The blanket is deployed on the plugged flowline and heated. It is then recovered once the job is done.

ETH Blanket

Lower section of ETH Blanket prototype with heat trace and optical cables

The ETH blanket is designed to be cost-effective and reliable, leading the competition in providing client assurances that flowlines will be unplugged within a given time and operating expenses reduced. Representing a step change for the subsea industry, the service provides an alternative, efficient and predictable intervention system to disassociate hydrate plugs in subsea flowlines using active heating.