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Foothills gas fields not expected to be large Multiple fields, close together, needed for economic development, oil chief says Kristen Nelson Petroleum News Editor-in-Chief
Don't expect to find large gas fields in the foothills of the Brooks Range. Look instead for smaller gas fields, closer together, Mark Myers, director of the Alaska Division of Oil and Gas, told the Alaska Natural Gas Development Authority July 28.
Myers was reviewing Alaska's natural gas resources for the authority board, and he said that in addition to the known 35 trillion cubic feet at Prudhoe and Point Thomson, a lot of the remaining 65 tcf that's part of the 100 tcf of technically recoverable gas you hear about on the North Slope would come from the foothills.
"We haven't proven up the reserves there, but we do know all the wells had pretty good gas shows," he said.
The Lisburne limestone, produced at the Prudhoe Bay field, occurs in the foothills. The Lisburne is "very, very thick, and it's in folded structures, very large geologic structures, thousands of feet thick."
The question, Myers said, is "how laterally extensive" are the zones which "have better quality reservoir that could preserve significant volumes of gas?" And, how well fractured and interconnected are those zones? Over-thrust area Geologically the area is "very prospective," he said: "it looks very much like the over-thrust belt in western Canada, or somewhat like the Rocky Mountain stuff."
Myers said companies like Petro-Canada and EnCana, "the leading producers of that play trend in the Canadian Rockies," see the surface geology in the foothills, and the little bit of seismic they have, as "very, very similar to that play (in Canada). They're real comfortable with the play concept."
And, Myers said, those companies, along with Anadarko Petroleum, have acquired large acreage positions in the Alaska foothills lease sales.
So far, however, the companies have not proved up on the reserves.
"You clearly need a couple of things: you need the wells drilled; and we need long-term tests on those resources," he said.
And you'll need a string of small fields, close together, to make production economic.
Because the foothills is an over-thrust belt, Myers said, "it's unlikely that in an over-thrust belt you're going to find a single 10 tcf field; they're going to be smaller, but they're going to be fairly close together."
A field size of half a trillion cubic feet would probably be the minimum for economic production, he said, and you'd need a string of those fields to make production economic.
Development in the foothills, he said, will require drilling "multiple wells on multiple prospects," and proving them up, "to know you have enough gas to actually produce an economic project."
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