A total-containment liner was installed on the upper deck of a Louisiana offshore platform in West Cameron 593A, by Unocal Exploration Corp.
The liner will help protect the environment during workover operations.
Unocal's major environmental concern was the oilbased packer fluid used in the wells.
Even though the platform workover rig, Hercules' Rig 11, was equipped with containment equipment which met federal regulations, Unocal wanted a secondary containment device to further guarantee that an accidental spill would not occur, according to Clyde Landry, Unocol's district production manager for the west offshore district, Louisiana region.
"The liner process works well onshore in reserve pits and I saw an application for it offshore," said Landry.
The 70 x 90 ft flexible-membrane liner, ULC 990, was built and installed by Unit Liner Co. of Shawnee, Okla. The job was completed in 7 days during February 1991.
The liner was installed in three sections to include lining the drainage troughs to funnel the spillover and wash water to a skimmer tank.
The liner was sandwiched between 3 in. x 12-in. boards laid on the deck grating. It was attached with an 18-in. rise to the side rails of the platform on three sides and to a 6-in. wall on the fourth side. The seamless liner also surrounded the base of the crane.
In addition to the stout thickness of the liner material (60 mil) further protection was provided by installing a geotextile cushion under the center length of the liner (Fig. 1). After installation, the openings for nine wells were marked on the top deck. (Fig. 2).
The workover unit rig up on each well slot will include gluing the liner to the piping that will connect the blowout preventers, on the upper deck, with the wellhead located on the deck below.
In the event of damage, the liner can be repaired on site, according to Russell Fregia, president of Unit Liner Co. Liner material and sealer enable a patch to be bonded just as a patch would be applied to a tire inner tube. The process was demonstrated during installation.
Cleanup is only a matter of hosing down the deck and the rig elements to be protected. The oil/water sludge drains down for separation in the skimmer tank. Waste fluids are shipped to shore and disposed of at approved sites.
After completing the workovers, the liner will be removed for storage onshore. Plans are to reuse the liner for other workovers that involve oil-based fluids.
Copyright 1991 Oil & Gas Journal. All Rights Reserved.
