Chesapeake Energy Corp. said Friday it will immediately resume completion operations in Pennsylvania, a little more than three weeks after voluntarily suspending them following a well blowout in the northeast part of the state.

"We have engaged in a rigorous investigation of the cause of the incident, a thorough examination of our existing operations, and a comprehensive environmental evaluation of the area surrounding the location," said John K. Reinhart, Chesapeake vice president of operations for its eastern division. "We have learned from this and have taken steps to mitigate the risk of this type of event happening in the future. We are very confident that we will safely resume our completion operations."

The incident occurred at around 11:45 p.m. EDT on April 19 at the Atgas 2H well in Bradford County (see Shale Daily, April 25). According to Chesapeake, a valve flange connection to the wellhead failed during completion operations, which caused fluid to discharge at high pressure.

"An equipment failure of this type is extremely rare in the industry and is the first valve flange failure of this magnitude in more than 15,000 wells Chesapeake has completed since its founding in 1989," Chesapeake spokesman Brian Grove said.

Grove said Chesapeake personnel responded immediately to the accident and notified the Pennsylvania Department of Environmental Protection (DEP). Although the well was brought under control by 3:50 p.m. EDT on April 21, the company estimated that 240 bbl of well fluid and rainwater had flowed over the top of containment berms at the well site and onto adjacent land. Chesapeake added that a "limited amount" -- about one barrel -- of highly diluted chemicals used for hydraulic fracturing entered an unnamed tributary of Towanda Creek.

According to Grove, the company used vacuum trucks and constructed a diversion channel to help contain the spill, and the recovered fluids were placed into steel tanks, treated and disposed. "Chesapeake began extensive surface and well-water sampling the day of the incident and continues daily testing today," Grove said. "The [DEP] has also taken extensive samples from both surface water and nearby water wells. To date, our testing results indicate minimal and localized impact to the environment immediately surrounding [the Atgas 2H well], and no impact to Towanda Creek or the Susquehanna River."

Grove said a small farm pond near the well was drained in coordination with the DEP, and the pond water was taken to a Chesapeake wastewater recycling facility. He added that the water quality of private water wells, the unnamed tributary and Towanda Creek were all continuing to be tested.

So far these tests show "results at or near the same water quality indicated by samples taken prior to drilling activity," Grove said. "Thus far, ecological assessments of both streams have shown no indication of any fish kills or other adverse impacts." He added that some soil would likely need to be excavated to restore the affected area.

Grove said every wellhead in the company's eastern division was disassembled, pressure tested and reassembled. He added that the company has changed its oversight and documentation procedures and has started a new, independent auditing system for wellhead assemblies.

"We are confident that this was an isolated incident and that all wellhead equipment and connections are fully functional and structurally sound," Grove said.

The DEP issued a notice of violation to Chesapeake after concluding its investigation into the incident (see Shale Daily, April 26).