Improving efficiency and reducing cost through pipeline flushing

The MER U.K. Forum was set up to maximize economic recovery from the U.K. Continental Shelf and maximize overall value for the U.K. from the oil and gas industry. Conoco­Phillips U.K. teams have effectively optimized pipeline flushing and cleaning procedures on 19 gas/methanol pipelines, using a methodology — considered one of the key successes of MER U.K. — developed by challenging industry approaches.

Hood photo
Andrew Hood

“Over the past two years in the Southern North Sea, Conoco­Phillips has worked with a vendor to develop a series of cleaning chemicals and gels,” said Andrew Hood, engineering supervisor, Well Operations/Well Abandonment. “Injecting these into the pipelines has given a transformational solution to flushing and cleaning work scopes. The chemicals have been successfully used to displace process fluids in the pipelines using seawater while minimizing the amount of over-flush of seawater and volume of contaminated liquid to be disposed of to reach the desired level of cleanliness.” The process uses cleaning products with the lowest potential environmental hazard and minimizes discharges to the marine environment by using downhole reinjection or containment for onshore treatment and disposal as appropriate.

“Designing the pipeline cleaning process in close collaboration with a specialist vendor has enabled U.K. Decommissioning to develop a highly effective program, with full consideration for the environmental sensitivities in the marine-protected areas of operations,” said Paul Hatton, senior environmental scientist.

Hatton photo
Paul Hatton

Conoco­Phillips is now collaborating with several operators with producing facilities (satellite platforms and subsea manifolds) tied into the Lincolnshire Offshore Gas Gathering System (LOGGS) complex and the Murdoch central hubs, to share this knowledge. The first combined operations project was completed successfully with operator Centrica, employing a dive support vessel DSV) to tie into its subsea Ann manifold and pipeline before pigging and flushing the process fluids toward the LOGGS platform for injection down-hole.

Combined teams operated on the DSV and the LOGGS platforms on a 24-hour basis, leveraging their expertise and ensuring the task was completed safely and successfully within schedule. Approximately 4,500 barrels of fluids were received and disposed of at LOGGS. This successful result will have a significant impact on the management of future third-party pipeline cleaning operations.