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Forest Oil pipe has arrived; company’s permits being reviewed Company will convert Osprey exploration platform into development platform, build Kustatan production facility onshore, lay pipelines Kristen Nelson PNA Editor-in-Chief
The pipe for Forest Oil Corp.’s offshore pipeline to its Redoubt Shoal field has arrived and the company ‘s permits to turn its exploration prospect into a production project are under review.
The Alaska Division of Governmental Coordination public noticed Forest’s permit applications Jan. 15 and Bob Visser, a consultant working with Forest on design and installation of the pipeline, said Jan. 10 that coated pipe for the project was being offloaded from railroad cars in Anchorage.
DGS said public comments are due Feb. 19 on the proposal to develop the Redoubt Shoals prospect near the West Foreland area of Cook Inlet in township 14 west, ranges 7-8 north. Forest will convert its Osprey exploration platform into a development platform, construct the onshore Kustatan production facility and construct pipelines from the platform to the Kustatan production facility and then to existing pipelines.
Three pipelines Visser, speaking at a Cook Inlet pipeline forum in Soldotna, said the pipeline will come straight to shore from the Osprey platform to the onshore production facility Forest will build at Kustatan. From there, the new pipeline will connect to Forest’s West McArthur River unit facility on the West Foreland where it will go into an existing line which runs to the Trading Bay production facility. From there, Visser said, the oil will go into the Cook Inlet Pipe Line system to Drift River.
Three pipelines will be laid: for oil, for gas and a return line for produced water. The produced water, separated at the onshore Kustatan production facility, will be returned to the Osprey platform where it will be used for water flood.
Bored cased lines Shore problems will be avoided with the new pipelines, Visser said: “Instead of having a bluff cut we will actually create borings through the bluff that will terminate at minus 10 feet below low water.”
“We did a number of boring studies to make sure that we could actually do this,” he said: two desk studies and three soil borings at the site. A big concern had been that boulders might get in the way of the borings, but soil borings at the site didn’t encounter boulders, Visser said.
There will be four cased borings: three for pipelines and one for a power cable going to the platform. In something that is new for Cook Inlet, Visser said, power will be generated onshore and brought to the platform.
Pipelines pulled from shore The pipelines will be installed by making them up on shore and pulling them through the cased borings and up through the risers on the platform.
Studies were done to determine that the pipelines could be pulled all the way to the platform across the inlet bottom. Side-scan surveys were done in the inlet to make sure there weren’t boulders in the way.
Pipelines in the inlet have to have enough weight so that the bottom current can’t move them. On existing pipelines, part of that weight comes from a cement casing.
With this pipeline, Visser said, “we’re getting the stability by the additional steel rather than concrete.”
The three lines are extremely heavy: “heavier than the ones currently in the inlet. The wet oil line, the oil line to shire, has a wall thickness of three-quarter inch” as does the gas line, he said. The water line has a wall thickness of seven-eighths of an inch.
Pipeline coating done at plant The pipe was coated at a plant. Visser said the coating is a three-layer polypropylene system, 150 mils for the offshore line and 80 mils for the onshore line. “It’s extremely tough,” he said: “essentially impossible to scratch it.”
Polypropylene shrink sleeves will be applied where sections of the pipeline are welded together.
“We’ll also have an impressed current system, a cathodic protection system,” something common to Cook Inlet platforms and pipelines, Visser said.
A leak detection system will be installed on both the onshore and offshore pipeline segments, with “very accurate readings at both the input as well as the exit of the pipeline.” The pipeline system also has a built-in pressure sensor system.
The dual system looks at both the volume in and the volume out, and also at pressures, Visser said.
Vortex shedding common problem Vortex shedding, when the current in the inlet washes the support out from under pipelines, is a problem the industry in Cook Inlet has learned to compensate for, Visser said.
From 1965 to 1976 there were 14 pipeline failures due to vortex shedding, he said.
“At that time the industry program started and there has been no failure since then.” That industry program is an annual survey of pipelines which identifies spans where the bottom has been washed out. Sand bags or cement bags are then brought in to support any segment of a line longer than 50 feet and more than one foot off the bottom.
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