BISMARCK, N.D. -- Testing showed that underground water supplies are safe after a ruptured oil well leaked more than 2,500 barrels of crude oil and water in western North Dakota, and it appeared the leak had been cleaned up, the state Health Department said Tuesday.
Health officials tested three water wells near farms and two that supply the city of Killdeer, after a well near that city broke last week, said Dave Glatt, director of the state Health Department's environmental health section.
"We didn't find anything other than what's naturally there," Glatt said Tuesday.
Denbury Onshore of Plano, Texas, said its well 2½ miles southwest of Killdeer began leaking early Wednesday and was temporarily corked Friday with heavy mud and concrete plugs.
Bob Cornelius, the company's vice president of operations, said Tuesday that the leak has been cleaned up. The 2,255 barrels of water used in drilling operations and 251 barrels of oil have been recovered, the company said.
"We got things buttoned up and we're doing diagnostic testing," Cornelius said. "Everything is safe."
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Dennis Fewless, director of water quality for the state Health Department, said one farmer's water well is within a half mile of the broken oil well. Killdeer's drinking water wells are more than a mile away, he said.
Three monitoring wells have been drilled near the crippled oil well to test groundwater in the area. Glatt and Fewless said tests would be ongoing for at least two months.
The ruptured oil well, dubbed Franchuk 44-20 by the company, used horizontal drilling and hydraulic fracturing, a process that uses pressurized fluid and sand to break open oil-bearing rock some two miles underground.
Cornelius said the steel and concrete casing within the wellbore failed during hydraulic fracturing operations. "It appears the 7-inch casing failed right below the wellhead," Cornelius said.
Wells in North Dakota's oil patch cost more than $4 million to drill, industry officials say.
Cornelius said the company hadn't decided whether it will repair the wellbore or permanently plug it.