Alex Mills
By Alex Mills
Three important studies dealing with oil and gas drilling procedures, including hydraulic fracturing, were released in September apparently clearing the fracturing process from allegations that it has caused contamination of groundwater wells.
One of the studies conducted by the Department of Energy found no evidence the wells fractured in Pennsylvania caused gas or fluid migration upward into water wells.
Researchers from Ohio State University, Duke University and the University of Rochester released their study that concluded hydraulic fractured wells in the Marcellus formation and Texas’s Barnett Shale were not the cause of water well contamination.
The two studies were not coordinated, but the DOE study examined the drilling process from the surface to total depth and the Ohio State study took the opposite approach from the bottom of the well to the top.
The third study, released by the University of Texas at Arlington, dealt with the quality of water in aquifers overlying the Barnett Shale. It tested 100 private drinking water wells and found some levels of contamination that exceeded the Environmental Protection Agency’s Drinking Water Maximum Contaminant Limit (MCL), but it did not state that drilling and production activities were the cause. It did state that 29 percent of the samples occurred with 3 kilometers of an active natural gas well.
DOE Study
The DOE monitored drilling activity that included hydraulic fracturing for 18 months using tracer fluids, seismic monitoring and other tests to create a detailed report on what happens to fluids during this process.
The report stated that researchers found that fracturing fluids stayed more than 5,000 feet below drinking water supplies.
Ohio State
Researchers analyzed 113 and 20 samples from drinking water wells overlying the Marcellus and Barnett Shales, respectively. They documented fugitive gas in eight clusters of domestic water wells. “Gas geochemistry data implicate leaks through annulus cement (four cases), production casing (three cases), and underground well failure (one case) rather than gas migration induced by horizontal drilling or hydraulic fracturing deep underground.”
UT Arlington
The study admits that “there is very little information on groundwater quality prior to natural gas extraction activities.” It notes that 16,743 wells have been drilled in the Barnett Shale as of May 2013.
“Natural gas extraction in the Barnett Shale formation should have little effect on the overlyng Trinity and Woodbine aquifers as they are separated from the shale formation by over a thousand meters of impermeable rock,” the study said.
“Our results show elevated concentrations of constituents in the Barnett Shale region; however, we are unable to determine the ultimate source of these elevated concentrations directly,” the study stated.
However, one of the researchers, Dr. Zacariah Hildenbrand, a UTA biochemist, was quoted in the Denton Record Chronicle as saying: “This is indirect evidence that drilling does affect the water.” Dr. Hildenbrand’s comment conflicts with the conclusions of the study.
The UTA study creates more questions. Why did the study not include any information about the integrity of the natural gas wells? When were the wells drilled? Did they meet state regulatory requirements? All of this information would have a direct bearing on Dr. Hildenbrand’s assumption that “drilling does affect the water.”
Groundwater contamination more likely comes from agriculture use or gas migration from shallow formations with naturally occurring methane. These causes are much closer to groundwater sources that are generally 50 to 200 feet deep than they are to natural gas wells that are 5,000 to 8,000 feet deep. The study itself alludes to this: “Arsenic, strontium, and barium all showed significant negative correlations with the depth of private water wells. This could be due to contact with surface sources as the highest concentrations of arsenic and other compounds occur at the shallowest depths of private water wells.”
The study did not detect any salt water in the contaminated wells, which would be present if the contamination came from a natural gas well.
Alex Mills is President of the Texas Alliance of Energy Producers. The opinions expressed are solely of the author.
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