Caves create long-term water contamination concerns

Caves create long-term water contamination concerns by Gayathri Vaidyanathan, September 11, 2012, E&E News
Rancher Stacey Mills realized something was wrong when his cattle started falling sick and dying. Half of his 70,000 acres in the southwestern corner of New Mexico drew from an aquifer that had the cleanest, sweetest water. But tests in 2006 revealed that his water well was contaminated with brine. A month earlier, EOG Resources Inc. had begun disposing of brine, a waste product of drilling oil and gas wells, in an abandoned oil well nearby. It was never established that the EOG brine had polluted the aquifer; the leak was sealed before officials tested for links between the well and the aquifer, Mills said. An EOG spokeswoman stressed that tests did not show communication between the brine well and aquifer. But in an effort to be a good neighbor, the company built Mills a new water well on his property and the infrastructure to go along with it.

The takeaway from the incident for James Goodbar, who leads the Bureau of Land Management’s caves and karst resources program, was that oil wells do fail after a few decades. A rash of new applications to drill had been cropping up since 2004 in southwestern New Mexico, in the Permian Basin oil and gas deposits. The region contains karst, a type of geology composed of rocks that dissolve in mildly acidic water over time, creating grottos that’ve made New Mexico a destination for cavers. Water flows quickly through these underground drainage systems, and a contaminant spilled in one place can end up in water wells miles away. Spills and leaks, if they happen, are harder to contain and clean up in karst areas than elsewhere.

Goodbar wanted to make sure that oil and gas wells do not leak, a century later, into the aquifers that supply Carlsbad, N.M., with its water supply. Other industries have contaminated springs and wells in karst terrain before. Now, with the new industrialization of America’s oil and gas, scientists worry about similar contamination as more applications to drill on karst come in.

BLM embarked on a series of experiments in New Mexico to justify its special casing rules and prove there are links between oil wells and aquifers. Goodbar and his colleagues asked oil companies to include certain nontoxic dyes in their drilling fluid. The participating companies drilled 23 wells in 2007. If any drilling fluid escaped the well bore and migrated to a distant water well, the dye would theoretically be recovered there. The scientists placed dye-detection traps in three springs, two domestic water wells and the Capitan Reef aquifer that supplies Carlsbad’s water. While drilling, five operators lost their drilling fluid. The scientists later found traces of the injected dye in traps in some of the water wells. The study “was to scientifically prove, without a shadow of a doubt, that there was a connection between oil and gas drilling and our water supplies,” Goodbar said. …

In Kansas, corrosion of the casing of a brine disposal well allowed the brine to escape into the surrounding karst for many years. The brine eventually dissolved enough of the rocks to cause the Panning Sinkhole in 1959. … Harold Parsons, a geologist formerly with the state’s Department of Environmental Protection, carried out some dye tracer studies to explore the paths groundwater takes in his county. Monroe County has entered into a memorandum of understanding with the oil company, asking it to triple case wells and use high-grade steel. The West Virginia Legislature also recently updated its drilling laws, suggesting additional well casings may be needed in karst areas. Even so, Parsons is not certain the threat has been addressed. The area is too rural to get piped water, so groundwater contamination would be a problem, he said. His tracer studies revealed that some sinkholes that resemble innocuous, littered ditches link directly to water supplies. “Even if you did triple casing, if those fail for some reason, if they weren’t properly installed, for example, they could fail and you may have the same situation,” Parsons said. “If a truck hauling frack fluid or any kind of chemical wrecks on the road and spills its contents into a sink that goes into the underground water system, then we’ve got a problem.”

“Our aquifers didn’t form overnight; they took at least a million years to form through geologic time and erosion,” said Paul Rubin, hydrogeologist at the environmental consulting firm HydroQuest in New York. “And there’s no reason to believe that they shouldn’t operate, if we don’t contaminate them, for the next million years.” [Emphasis added]

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