Pressure caused by new drilling coupled with an improperly plugged well is suspected to have caused drilling mud to bubble out of an old well near Berthoud in late October.
“The cement and abandonment did not happen correctly,” Stuart Ellsworth, engineering manager for Colorado Oil and Gas Conservation Commission, said this week. “The records that we found were paper records that said the cement was there.”
But after digging up the well site to investigate the spill, officials learned that the required amount of cement plugs were, in fact, not installed. In a previous interview, Ellsworth explained that the general process of capping a well requires at least four layers of cement plugs at strategic locations.
“There was the top cement, and we believe that was all that was there,” Ellsworth said. “It was inadequate.”
Records, however, falsely indicated that the well, which was capped and abandoned in 1984, had the correct amount of cement plugs, according to the report. While it is unclear how this happened 34 years ago, the commission has changed its rules in the intervening years to prevent this type of occurrence.
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