Portable Flowline Remediation System can halve daily operations costs

The Flowline Remediation System (FRS) can lower daily maintenance costs by more than 50%, to around $200,000 to $400,000, as it does not require rig rental and uses coiled tubing, Bin Xie, Project Engineer at Oceaneering, the FRS developer, said.

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The Flowline Remediation System is used for the hydrate remediation, or unblocking, of large volume flowlines on the seabed through mudmat-based equipment.

“The FRS is a modular equipment the size of a standard offshore box, 20 feet by 8 feet by 8 feet, hence able to be deployed and recovered from a light intervention vessel, class I,” Bin Xie told Upstream Intelligence.

While the cost of renting a rig can amount to $1 million or $2 million per day, renting a vessel costs $150,000 to $300,000 a day, Bin Xie said. The duration of vessel rental is however more dependent on weather conditions, she noted.

“No drill pipe will be used, as we used coiled tubing - spooled on a reel, able to be deployed and recovered from the vessel moon pool - to save operational time. This saving - from rig to rig-less and from drill pipe to coil tubing - usually cut the daily operational cost to 50% of comparable rig-operated interventions.”

According to Adegboyega Ehinmowo, Flow Assurance Researcher at Cranfield University, operators must take into account the availability of MSVs and ROVs, as they are often not available locally.

The choice of remediation technology should be made on a case by case basis, he said.

“There is always a trade-off between OPEX and CAPEX,” Adegboyega said.

According to Bin Xie, the production increase compared to the original blocked state varies per project, and FRS usually achieves more than 30% effectiveness.

Major operators such as BP, Shell, Chevron and Eni are using the Flowline Remediation System, she said.

Gulf of Mexico use

A traditional system used to eliminate the hydrate blockage involves a tubing that goes through the flowline and can physically break apart the blockage into several smaller blockages, Bin Xie said.

FRS uses an alternative depressurization method on both sides of the blockage, which eliminates the need of physical intervention, she said.

The system has been used on ten to fifteen large scale remediations in the last three years, as well as numerous remediations using a skid unit directly mounted on the belly of the ROV, Bin Xie said.

The technology can be used for most shallow water and deep water applications.

The deepest project FRS has been used on is the Shell-operated Perdido field in the Gulf of Mexico, which is more than 8,000 feet deep.

According to Bin Xie, FRS was used for hydrate remediation on Gulf of Mexico’s BP Thunder Horse T45 pipeline project, and the productivity of the flowline “increased dramatically.”

In the Gulf of Mexico, FRS has recently been used by operators Eni and Murphy, and is currently being used by Marubeni, she said.

“We are able to use a similar equipment spread - MSV, 2 ROVs, subsea intervention equipment, fluid transport conduit - hence saving time in mobe and demobe [mobilization and demobilization],” Bin Xie said.