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Wyoming report: Pavillion gas wells properly drilled; more study needed
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Wyoming report: Pavillion gas wells properly drilled; more study needed

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Natural gas wells in the Pavillion Gas Field were properly drilled and maintained, but more study is needed to prove if energy operations contaminated drinking water in the region, according to a draft report released by Wyoming regulators Wednesday.

Those findings were among the conclusions of a preliminary study released by the Wyoming Oil and Gas Conservation Commission. The report is one of three investigations Wyoming is conducting into polluted drinking water near the town of Pavillion. The state is also reviewing disposal pits and testing water quality in the area. All three investigations will be combined in a final report. 

Wyoming Oil and Gas Supervisor Mark Watson said Wednesday's draft contained "no major conclusions as far as potential for contamination."

"That won’t be done until the final report," he said. 

The source of the pollution has long been the subject of fierce debate. Environmentalists argue the industry practice of hydraulic fracturing, or fracking, is the cause. Industry representatives contend the contamination occurs naturally in the rocks where water wells were drilled. 

The U.S. Environmental Protection Agency initially and tentatively reported natural gas operations in the region were the cause of nearby polluted well water but later backed away from that claim.

Reactions to the report's findings ranged widely. 

John Fenton, chair of the Pavillion Area Concerned Citizens, said he was frustrated by what was not in the report. A well across from his house was among three wells identified as lacking cement bond logs. A well in his field was one of seven listed as in need of a mechanical integrity test. 

"What is looks like to me is we are set up for years of testing and monitoring," Fenton said. "Answers are a damn long way off."

Encana, for its part, praised the investigation. The findings show wells in the field were properly constructed and provide no pathways to pollute drinking water, said Doug Hock, a company spokesman. 

He said the finding of deep  water wells was not surprising. Those water wells were drilled through gas bearing rock, Hock said. The report found rock containing gas began at 699 feet in places while wells were drilled to 750 feet.

"Our contention is the water wells were drilled further than they should been," Hock said. 

An EPA spokesman said the agency was aware of the report and was reviewing its findings.

The draft unveiled Wednesday is the first study to examine the integrity of wells in the gas field. The state's investigation was based on company filings to the oil and gas commission, the Office of the State Engineer and other government data. 

The study appeared to raise as many questions as it answered. 

It concluded "all wells were properly permitted, drilled, completed, and operated in compliance with applicable state and/or federal rules and regulations." 

Mechanical integrity tests of five wells showed no signs of leaking wells. 

But the report also found the casing on 30 percent of the 50 natural gas wells reviewed was shallower than three nearby water wells.  One water well was deeper than the casing of 10 nearby gas wells. 

Natural gas wells are encased in cement to prevent leakage. 

That means contamination from a natural gas well could leak into the water well below it. The possibility also exists that naturally occurring gas found in those water wells could have contaminated other sources of drinking water. 

Either way, more information is needed, the report said. 

"The presence or absence of cement is only one of several factors to be considered in determining if a potential pathway exists behind the casing that could allow migration upward or downward," wrote Robert King, the report's author. "Other factors include hydrostatic pressure differentials, formation rock properties (permeability and porosity), gas/water contacts, location with respect to other wells, geologic and hydrologic environment, and drilling mud characteristics."

Complicating matters further is a lack of information on the water wells drilled in the area. Seven of the 15 water wells reviewed for the report do not have a permit filed with the Office of the State Engineer, which regulates water use. Information on when those wells were drilled, their depth and casing size, among other details, were missing, the report said. 

Wyoming is also missing information on how individual gas wells were fracked. The Pavillion field has been in production since the 1950s, but some wells have been fracked in the time since. Fracking is a process in which water, sand and chemicals are injected into a well at high pressure to stimulate oil or gas production. 

Wyoming began collecting information on chemicals used in fracking in 2010. 

King recommended the state obtain the missing information on water wells and stimulation. Geologic and hydrologic studies are also needed to better understand the flow of gas and water between rock formations in the area, he said.  

The task of determining which wells were fracked could be especially difficult, Watson said, as ownership of the field has changed hands several times. Records of what was done by a previous owner might have been lost, he said.

The findings released Wednesday will be sent to Encana Oil and Gas, the operator of the field, and EPA for comment and review. The public will be given 30 days to comment on the initial conclusions as well. 

Initially, the draft was to be kept private, but the state reversed course after landowners appealed to share the preliminary findings with the public. A spokesman for Gov. Matt Mead praised its release, saying the state needs "valid and reliable information" regarding Pavillion's water while stressing it was only a draft.  

This article was updated to correct two errors. An earlier version said some natural gas wells were shallower than three water wells. They are not. The cement casing on those natural gas wells was shallower than the water wells. The state also has information on which wells were fracked, but does not have information on the chemicals used in frack jobs.  

Reach energy reporter Benjamin Storrow at 307-335-5344 or benjamin.storrow@trib.com. Follow him on Twitter @bstorrow

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