Federal regulators have released a draft environmental study of options for developing what would be the North Slope's westernmost commercially producing oil field, a site within the National Petroleum Reserve-Alaska where ConocoPhillips hopes to start pumping oil in late 2017.

The Bureau of Land Management's draft supplemental environmental impact statement analyzes five alternative outcomes for the company's plan to develop its Greater Mooses Tooth 1 project, also known as GMT1. The draft, issued by BLM on Wednesday, is scheduled for publication in the Federal Register Friday and available for public review through April 22.

BLM, overseer of NPR-A, had previously approved ConocoPhillips' plan to develop the field now known as Greater Mooses Tooth. A 2004 BLM record of decision concluded that permits should be issued to develop this site -- then called Colville Delta 6 -- and others in the area, all of them considered satellites to the larger Alpine oil field on state land bordering the 23-million-acre petroleum reserve.

But between then and now, ConocoPhillips learned new information about Greater Mooses Tooth and modified its plans. The new plan for the initial drill site was submitted to BLM in July.

Initially, ConocoPhillips and its predecessor companies, ARCO Alaska and Phillips Petroleum, believed that the oil in the area was all part of a single Colville River Delta deposit that would support several Alpine satellites, said Serena Sweet, BLM's Alaska supervisor of planning and environmental coordination. Further geologic analysis revealed otherwise, Sweet said. "They realized that the reservoir was actually a separate reservoir," she said.

That resulted in the creation of a separate Greater Mooses Tooth Unit in 2008, and reclassification of the project as something other than a satellite, she said. ConocoPhillips is still planning to send Greater Mooses Tooth oil to Alpine facilities for processing, she added.

On the ground, company's modifications will "reduce the overall impact" of GMT1 development, the BLM's new draft says. The main changes are relocation of the drill site out of a setback along Fish Creek, a reduction in length of the planned connecting road and pipeline -- and a corresponding reduction of fill requirements -- and a longer bridge to cross the river in the area, BLM said in its draft.

The draft's five potential outcomes for the GMT1 proposal include a no-action alternative. There is no preferred alternative selected.

ConocoPhillips is already preparing its CD5 site, located northeast of GMT1, for production that the company expects will start in late 2015. Output from CD5 would be 16,000 barrels per day, according to ConocoPhillips.

GMT1 would produce 30,000 barrels a day, according to ConocoPhillips.

BLM's release of a draft environmental impact statement is good news because it represents movement toward production of new oil, Sen. Mark Begich said in a statement.

"I've been fighting for progress on expanded oil and gas development in Alaska, including in the NPR-A, since my first day in the Senate," he said in the statement. "Like the CD-5 project currently under construction, this will be a good step toward new oil production from the reserve."

Environmentalists appear to be warier. The Wilderness Society will be reviewing the draft environmental impacts statement, said Nicole Whittington-Evans, Alaska regional director for the organization.

Her group wants to ensure that "industry infrastructure will not be located in areas that are ecologically sensitive or important for subsistence uses, and that pipeline, road and aircraft impacts will be minimized," Whittington-Evans said in a statement.

"ConocoPhillips' anticipated oil production in this region needs to protect the region's outstanding values," she said, noting that the proposed development would lie between protected areas at Teshekpuk Lake and the Colville River.

ConocoPhillips, meanwhile, announced Tuesday that it hopes to embark on an expansion of production from the West Sak formation of relatively thick oil that lies within the Kuparuk unit.

The company said it submitted applications for various permits to construct what it is calling its 1H NEWS project in northwestern West Sak. The $450 million project would involve a nine-acre extension to the existing 1H drill site to accommodate new wells and associated facilities. ConocoPhillips said it hopes to start construction next year and begin production in early 2017.

The applications were made to the Alaska Department of Natural Resources, the U.S. Army Corps of Engineers and the North Slope Borough, said Amy Burnett, a spokeswoman for ConocoPhillips.

West Sak's oil has a consistency similar to cooking oil, Burnett said. That is thicker than most of the oil being produced on the North Slope. But it is not as thick as the oil held in the Ugnu formation, which is molasses-like and very difficult to produce, Burnett said.

Contact Yereth Rosen at yereth(at)alaskadispatch.com.