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More natural gas in Alaska Peninsula? With state’s Bristol Bay oil and gas lease sale on the horizon, Decker expresses doubts about Becharof well drill stem tests Alan Bailey Petroleum News Staff Writer
With the state of Alaska’s areawide lease sale for the Alaska Peninsula looming on Oct. 26 there’s quite a bit of speculation going around about just how much natural gas might lie under the peninsula and the adjacent state waters in Bristol Bay. During a presentation on Alaska Peninsula geology and geophysics at the Oct. 13 Geophysical Society of Alaska meeting Paul Decker of Alaska’s Division of Oil and Gas pointed out a couple of intriguing pieces of evidence for gas accumulations in the area. The Becharof well Decker said that the drill stem tests on the Becharof State No. 1 well, drilled by Amoco in 1984/1985, had shown gas flows of about 40 mcf per day. The Becharof well is located towards the northeast end of the lease sale area.
Apparently reports of numerous mechanical problems with the drill stem tests raise questions regarding the reliability of the test results — Decker thinks that there may well be much more gas in the area of the Becharof well than the test flow rates might suggest.
“If you look at that reservoir there it’s obviously much better,” Decker said. “There’s no reason why that well should have flowed at that kind of rate.”
Amoco was searching for oil at the time and may not have placed much emphasis on testing for gas. Decker also questions the knowledge of the subsurface structures at the time that the well was drilled.
“It’s an area without a lot of seismic data,” Decker said.
Petroleum News has found that the data for the Becharof well in the AOGCC files indicate that gas flowed at rates in the range 30 to 50 mcf per day from two intervals in the range 6,860 to 7,550 feet. The well summary refers to these intervals as “having excellent potential for generating large volumes of gas” and says that the interval from 7,180 to 8,860 feet is in the early phase of maturity for oil generation. Possible gas chimneys Decker also pointed out possible seismic evidence for gas chimneys, offshore the Black Hills area west of Port Moller. A gas chimney occurs when gas leaks from an imperfectly sealed reservoir.
Offshore seismic sections clearly depict tall, narrow vertical zones within which the stratification of thick Tertiary sediments appears to fade out. The seismic reflections deflect upwards at the zone margins. Decker compared the appearance and size of these seismic patterns with seismic depictions of known gas chimneys in the North Sea.
“You probably, in my view, bring the gas up from depth offshore there (in Bristol Bay), out of the Mesozoic,” Decker said.
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