PITTSBURGH -- A landmark federal study on hydraulic fracturing, or fracking, shows no evidence chemicals from the natural gas drilling process moved up to contaminate drinking water aquifers at a western Pennsylvania drilling site, the Department of Energy told The Associated Press.
After a year of monitoring, the researchers found the chemical-laced fluids used to free gas trapped deep below the surface stayed thousands of feet below the shallower areas that supply drinking water, geologist Richard Hammack said.
Although the results are preliminary -- the study is still ongoing -- they are a boost to a natural gas industry that has fought complaints from environmental groups and property owners who call fracking dangerous.
Drilling fluids tagged with unique markers were injected more than 2,400 metres below the surface, but were not detected in a monitoring zone 900 metres higher. That means the potentially dangerous substances stayed about a kilometre and a half away from drinking water supplies.
"This is good news," said Duke University scientist Rob Jackson, who was not involved with the study. He called it a "useful and important approach" to monitoring fracking, but cautioned the single study doesn't prove fracking can't pollute, since geology and industry practices vary widely in Pennsylvania and across the nation.
The boom in gas drilling has led to tens of thousands of new wells being drilled in recent years, many in the Marcellus Shale formation that lies under parts of Pennsylvania, New York, Ohio and West Virginia. That's led to major economic benefits but also fears the chemicals used in the drilling process could spread to water supplies.
The mix of chemicals varies by company and region, and while some are openly listed, the industry has complained disclosing special formulas could violate trade secrets. Some of the chemicals are toxic and could cause health problems in significant doses, so the lack of full transparency has worried landowners and public health experts.
The study done by the National Energy Technology Laboratory in Pittsburgh marked the first time a drilling company let government scientists inject special tracers into the fracking fluid and then continue regular monitoring to see whether it spread toward drinking-water sources. The research is being done at a drilling site in Greene County, which is southwest of Pittsburgh and adjacent to West Virginia.
Eight new Marcellus Shale horizontal wells were monitored seismically and one was injected with four different man-made tracers at different stages of the fracking process, which involves setting off small explosions to break the rock apart. The scientists also monitored a separate series of older gas wells that are about 900 metres above the Marcellus to see if the fracking fluid reached up to them.
The industry and many state and federal regulators have long contended fracking itself won't contaminate surface drinking water because of the extreme depth of the gas wells. Most are more than 1.5 km underground, while drinking water aquifers are usually within 150 to 300 metres of the surface.
Kathryn Klaber, the CEO of the industry-led Marcellus Shale Coalition, called the study "great news."
"It's important that we continue to seek partnerships that can study these issues, and inform the public of the findings," Klaber said.
While the lack of contamination is encouraging, Jackson said he wondered whether the unidentified drilling company might have consciously or unconsciously taken extra care with the research site, since it was being watched. He also noted other aspects of the drilling process can cause pollution, such as poor well construction, surface spills of chemicals, and wastewater.
-- The Associated Press