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This month in history: Anadarko well finds pay, low permeability
20 years ago this month: Company reports on Altamura 1 in NPR-A, drilled in 2001-02; also notes successful Lookout appraisal
Petroleum News
Editor’s note: This story appeared in the March 23, 2003, issue of Petroleum News Alaska.
The Altamura No. 1 well in the National Petroleum Reserve-Alaska, Anadarko Petroleum Corp.’s first operated well on the North Slope, encountered pay with low permeability, the company said in a recent filing with the U.S. Securities and Exchange Commission. It is the first indication of what the Altamura prospect, drilled in the 2001-2002 winter drilling season, might contain.
“Pay means they hit hydrocarbon bearing rocks or a formation,” which is good news, a state official told Petroleum News Alaska March 19, 2003.
“Permeability is standardized measurement of how easy a fluid, such as oil, will flow through a given unit of rock, because if the flow channels are very narrow and full of clay and silt then fluid can’t flow as easily as if the channels are large and don’t have a lot of debris in them. For example, clean sand has high permeability, whereas clay does not,” he said.
Producers of many North Slope reservoirs encounter permeability problems, the state official said, including the prolific and nearby Alpine reservoir.
“Low permeability means the well would produce, in relative terms, at lower rates. Permeability affects the flow rate, but not how much oil and gas is in the reservoir,” he said.
There are two common ways to address permeability problems on the North Slope. “You can drill vertical wells and fracture them or drill long, horizontal wells like they’ve done at Alpine, exposing a lot of the reservoir to well bore. Some of the Alpine horizontal wells are 3,000 feet long. … Either way, you can substantially increase your flow rate,” he said.
The Prudhoe Bay reservoir, he said, is “a high permeability reservoir. You can drill vertical wells and they flow at thousands of barrels a day with no stimulation at all.”
Anadarko renews drilling permit for Altamura No. 2 Anadarko said it had temporarily abandoned Altamura No. 1. Preliminary data released on the well in June said it was suspended April 11, 2002, at a measured depth of 9,100 feet and a true vertical depth of 9,041 feet.
The federal Bureau of Land Management said Anadarko’s drilling permit for Altamura No. 2 had expired in early January but was renewed on Jan. 17, making it good for another year.
Anadarko has not said if it intends to drill the Altamura No. 2 next season.
When the Bureau of Land Management did an environmental assessment of proposed Altamura exploration drilling the agency said the purpose of the project was to delineate the potential southern extension of the oil and gas formation discovered on nearby leases.
Altamura is the farthest south of current NPR-A exploration wells, some four miles south of the Rendezvous discovery.
Good news on Lookout well Anadarko also said it had “successfully appraised the Lookout discovery,” referring to the Lookout No. 2 well, drilled in the 2001-2002 North Slope winter drilling season. Anadarko is a partner in Lookout with Phillips Alaska Inc. (now ConocoPhillips Alaska).
Lookout was one of several NPR-A discoveries announced in May 2001 by Phillips Alaska, the operator, and its partner Anadarko. The companies said five wells and a sidetrack drilled in the 1999-2000 and 2000-2001 winter drilling seasons - all targeting the Alpine interval - encountered oil or gas and condensate. The wells included: Spark No. 1 and Spark No. 1A, Moose’s Tooth C, Lookout No. 1 and Rendezvous A and Rendezvous No. 2.
Anadarko said in its SEC filing that the Lookout No. 2 “encountered the Alpine equivalent reservoir” and tested at 4,000 barrels a day of oil and 8 million cubic feet a day of gas after fracture stimulation.
“An Alpine equivalent reservoir means they found a reservoir the same age as the Alpine reservoir,” the state official said.
“The challenge on the North Slope is finding good reservoir rock because we know there was a lot of oil generated up there, but finding good reservoir rock where it has been trapped is the challenge. The Alpine reservoir has been very successful,” he said.
Anadarko also said the Spark, Moose’s Tooth and Rendezvous accumulations in the same vicinity in NPR-A “require further delineation drilling and testing.”
ASRC leases in the works Anadarko told the SEC that is had interests in 3.14 million acres gross (1.2 million acres net) of undeveloped lease acres, 25,000 gross (6,000 net) acres of developed lease acreage and 16,000 gross (8,000) net fee acres at year-end 2002.
The company said it is also finalizing agreements on 181,000 gross (60,000 net) acres in the Foothills area of the North Slope from Arctic Slope Regional Corp. This is under an exclusive option-to-lease agreement which has been in effect with ASRC since 1998; terms of that agreement are confidential.
Anadarko said it retains the right to acquire leases on an additional 1.94 million gross (647,000 net) ASRC acres based on the option-to-lease agreement.
In NPR-A, Anadarko said, it has lease interests totaling 910,000 gross (289,000 net) acres.
The company said that in total it has “access to approximately 5,380,000 gross (1,923,000 net) acres in Alaska through current and pending leases or options.”
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