Chevron — and Unocal, which it acquired in 2005 — have held leases on Alaska’s North Slope since before production began there in the late 1970s. While some of that acreage is part of producing fields operated by other companies, Chevron and Unocal haven’t been active in North Slope exploration in recent years. Although Chevron and Unocal currently hold extensive exploration acreage in northern Alaska, the companies haven’t drilled north of the Brooks Range in more than a decade.
Unocal’s last North Slope exploration effort was the Amethyst State 1 well in 1994; Chevron drilled the Karluk 1 onshore in 1989 and the Diamond well in the Chukchi Sea on the outer continental shelf in 1991.
That will change this winter season, with Chevron planning to drill up to six wells in its first exploration drilling season at the White Hills prospect, with the potential for additional wells in subsequent years.
Unocal (Union Oil Company of California) “a wholly owned indirect subsidiary of Chevron Corp.,” told the Alaska Department of Environmental Conservation in a recent application that it “plans to conduct a regional, multi-year onshore oil and gas exploration drilling program during the winter months on the North Slope” at its White Hills prospect in the Brooks Range Foothills, west of the Sagavanirktok River and east of the Colville River.
The company said mobilization would begin with a staging area and camp at the Franklin Bluffs pad, Milepost 39.6 along the Dalton Highway, during the fall and early winter.
Acreage acquisition began in 2001The initial White Hills tracts were acquired by Unocal in 2001; the company added 48 tracts in the March 2006 state areawide lease sale. The White Hills acreage includes Unocal’s 1994 Amethyst well as well as BP’s 1991 Malguk 1 well.
Former Alaska Division of Oil and Gas Director Mark Myers (currently director of the U.S. Geological Survey) told Petroleum News in 2006 that White Hills is close to the 1966 Susie well that Richfield drilled just before Prudhoe Bay was discovered (see “Chevron to begin North Slope exploration in 2007” in June 11, 2006, issue of Petroleum News). That well had oil shows and he said while the well was unsuccessful “there is still significant interest in that area for oil.”
“The oil-stained outcrops … around Sagwon Bluffs illustrate the area contains oil,” he said.
Myers said targets in the While Hills prospect would include Cretaceous sands, including the Kuparuk River formation.
DO&G petroleum geologist Paul Decker told Petroleum News last year that both the Amethyst and Malguk wells penetrated thick Upper Cretaceous deepwater turbidite sands with good oil and gas shows. Decker said Phillips Petroleum’s 2002 Heavenly 1 well (section 4, township 4 north, range 8 east, Umiat Meridian), just west of White Hills, had the same Cretaceous interval and that the same sands may extend within the Chevron acreage.
2-D seismic acquired last winterLast winter the company conducted 2-D seismic on the North Slope and Nabors Alaska Drilling is building a lightweight, high-tech AC drilling rig which Chevron plans to use at While Hills this winter.
Nabors Rig 106 for Chevron, along with Rig 105 for Anadarko Petroleum, will be the first “purpose-built AC rigs for the North Slope,” Dave Hebert, Nabors’ general manager for Alaska, told Petroleum News earlier this year (see March 11, 2007, Oil Patch Insider).
Hebert said Rig 106 will be used first at Chevron’s Happy Valley field on the Kenai Peninsula and then taken to the North Slope before the end of the year.
John Zager, Chevron’s Alaska general manager, said in November that Chevron planned to have a rig on its White Hills prospect, some half million exploration acres, in 12 to 14 months. The rig, he said, will be a “smaller, more portable, built-for-purpose rig.”
Ice road from Franklin Bluffs
The company said potential first-season wells include: Smilodon, Mastodon, Panthera, Stegodon, Gulo, Megatherium and Titanothere.
Access to the wells will be by a 35- to 50-mile snow-ice road from the Franklin Bluffs staging area. Smilodon is 34 miles west of the staging area. An ice road would run north from Smilodon to Panthera and then fork west to Stegodon and east to Gulo.
From Smilodon another ice road would run south to Mastodon, Megatherium and Titanothere.
Well locations for those wells that might be drilled this winter are included in Chevron’s application for approval of an oil discharge prevention and contingency plan: Smilodon (9-T4N-R9E, UM), Mastodon (6-T3N-R9E, UM), Panthera (27-T6N-R9E, UM), Stegodon (34-T6N-R8E, UM), Gulo (8-T6N-R10E, UM), Megatherium (27-T3N-R9E, UM) and Titanothere (8-T2N-R9E, UM).
In addition to those with locations, the application lists six other wells by name only — Glyptodont, Dinictis, Mammoth, Indrico, Woolly and Creodont — for a total of 13 proposed wells.
Smilodon is closest to Malguk (28-T4N-R9E, UM). Amethyst State 1 (12-T2N-R7E, UM), is farther south in the White Hills prospect than any of the wells proposed for drilling in the 2007-08 winter season.
The exploration drilling operations will be on ice pads with snow-ice road access from the existing road structure, the company said. A trail would be established using Rolligons as tracked vehicles to pre-pack the route to promote frost penetration. Then a spike camp with work crew would be mobilized to begin construction of primary snow-ice road access route and the first drill site ice pad. The drilling rig, camp and ancillary equipment would be mobilized once snow-ice road access and the first ice pad are established. Chevron said additional snow-ice road routes and drill site pads may be constructed depending on operational needs for the season.
Well names distinctiveThe well names at While Hills are a mouthful — Chevron said the wells were named for extinct mammals:
Smilodon: extinct saber-toothed tiger;
Mastodon: extinct elephant;
Panthera: extinct panther; and
Stegodon: another extinct elephant.
A Google search provided descriptions for others of the well names:
Gulo: wolverine (presumably reference to an extinct variety);
Megatherium: extinct giant sloth;
Titanothere: extinct large herbivore distantly related to rhinos and horses;
Glyptodont: extinct armadillo;
Dinictis: extinct cat; false-saber-toothed tiger;
Mammoth: extinct elephant;
Woolly Mammoth: extinct mammoth; also called tundra mammoth; and
Creodont: extinct carnivore.