State approves connection of Tyonek oil line

Alan Bailey

Petroleum News

Alaska’s Division of Oil and Gas has approved a change in the plan of operations for Hilcorp Alaska’s North Cook Inlet unit, allowing Hilcorp to tie a planned subsea oil pipeline into the Tyonek platform.

As part of a project to enable the shipment of crude oil west to east under the Cook Inlet, Hilcorp plans to lay a new subsea gas pipeline between the offshore Tyonek platform and Ladd landing on the west side of the inlet. The idea is to ship oil under the inlet using one of the twin gas lines that form the existing Cook Inlet Gas a Gathering System, or CIGGS. The new gas line from the Tyonek platform, in conjunction with an existing gas line between the platform and Nikiski, will replace the gas transportation capacity across the inlet that will be lost when one of the CIGGS lines switches to the carriage of oil.

The Tyonek platform is the production platform for the North Cook Inlet gas field. However, there is a known oil pool known as Tyonek Deep under the gas accumulation. With an eye to the possibility of the future development of this oil resource, Hilcorp wants to lay an oil line from the platform to Ladd Landing concurrently with laying the new gas line. Although the planned oil line will not be used unless Hilcorp makes an oil development decision, the laying of the oil line at the same time as the gas line will presumably save significant pipe laying cost relative to laying the oil line separately. The planned oil line is designated the Tyonek W 8 pipeline, in reference to the pipeline’s eight-inch diameter.

The state’s approval of the tie in of the oil pipeline to the Tyonek platform only applies to work conducted inside the North Cook Inlet unit. On March 30 Alaska’s Division of Mining, Land and Water issued an approval decision for an easement for the complete pipeline.

- ALAN BAILEY