CU-Boulder study examines sources, occurrence rate of groundwater methane in

CU-Boulder study examines sources, occurrence rate of groundwater methane in Colorado’s Denver-Julesburg Basin

July 11, 2016                                                            Owen Sherwood

A new CU Boulder study shows that the rate of groundwater contamination due to natural gas leakage from fracking and horizontal drilling for oil and gas in northeastern Colorado’s Denver-Julesburg Basin is rare.

Owen Sherwood, lead author of the new research, says the greatest threat to ground water is from older wellbores.

CUT 1 “What we find is that accidents do happen but at a relatively rare rate of two cases per year over the last 20 years. It’s important to know that fracking has been going on in this area well back, starting in the 1940s and it really took off in the 1970s. (:16) It’s also important to note that ground water contamination does not appear to be linked specifically to hydraulic fracturing but rather the biggest problem is with older wellbores that were constructed in an era of looser regulatory regulations.” (:30)

The results also suggest that naturally generated methane from shallow coal seams in the region is the primary source of dissolved methane present in the area’s groundwater. Sherwood says in data dating back as far as 1988, dissolved methane was discovered in 523 of the 924 water wells sampled. However, based on a geochemical analysis, the researchers determined that 95.5 percent of that methane was naturally generated.

CUT 2 “We used data from the oil and gas regulator, the COGCC, and we were able to examine 924 individual water wells, that were sampled and analyzed for a specific set of geochemical indicators that we can use to figure out where the gas comes from. (:18) And so of those 924 wells, there were 42 wells that had this type of gas we call thermogenic gas that originates from deep geological formations.” (:29)

The new research is believed to be the most comprehensive study to date on the prevalence and sources of groundwater methane in Colorado using only public data, says Sherwood, a research associate with the Institute for Arctic and Alpine Research at CU Boulder. He says previous studies have sampled fewer oil and gas sites and/or relied on data provided by industry stakeholders.

CUT 3 “A unique aspect of this study is that we’re using data that’s provided by the state oil and gas regulator, the COGCC, and so they’ve collected all these data over the last 20 to 30 years and made it publically accessible. (:14) So anyone that’s interested in this study they can go online and find the data and scrutinize it for themselves.” (20)

The study was funded entirely by the National Science Foundation’s AirWaterGas Sustainability Research Network, which is based in Boulder, Colorado.

It was published today in the journal Proceedings of the National Academy of Sciences.

-CU-