Pump station 6 on the Yukon River is due to be closed around July 1. Photo courtesy Alyeska Pipeline Service Co.Alyeska Pipeline Service Co. plans to close another two pump stations on the Trans-Alaska Pipeline System (TAPS) about July 1 but said throughput capacity will not be affected.
Scheduled to be closed are Pump Station 2, near Franklin Bluffs, and Pump Station 6 at the Yukon River crossing.
Last summer, Alyeska decommissioned Pump Station 8, just south of Fairbanks, and Pump Station 10, north of Glennallen (see map, OGJ, June 10, 1996, p. 30). All the stations could be returned to full service within 6 months, and faster if necessary.
TAPS was designed to move 2 million b/d, but throughput now is 1.4 million b/d, down 100,000 b/d from last summer. It is expected to drop to 1.2 million b/d this summer, partly due to field maintenance operations at Prudhoe Bay field.
Meanwhile, Alyeska said a $100 million tanker vapor control project at the Valdez marine terminal is more than 65% complete and due to be finished late this year and in operation in first quarter 1998.
Shutdown rationale
Alyeska has been able to move crude with fewer pump stations because it is injecting a drag reduction additive.
The company will take Pump Station 12, north of the Valdez terminal, off line after 2000 when Prudhoe Bay production declines to 900,000 b/d.
Alyeska will require 3-6 months to decommission stations 2 and 6. Turbines that power the pumps and instrumentation will be removed and stored elsewhere.
Other equipment will remain onsite, and operable and cathodic protection on piping will remain active. Security will be maintained at the pump stations.
The company said the Alyeska employees at the pump stations will be reassigned.
It said Pump Station 6 has three turbines with combined capacity of 42,000 hp but typically operates with two units, or about 28,000 hp. Station 2 has two units with combined capacity of 32,000 hp, but usually operates with only one 16,000 hp unit.
Valdez facilities
The Valdez tanker vapor control system recovers hydrocarbon and inert vapors from the loading tankers and moves them into the existing vapor recovery system at the tank farm.
The vapors are used to provide pressure balancing in storage tanks as crude is emptied to fill a ship, as a fuel for electricity generation, or simply flared.
The Environmental Protection Agency issued rules, under the 1990 Clean Air Act Amendments, requiring better recovery of hydrocarbon emissions during loading of tankers.
The Alyeska work includes new vapor arms to connect to the vapor systems of ships at berths 4 and 5 and stainless steel pipeline systems from the berths to the existing vapor compressor building. Four of the five compressors are being upgraded.
The company said all of the high pressure piping-more than 10,000 ft-in the vapor recovery system will be replaced with corrosion resistant material by next year.
New tugs
Separately, TAPS Marine Shippers group is replacing two existing tugs at Valdez with powerful tractor tugs.
The firms are ARCO Marine Inc., BP Oil Shipping Co., SeaRiver Maritime Inc., Tesoro Alaska Petroleum Co., and Chevron Shipping Co.
The $12 million tugs fulfill conditions the Alaska Department of Environmental Conservation set in its approval of the TAPS Marine Shippers' Prince William Sound tanker contingency plans.
The shippers also have chartered a high-horsepower tug, Gulf Service, for deployment at Cape Hinchinbrook.
Copyright 1997 Oil & Gas Journal. All Rights Reserved.