Decades or longer may be needed to fully assess the effects of unconventional oil and gas production on the quality of groundwater used for drinking water in Arkansas, Louisiana, and Texas
A new U.S. Geological Survey study shows that unconventional oil and gas production in some areas of Arkansas, Louisiana, and Texas is not currently a significant source of methane or benzene to drinking water wells. These production areas include the Eagle Ford, Fayetteville, and Haynesville shale formations, which are some of the largest sources of natural gas in the country and have trillions of cubic feet of gas.
This is the first study of these areas to systematically determine the presence of benzene and methane in drinking water wells near unconventional oil and gas production areas in relation to the age of the groundwater. Methane and benzene, produced by many unconventional oil and gas wells, have various human health implications when present in high concentrations in drinking water.
The USGS has pioneered the ability to determine the age of groundwater. “Understanding the occurrence of methane and benzene in groundwater in the context of groundwater age is useful because it allows us to assess whether the hydrocarbons were from surface or subsurface sources. The ages indicate groundwater moves relatively slowly in these aquifers. Decades or longer may be needed to fully assess the effects of unconventional oil and gas production activities on the quality of groundwater used for drinking water,” said Peter McMahon, USGS hydrologist and study lead.
USGS scientists collecting water quality samples at a public-supply well overlying the Eagle Ford Shale production area in Texas. (Credit: Patty Ging, U.S. Geological Survey. Public domain.)
The USGS examined 116 domestic and public-supply wells in Arkansas, Louisiana, and Texas that were located as close as 360 feet to unconventional oil and gas wells. Methane was detected in 91 percent of…