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Foothills gets thumbs up Anadarko estimates Brooks Range Foothills contain as much as 2.5 billion barrels of oil, 40 TCF gas; Umiat recoverable crude set at 100 million barrels Kay Cashman PNA Publisher
Anadarko Petroleum Corp.’s preliminary reserves assessment for the Brooks Range Foothills indicates the region holds between 500,000 to 2.5 billion barrels of oil and 20-40 trillion cubic feet of natural gas at average depths of between 5,000 and 10,000 feet.
“We see the area as a robust petroleum system and look forward to exploring it in the future,” Greg Hebertson, who does corporate and strategic planning for Anadarko, told the joint western regional conference of the American Association of Petroleum Geologists and Society of Petroleum Engineers in Anchorage May 21.
Hebertson, who spoke of the exploration challenges and opportunities in the Brooks Range Foothills, said his presentation was co-authored by himself and Anadarko employees John Van Fleet, Jennifer Burton and Don Buscarello. According to Hebertson, Van Fleet “has played a key role in the evolution of Anadarko activity on the North Slope.” Robust petroleum system Anadarko is a major leaseholder and explorer in the Foothills, which has long been considered a gas-prone region. The Houston-based independent controls 3.3 million acres, either leased or under option, in the Foothills. Anadarko’s partners in some of the acreage include BP Exploration (Alaska) Inc. and EnCana (formerly Alberta Energy).
Hebertson defined the Foothills as “an area south of the Umiat meridian, north of the disturbed belt of the Brooks Range, east of the National Petroleum Reserve-Alaska and west of ANWR.”
Anadarko has been actively exploring the Foothills since mid-1999, having conducted “two proprietary seismic seasons and three field seasons” as part of its assessment of the Foothills petroleum system, Hebertson said.
A total of 46 exploration wells have been drilled in the Foothills to date, Hebertson said. The most recent well was drilled in 1994 but most of the wells date back to the two heaviest exploration activities on the Foothills – post World War II by the U.S. Navy and “pre and post Prudhoe Bay on the heels of the Prudhoe Bay discovery,” he said.
“The technical success rate to date is about 17 percent for the basin,” Hebertson said.
Some of the results of Anadarko’s assessment of the region came from analyses of data from the wells in the Umiat oil field, which was discovered in 1946 but never produced.
“Reserves are questionable in that area, but we think there’s up to about 100,000 million barrels recoverable from Umiat,” Hebertson said. Three to seven times more gas than oil Anadarko estimates there is three to seven times more gas than oil in the Foothills.
In addition to presenting promising technical data on area source and reservoir rock, Hebertson talked about the trap component in the region, noting it had a “propensity for multiple structural traps as in the case of the Umiat field.
“Seismic line across Umiat show hydrocarbons are reservoired in both the hanging wall and the foot wall of the structures,” he said.
“The seal capacity of traps – data from Umiat wells and field work and based on our analysis … show the seals are there and certainly capable of holding large hydrocarbon columns. The risk associated with that is breaching either by erosion or fracturing.” Unique environmental, cultural sensitivities “Anadarko certainly sees a robust petroleum system in the Foothills. Moving forward we need to address the associated risk,” Hebertson said.
The Foothills region has “unique environmental and cultural sensitivities” that present real challenges to seismic, drilling and production operations, he said. (See sidebar to this article.)
“Special emphasis for operators in the area needs to be placed on oil spill prevention,” Hebertson said.
A unique example of one challenge that faces explorers in the Foothills “came clear to us in 2001. We were working closely with state agencies and we were asked to identify the over-wintering pools of the Dolly Varden,” he said.
Locating those pools resulted in Anadarko’s rerouting its seismic shoot near the pools.
Another challenge in the hilly Foothills region that is not typical to the flatter coastal plain where the Prudhoe Bay, Kuparuk and Alpine fields are located is the use of wide tracked vehicle to protect the tundra surface.
“Unfortunately in the Foothills where there is much more snow, the wide-tracked vehicles became mired in deep snow,” Hebertson said,
Anadarko worked with its seismic contractor, PGS Onshore, to specially retrofit two track vehicles in order to improve traction and still protect the tundra.
“But with these challenges, we also see a lot of opportunities,” he said.
“We don’t know yet if there are commercial volumes and flow rates available to us in the Foothills but we’re certainly (going to) … continue to work the Foothills, and work around the tundra issues,” Hebertson said.
Anadarko’s Alaska spokesman Mark Hanley told PNA May 23 that the company hopes to drill its first well in the Foothills in the January to April 2003 drilling season, “but depending on the seismic work, and other factors, they may wait until 2004.”
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