A schematic of possible migration pathways of contaminants, water-based and gas-phase, into the bedrock aquifer from adjacent faulty oil or gas wells.
There’s no evidence of water-based contaminants seeping into drinking water wells atop a vast oil and gas field in northeastern Colorado, according to Colorado State University scientists working to protect and inform citizens about the safety of their water.
Ken Carlson, professor of civil and environmental engineering, has led a series of studies analyzing the impact of oil and gas drilling on groundwater in the 6,700-square-mile Denver-Julesburg Basin, which extends north-south from Greeley to Colorado Springs, and east-west from Limon to the foothills.
Colorado Water Watch
The studies have been performed under the auspices of the Colorado Water Watch, a state-funded effort begun last year for real-time groundwater monitoring in the Denver-Julesburg Basin. The basin shares space with more than 30,000 active or abandoned oil and/or natural gas wells. The CSU researchers primarily looked at the 24,000 producing and 7,500 abandoned wells in the Wattenberg Field, which sits mainly in Weld County.
“We feel that our results add to our database of knowledge,” Carlson said. “There isn’t a chronic, the-sky-is-falling type of problem with water contamination.”
Wells show methane contamination
That isn’t to say that some of the water wells in the basin over the Wattenberg oil and gas field aren’t compromised. Carlson’s team found that 2 percent of their sampled wells showed seepage of oil- and gas-related methane – a flammable greenhouse gas that’s the main component in natural gas.
And that’s not good, Carlson said. Methane, a concern for climate change emissions, can also be explosive (which is why coal mines blow up, and why the movie “Gasland” portrayed flaming taps). But it’s not toxic, and isn’t a huge factor in terms of drinking water safety. It also is found in large quantities in the basin from naturally occurring, biogenic sources.
With regard to the really bad stuff – the bariums, chromiums and other soluble contaminants that people have been worried about getting into their water – Carlson’s team didn’t find any.
Likely culprit: Bad casings
Their studies strengthen the theory that thermogenic (originating from oil and gas formations) methane contamination is most likely due to stray gas moving along the outside of compromised well casings in and around the aquifers. Well casings are the cement and steel housing around the production tubing of the oil rig. That tubing penetrates the ground, straight through the aquifer, and into the oil- and gas-rich sediment thousands of feet below.
“My guess is that most of the thermogenic methane-contaminated wells we see out there are 10 to 30 years old,” Carlson said. “Well casing requirements and monitoring have tightened up significantly since the 2009 regulations.”
The latest studies were published in Environmental Science and Technology, and in Water Research.