By Ellen M. Gilmer, E&E reporter
(Originally published 8/7/2014 by Environment & Energy Daily. Contact E&E for republication permissions.)
The latest round in a yearslong investigation of water contamination in a Wyoming natural gas field has left most questions unanswered.
A draft report released yesterday by the Wyoming Oil and Gas Conservation Commission found that gas wells drilled near the town of Pavillion were properly permitted and constructed but that researchers needed more water well information and pressure monitoring to do a full analysis.
The conclusions were celebrated by Encana Oil & Gas Inc., the driller accused of causing the contamination.
“The report confirms that the natural gas wells in the Pavillion Field were soundly constructed and provide no migration pathway into domestic water wells,” a company spokesman said yesterday.
The review, prepared by engineering consultant and former WOGCC interim chief Bob King, is one of three concurrent state investigations into Pavillion water contamination that residents began reporting in 2009. U.S. EPA conducted a high-profile probe that linked Encana’s hydraulic fracturing to the tainted water wells, but the agency abandoned the preliminary research last year — leaving the investigation in the hands of state officials with the help of a $1.5 million grant from Encana (EnergyWire, June 21, 2013).
This week’s draft report draws no final conclusions but reviews 15 water wells in close proximity to natural gas wells in the area. Of those, three were deeper than the casing of nearby oil and gas wells. For example, one water well is listed at 750 feet deep. Less than a quarter-mile away, a gas well’s casing extends down only 518 feet. That means the gas well is not sealed off at the depth where the water well draws groundwater.
Nine more gas wells within a quarter-mile of that same water well also have shallower casing. In all, a third of the gas wells reviewed had casing shallower than nearby water wells.
Pavillion rancher John Fenton’s water well is listed at 500 feet deep. The nearest gas well, less than a quarter-mile away, has casing that runs 1 foot deeper. Fenton has sharply criticized the investigation from the start, complaining in June that the state’s process has been secretive (EnergyWire, June 16).
King stressed in the study that many factors affect whether natural gas migrates into the water supply, including differences in pressure and underground permeability, so shallowly cased gas wells do not necessarily cause contamination. To better understand the contamination, the report recommends regular pressure testing on natural gas wells, additional data on water wells, new groundwater monitoring wells and in-depth analysis of the Wind River geologic formation underlying the Pavillion field.
Environmentalists who pushed for public release of the draft study said they would comment after having an expert review it. The WOGCC is accepting public comments until Sept. 6.
Wyoming officials are also conducting studies on water quality and disposal pits in Pavillion. The results will be sent to EPA and Encana for review.
E&E reporter Mike Soraghan contributed.