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Vol. 22, No. 38 Week of September 17, 2017
Providing coverage of Alaska and northern Canada's oil and gas industry

Pipeline plan filed

More details on Hilcorp’s Liberty development included in right-of-way application

Alan Bailey

Petroleum News

A right-of-way application package filed with the Alaska Department of Natural Resources for the construction of a pipeline system running onshore from Hilcorp Alaska’s planned Liberty oil field in the Beaufort Sea includes detailed plans for both pipeline construction and for the development of the oil field itself. Hilcorp Alaska’s pipeline subsidiary, Harvest Alaska LLC, has filed the application in recognition of the fact that, although the oil field facilities would be located on the federal outer continental shelf, the pipeline system will traverse state land offshore within three miles of the coast, as well as onshore.

As previously reported in Petroleum News, Hilcorp plans to develop the field from an artificial gravel island, about five miles offshore in Foggy Bay, about 15 miles east of Prudhoe Bay. The island would have a surface area of 9.3 acres and a seabed footprint of about 24 acres, in 19 feet of water, with the surface of the island 15 feet above low tide level. The sloping sides of the island would be protected by an armor of linked concrete mats, a protection system successfully used in other Beaufort Sea artificial islands, Hilcorp’s plan says.

Hilcorp anticipates production starting at 10,000 to 15,000 barrels per day of oil and peaking at 60,000 to 70,000 barrels per days within two years of field startup, with total recovery between 80 million and 150 million barrels over 15 to 20 years. The total recovery estimate represents a 55 percent recovery factor from an estimated 230 million barrels of oil in place, Hilcorp’s plan says.

Permits needed

Currently, Hilcorp is waiting for the completion of a Bureau of Ocean Energy Management environmental impact statement before the project can proceed. Once the company has the EIS and the permits that it needs for the project it will review permit stipulations and work with the other field owners to determine whether the development remains viable: That review process will likely take at least six to nine months, the Hilcorp plan says. Following financial approval by the owners, development would start with detailed engineering for the project. The construction of the Liberty island would happen in year two of the project. Pipeline construction would take place in winter, during the first half of year three.

First oil is expected in the first quarter of year four of the development.

Hilcorp says that it is designing the offshore production facilities to use modules small enough to be trucked to the North Slope on the Dalton Highway. The modules and equipment for the facilities may be barged to the island from the North Slope during the summer, or trucked over an ice road in the winter. Facility installation and on-site construction will begin in year two of the development and will be completed by the end of year four. The use of small modules rather than larger units barged from out of region offers several benefits, including the use of proven module designs; shorter engineering and fabrication times; and flexibility, if needed, in adjusting to a higher than anticipated production rate, Hilcorp’s plan says.

The pipeline system

The pipeline system that will connect the Liberty island to the mainland will actually include two pipelines: an oil line for the export of pipeline grade crude oil from the field production facilities, and a utility line for the delivery of fuel gas to the island and for other potential uses. The pipeline bundle will include a fiber optic cable for communications with the offshore facilities. Design life of the system is 25 years, although appropriate maintenance may enable the system to continue operating longer, the plan says.

The 5.6-mile offshore section of the pipeline bundle will be buried nine to 11 feet beneath the seafloor, with a minimum depth of seven feet of fill cover above the bundle. Landfall will be at the coast, to the west of the Kadleroshilik River. The 1.5-mile onshore section will be above ground, with the two pipelines held on vertical support members. The oil line will connect with the existing Badami pipeline, for the shipment of oil to the trans-Alaska pipeline. The concept for the offshore section of the oil line is a pipe-in-pipe design involving a 12-inch oil pipeline inside a 16-inch diameter casing. The utility line will be four inches in diameter.

The pipeline system will incorporate leak detection technologies, including the vacuum testing of the space between the offshore oil pipeline and the outer pipeline casing, Hilcorp’s plan says.

Winter placement of the gravel for the offshore island and winter laying of the pipeline system will avoid noise disturbance to bowhead whales that traverse the region in the summer and form an important subsistence resource for local communities, the plan says.

Drilling rig

The drilling rig and associated equipment will be mobilized to the island by barge in year two of the development, with start-up of the drilling scheduled for the first quarter of year three. Hilcorp says that it may use an existing drilling rig, its Rig 248 that currently operates in Cook Inlet. Alternatively, the company may build a new rig that would be portable and adaptable, and thus usable both at Liberty and for other North Slope projects. Whichever rig is used, the rig would have new, low emission engines and use new or reconditioned drilling equipment, Hilcorp’s plan says.

Used drilling mud will be disposed in a disposal well, the plan says.

The design of the Liberty island will accommodate five to eight production wells, four to six injection wells and up to two disposal wells. Directional drilling will enable access to various parts of the subsurface reservoir. All wells will be completed by the end of the second quarter of year five of the development. Seawater, at some stage supplemented with produced water, will be injected for reservoir pressure maintenance. And any produced gas would be used as fuel, or for artificial lift from production wells, or for injection into the reservoir.

Kekiktuk reservoir

The oil reservoir for the Liberty field is in sandstones of the Kekiktuk formation of Mississippian age, the same rock unit as forms the reservoir for the Endicott field, a few miles to the northwest. At Liberty the oil column is about 380 feet thick, from the top of the mapped reservoir structure to a tar-mat at the base of the oil. Water lies under the tar mat. The oil has a gravity of 24 to 27 API. And there is the possibility of a gas cap above the oil, although gas has not been encountered by wells drilled into the reservoir, Hilcorp’s plan says.

Reservoir rock properties are similar to those at Endicott. Zone two of the reservoir has the best reservoir quality, with a net-to-gross ratio of more than 90 percent, Hilcorp’s plan says. Subzone 2A has an average porosity of 18 to 19 percent and is 80 to 150 feet thick. Subzone 2B is 80 to 140 feet thick and has a porosity of 18.5 to 21 percent. The rock has excellent permeability.



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