Intriguing findings from Great Bear’s wells
During a Dec. 13 talk to the Alaska Geological Society, Ed Duncan, president of Great Bear Petroleum, described some of the findings from two shale oil test wells that the company has completed this year. The two wells, drilled vertically, were planned for data gathering, to help determine whether, how and where to drill horizontal wells, to test the possibility of oil production direct from North Slope oil source rocks.
Two wells The Alcor 1 well, spud in June, reached a depth of 10,813 feet, while the Merak 1, drilled shortly after the Alcor well, attained a depth of 11,094 feet. Both wells were designed for maximum data recovery, with more than 600 feet of rock core being obtained in total, Duncan said.
The wells penetrated all three of the major North Slope source rock intervals: the Hue shale/HRZ, the lower Kingak and the Shublik.
Coring proved especially successful in the Merak well, where the drillers managed to core through to the Ivishak, the main reservoir rock for the Prudhoe Bay oil field. And, with the two wells being only about one-and-a-half miles apart, correlating the cores from the Shublik between the two wells should prove particularly illuminating, Duncan said.
Hue shale The Shublik is thought to have the most promise as a shale oil target. But the lower Hue shale and HRZ turned out to be very thick: about 900 feet in the Merak well and slightly less than that in the Alcor well, Duncan said.
“The zone is organic-rich and thermally mature and very clearly generating oil at this time,” he said. “From a research or regional study perspective we’re going to spend a lot of time over the next six months working this zone really hard, because it’s of high interest to us. It’s certainly going to provide a lot of hydrocarbon into anything in the lower portion of the Brookian and Kuparuk intervals.”
The “Brookian” refers to the youngest and shallowest major rock sequence within the petroleum systems of the North Slope, while the “Kuparuk” refers to sand units that reservoir oil in the Kuparuk River field. Some North Slope oil fields have oil reservoirs in the Brookian.
—Alan Bailey
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