PITTSBURGH (AP) - A landmark federal study on hydraulic fracturing, or fracking, shows no evidence that 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 that 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 the first independent look at whether the potentially toxic chemicals pose a threat to people during normal drilling operations. But DOE researchers view the study as just one part of ongoing efforts to examine the impacts of a recent boom in oil and gas exploration, not a final answer about the risks.
Drilling fluids tagged with unique markers were injected more than 8,000 feet below the surface at the gas well bore but weren't detected in a monitoring zone at a depth of 5,000 feet. The researchers also tracked the maximum extent of the man-made fractures, and all were at least 6,000 feet below the surface.
That means the potentially dangerous substances stayed about a mile away from surface drinking water supplies, which are usually at depths of less than 500 feet.
"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 he cautioned that the single study doesn't prove that 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 that 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 that 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.
Over the last four years the debate over fracking chemicals has attracted tremendous attention from state and federal agencies, public health experts, and opponents of fracking. Yet while many people have focused on the potential threat from the chemicals, experts have come to believe that more routine aspects of the drilling process are more likely to cause problems. Poor well construction that allows excess gas to escape, spills of chemicals or other fluids that take place at the surface, and disposal of wastewater are all issues of concern.
Jackson said most of the problems that the Duke researchers have seen have been related to well construction, not fracking chemicals.
The study done by the National Energy Technology Laboratory in Pittsburgh marked the first time that 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 Marcellus Shale 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 3,000 feet above the Marcellus to see if the fracking fluid reached up to them.
The industry and many state and federal regulators have long contended that fracking itself won't contaminate surface drinking water because of the extreme depth of the gas wells.