Hilcorp plans Tyonek oil pipeline in parallel with new subsea gas line
Harvest Alaska, the pipeline subsidiary of Hilcorp Alaska, plans to lay a subsea oil pipeline under Cook Inlet from the Tyonek gas production platform to Ladd Landing on the west side of the inlet, with an eye to the possibility of future oil development from the platform. The company plans to lay the oil line in conjunction with the laying of a subsea gas pipeline, planned as part of Hilcorp’s Cross Inlet Pipeline project, a project to enable the shipment of oil west to east by pipeline under the inlet.
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“We do believe there is opportunity for future development of oil from the Tyonek platform,” Hilcorp spokeswoman Lori Nelson told Petroleum News in a March 2 email. “There are no near-term drilling plans, but the installation is being done in concert with the Cross Inlet Pipeline project to create efficiencies.”
Tyonek W 8 lineThe planned 8-inch oil pipeline, designated the Tyonek W 8 pipeline, is described in an application that Harvest has submitted to the National Marine Fisheries Service for an incidental harassment authorization for subsea pipeline laying in conjunction with the Cross Inlet Pipeline project. Harvest will need an approved IHA in case of minor disturbance to marine mammals in the inlet during the pipe laying operations. Cook Inlet beluga whales, which are listed as endangered under the Endangered Species Act, are found in the region of the planned work.
But the planned oil line is not part of the Cross Inlet Pipeline project - under that project Hilcorp will ship oil west to east under the inlet using one of the twin Cook Inlet Gas Gathering System pipelines that currently runs under the inlet. The new subsea gas pipeline from the Tyonek platform to Ladd Landing will carry gas under the inlet, to replace the gas carrying capacity that will be lost when one of the CIGGS lines is converted from the carriage of gas to the carriage of oil. An existing gas line runs between the Tyonek platform and Nikiski, on the west side of the inlet.
Capped for future useThe planned Tyonek W 8 oil line will remain unused, unless there is an oil development from the Tyonek platform - the IHA application says that, once laid, the pipeline would be capped for future use. There is a known oil pool under the North Cook Inlet gas field that the Tyonek platform serves. 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.
Laying of the Tyonek oil and gas pipelines will involve welding pipeline segments onshore at Ladd Landing and using a pull barge to pull the pipelines, in parallel, across the inlet to the Tyonek platform. The pipelines will be buried in the tidal transition zone and lie on the seafloor along the remainder of the pipeline route. Harvest plans to conduct the laying of the pipelines between April and mid-September of this year.
A known oil accumulationARCO discovered an oil pool, originally call the Sunfish accumulation, under the North Cook gas field when drilling the Sunfish and North Foreland exploration wells from jack-up rigs in the early 1990s. The prospect lies in a major geologic anticline called the Northern Lights anticline.
In 1998 Phillips Petroleum, which by then owned the leases for the North Cook Inlet field, conducted some appraisal drilling into the oil accumulation, which was then known as Tyonek Deep. The company applied for a right of way for an oil pipeline from the Tyonek platform to the west side of the inlet. But by early 1999 the company said that it had put a potential Tyonek Deep development on hold, waiting for oil prices to improve, to render the project viable. At that time the company said that it had tested two wells in the oil pool, had run completion tubing in a third well, and that the wells were ready for production.
The Phillips Alaska operations manager said that the company was evaluating the reservoir and that the development was not viable at that time. The development never happened.
In 2001 Conoco Inc. and Phillips Petroleum merged to form ConocoPhillips. ConocoPhillips continued as operator of the North Cook Inlet field.
Development consideredIn 2003 and 2004 Prodigy Alaska considered the possibility of an oil development at Tyonek Deep. The company said that, of 17 wells that had been drilled into Tyonek Deep by that time, 15 were deemed productive and eight tested at initial rates of up to 3,600 barrels of oil per day, per zone. Prodigy said that improved technology and higher oil prices since the 1990s could make the prospect viable. But, again, the development did not take place.
In 2014 Buccaneer Alaska Operating LLC proposed a Tyonek Deep development. At that time ConocoPhillips had farmed out the deep oil rights at North Cook Inlet. However, although Buccaneer initiated the permitting of a four-well drilling program, the development did not proceed.
In 2016 ConocoPhillips sold its 100 percent interest in the North Cook Inlet leases, including the Tyonek Deep section, to Hilcorp Alaska. It now appears that Hilcorp is eying the possibility of a Tyonek Deep development.
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