Partial results from a federal oil and
gas reserve assessment that surveyed domestic unconventional gas
reserves will be presented in September at AAPG's Rocky Mountain
Section Meeting in Laramie, Wyo.
The U.S. Geologic Survey's new oil and gas assessment
was begun in 2000 and is expected to be completed by 2006.
Results on the Piceance Basin will be presented by
Chris Schenk, project chief of the USGS National Oil and Gas Assessment
Survey, and staff geologist Deborah Higley will present results
on the Denver Basin.
"With time, perceptions change about oil and gas
and new resources come online so we periodically reassess the reserves,"
With this new assessment, the agency decided to conduct
the survey slightly differently. "We prioritized the basins in the
United States," he said.
Although the country has about 70 geologic provinces,
it has usually surveyed the "all 45 that contain oil and gas in
the past," he said.
But with this new assessment, the agency decided
to evaluate only the 25 largest basins.
"The top 25 contain about 90 to 95 percent of the
resources anyway, so we just focused on those this time," he said.
"That's a major change for us."
Another change is that this survey focuses on unconventional
resources, including basin-centered gas, tight gas, shale gas, coalbed
methane and gas hydrate.
"We're focusing on the unconventional gas … that's
where exploration in the U.S. is headed," he said. "As conventional
resources decline, we're looking at the unconventional. There's
certainly potential for gas there."
In the 1995 study — the most recent survey — the
agency tried to look at unconventional resources but discovered
it required a major effort, he said. Since then, the USGS developed
a new methodology to assess these unconventional resources.
So far, assessments have been completed on about
five basins around the country.
"We're taking a couple years for each one," Schenk
commented. "Coming up this summer, we'll do the Greater Green River
Basin in Wyoming, the San Juan Basin in New Mexico and Colorado,
and the Powder River Basin in Wyoming and Montana."
For the Greater Green River Basin, about 10 people
are working on the assessment over a two-year period, he said.
This study also focuses on more geologic analysis
than has been done in the past.
"We're giving them more time to do any area, so a
lot more geological framework will be published," he said.
After the Arab oil embargo, the USGS was given the
task of assessing the country's oil and gas reserves periodically,
and major assessments took place in 1975, 1981, 1989 and 1995.
The agency evaluates the onshore and state waters
portion of oil and gas reserves.
"We only do onshore and statewide," he said. "It's
for oil and gas and for all energy resources."
Meanwhile, the Minerals Management System, part of
the U.S. Department of the Interior, has responsibility for assessing
oil and gas reserves offshore.
"There is a strict division of duties there," Schenk
The results of the assessments always are made available
to the public.
"It's our estimate of what's remaining to be discovered,"