Scientists Create Inexpensive, Less Intensive Protocol to Detect Methane
Penn State researchers have implemented a new testing protocol that utilizes existing water chemistry tests. This implementation of previously used tests takes advantage of their affordability in a unique protocol that aims to help regulators and scientists detect sites showing evidence of new methane gas leaks that result from oil and gas drilling.
Testing protocols that were previously described in the Proceedings of the National Academy of Sciences and administered to a larger dataset of three different domestic water wells that had been affected by the fossil fuel industry. The researchers aimed to find the percentage of water wells that showed certain chemical changes indicating new methane contamination typical of drilling and fossil fuel extraction.
"We expected to see few sites, less than 1%, showing evidence of new methane," said Tao Wen, a postdoctoral scholar in the Earth and Environmental Systems Institute at Penn State. "We found 17 out of 20,751 samples, or about 0.08 %, that showed possible signs of methane contamination when those samples were collected."
The scientists classified the water samples into five types. The two types that were defined as samples likely impacted by new methane contained high levels of sulfate and methane and either low or high iron levels. Researchers classified low-methane samples, samples with methane measuring less than 10 parts per million, as low priority. The other two types not impacted by new methane contained large methane levels and either freshwater and low sulfate levels, indicating the methane had been there some time, or high salts, suggesting the methane was naturally derived. They published their findings in the journal Environmental Science & Technology and for the first time made public the datasets.
"It's not uncommon to see methane in groundwater in the Marcellus shale and other shale plays," Wen said. "Also, if methane had been in the groundwater for a long time, bacteria would have reduced the iron and sulfate. The reduced forms would have precipitated as iron sulfide or pyrite."
State legislation mandates oil and gas companies except responsibility for methane leaks that affect wells within that 2,500-foot area. Of the 17 samples that tested positive for new methane, 13 came from the northeast region. Not one of the positive samples came from sites within 2,500 feet of known problematic gas wells. This could indicate that methane may migrate farther than previously thought, assuming the new methane was derived from these known problematic gas wells. In order to demonstrate more certainty of the new methane derivation, intensive field investigations would be needed.
"We focus on the Marcellus shale, but this testing protocol has the potential to be applied to other shale plays in the United States and other countries," he said. "It can benefit the global community."
According to Wen, future applications of this testing protocol can serve as a screening tool for methane contamination and narrow the window for more comprehensive analyses.