Article courtesy of Christin Coyne | September 15, 2014 | Weatherford | Shared as educational material
Using a new method of analysis, a team of researchers from five U.S. universities has determined that oil and gas activity, specifically faulty well integrity, led to the contamination of several water wells in the southern Parker County area.
Scientists have tied poor casing and cementing of oil and gas production wells to methane found in well water in Parker County, as well as seven areas in Pennsylvania, contradicting statements from state regulators and the industry, who claim their research shows oil and gas industry activity has not caused the issue.
One of the researchers, Dr. Avner Vengosh, professor of geochemistry and water quality at Duke, told the Democrat that scientists’ analysis indicated that the methane contamination in the Texas wells is likely the result of gas traveling into the groundwater aquifer by way of a nearby oil or gas well.
The Duke, Ohio State, Stanford, Dartmouth and University of Rochester scientists published their peer-reviewed study Monday in the Proceedings of the National Academy of Sciences.
Researchers used data from samples obtained from 20 Texas wells between December 2012 and November 2013, as well as data obtained from 113 wells in the Marcellus Shale area in Pennsylvania and New York.
“Sampling sites included wells where contamination had been debated previously; wells known to have naturally high level of methane and salts, which tend to co-occur in areas overlying shale gas deposits; and wells located both within and beyond a one-kilometer distance from drill sites,” according to researchers.
“We found eight clusters of wells — seven in Pennsylvania and one in Texas — with contamination, including increased levels of natural gas from the Marcellus Shale in Pennsylvania and from shallower, intermediate layers in both states,” said Thomas H. Darrah, assistant professor of earth science at Ohio State, who led the study while he was a research scientist at Duke.
“Our data clearly show that the contamination in these clusters stems from well-integrity problems such as poor casing and cementing,” Darrah said.
In addition to using the more conventional method of looking at hydrocarbon ratios and isotopic fingerprinting of the methane, scientists used noble gas geochemistry to trace the origins of the methane, Vengosh said, adding that alone the traditional methods were insufficient to make many of the distinctions that scientists were able to make in this study.
“This is the first study to provide a comprehensive analysis of noble gases and their isotopes in groundwater near shale gas wells,” Darrah said. “Using these tracers, combined with the isotopic and chemical fingerprints of hydrocarbons in the water and its salt content, we can pinpoint the sources and pathways of methane contamination, and determine if it is natural or not.”
Parker County wells
Of the samples taken from the 20 Texas wells, 13 samples, some from the same wells, were found to to be contaminated while 24 were found not to be, according Vengosh.
“The thing in Texas is kind of interesting and there is some misconception that people had and maybe that’s the reason why some people were so sure you don’t see contamination in Texas,” Vengosh said.
The source of the contamination in the Texas wells did not come directly from the Barnett Shale but from an intermediate source, the Strawn Formation, according to Vengosh. “That led to the confusion that people saw, ‘It’s not coming from the shale formation, the Barnett, meaning that it’s not contaminated.’ We demonstrated this is not the case.”
Vengosh said that due to the noble gas geochemistry analysis, researchers believe the methane is coming from the shallower formation, is arriving as a free gas, not naturally occurring, and is probably leaking into the space between the shale gas well casing and the Strawn Formation, escaping into the wells and then out into the groundwater aquifer.
“We do see methane in the background [naturally occuring] and we see that as coming from the regional flow from the Strawn,” Vengosh said. “But the noble gas that is coming with that is very much different than the noble gas from the the free gas contamination from the shale gas well.”
Scientists saw similar phenomena in Pennsylvania, as well, according to Vengosh.
Vengosh said their findings showing contamination from an intermediate source such as the Strawn Formation are not unique.
A similar study conducted in Canada by a University of Alberta geologist found that many of the wells in Alberta are showing gas contamination from intermediate sources, rather than the deep oil or gas formation.
The scientists’ findings differ from conclusions reached by the Texas Railroad Commission, the state’s oil and gas industry regulator, earlier this year.
“Our staff is currently reviewing the study, which will take a period of time to complete, and [has] no comment at this time on the study,” RRC spokeswoman Ramona Nye said Monday.
In May, the commission issued a report on the Parker County water wells, some of which have had increasing concentrations of methane, stating that isotopic data was inconclusive about the origin of the gas but ruled out Barnett Shale gas production as a cause of the natural gas in the water wells.
The commission found that the natural gas in complainants’ water wells may be attributed to natural migration from the shallow Strawn Formation and exacerbated by water well construction practices.
Range Resources also disputed the conclusions reached by the scientists.
“Exhaustive studies have clearly demonstrated that no aspects of Range’s activities caused or contributed to the long-standing and well-documented fact that gas is naturally occurring in the Trinity aquifer,” Range Resources spokesman Matt Pitzarella said. “While we have not had the opportunity to study the report, the extensive testing conducted by Range and the Texas Railroad Commission prove that the two Range wells could not have been the source of the gas in any water wells, nor did any other aspects of our work. Importantly, there was existing oil and gas drilling, including shallow Strawn formation wells in the area, as well as water wells that penetrated the Strawn and that could have been observed in their analysis.”
Range Resources is suing Parker County homeowner Steve Lipsky, who can light his water on fire due to methane levels in his well, for defamation after he filed a lawsuit accusing the company of causing the contamination of his water well. That case is ongoing.
The U.S. Environmental Protection Agency issued an emergency order against Range Resources in December 2010 and, during a two-year investigation and legal battle, later reached an agreement with Range Resources, withdrew the order and halted the investigation. A group of organizations earlier this year asked the EPA to reopen the investigation.
Scientists believe regulators and the oil and gas industry can take steps to prevent contamination issues.
“The good news is that most of the issues we have identified can potentially be avoided by future improvements in well integrity,” Darrah said.
Tools to identify when contamination has occurred have been lacking, according to Vengosh.
Though researchers are not saying this water contamination is a problem everywhere, one of the conclusions is a much more tedious and robust monitoring system is required to assess the magnitude of what scientists are finding, Vengosh said.
There are several simple, common sense measures that could be taken to reduce the impact of leaking methane, according to Vengosh.
In areas that are to be developed, Vengosh suggested a buffer zone between drinking water wells and a drilling site.
Scientists haven’t seen an effect on drinking water outside of a kilometer distance, he said.
In addition, he recommended independent inspections on the integrity of the wells so that if there is a leak, it will be identified.