|
Work continues on abandoned oil line from Anna platform Pipeline determined to have been cause of July “mystery sheen” in Cook Inlet; 50-75 barrels of crude have been recovered in vacuum operation; permanent fix planned for spring Petroleum News Alaska
The Alaska Department of Environmental Conservation said Sept. 27 that work continues on an abandoned crude oil line from the Anna platform, determined to have been the source of a July Cook Inlet sheen.
The sheen was reported by a commercial aircraft pilot 10:40 a.m. July 31 near Middle Ground Shoal approximately 1.5 miles north of the Baker platform. DEC said Unocal conducted an over flight of the area at 11 a.m. July 31 and found the slick to be 30 feet wide by 1.5 miles long with 30 percent coverage. Sheen was also observed during over flights intermittently at slack tide until Aug. 11. No sheen has been observed since.
The cause was determined to be leakage from an abandoned Anna platform subsea crude oil pipeline. DEC said that laboratory analytical results received Aug. 29 indicate the mystery sheen samples were from crude oil in the Anna pipeline, with differences among the samples attributed mainly to weathering. Focus on abandoned pipeline Unocal is maintaining a 24-hour vacuum on the pipeline, periodically withdrawing fluids. DEC said recent fluid samples appear clean. Approximately 280 barrels of fluids have been extracted to date, containing 50-75 barrels of crude oil.
The fluids have been taken to the Cross Timber facility for treatment and disposal.
DEC, U.S. Coast Guard and Cook Inlet Regional Citizens Advisory Council personnel met with BP and Unocal Sept. 21 to discuss correction action options. Amoco, since acquired by BP, was the original operator of the Anna platform.
DEC said that until additional data becomes available on the condition of the abandoned crude oil pipeline, agency representatives agreed to maintain a continuous vacuum on the pipeline until a permanent solution is found. Pipeline installed in 1966 DEC said two pipelines — one oil and one gas — were installed from the Anna platform to East Forelands approximately 19 miles away in 1996. DEC said that from 1996 to 1974, “frequent failures occurred from the crude oil pipeline, which was shut down.”
A portion of the oil pipeline was purged in 1974 by pigging, severed from the remainder of the line, and crossed over to connect with the gas line. This line was used to transport gas from the platform to East Forelands.
In 1983, several leaks were found in the gas line between Middle Ground Shoal and the East Forelands and it was shut down. Amoco abandoned the gas line in 1986.
The portion of the crude line that was not connected to the gas line was blind flanged and abandoned in place. It is this line that has been determined to be the source of the sheen. The distance from East Foreland to the severed end of the crude oil pipeline is 84,000 feet (15.9 miles). Vacuum will be continued Unocal will continue to maintain a vacuum on the abandoned crude oil pipeline and remove oily fluids as they are available, and will continue to submit a weekly operational report to agencies. Unocal will also continue over flights of the area where the sheen was originally observed during routine platform flights.
DEC said BP and Unocal are coordinating development of a long-term plan to address the removal of residual crude oil in the abandon pipeline, and intend to implement that plan in the spring. Upon receipt of the plan, DEC will distribute it to resource agencies for review, comments and approval. DEC said that a plan to provide for freeze protection of the shore-side pipeline must also be prepared.
| 