Natural gas found in North Texas water wells did not come from the Barnett Shale but rather the gas-bearing Strawn formation, which is closer to the surface, hearing examiners at the Railroad Commission of Texas (RRC) said in a report released Monday. If accepted by commissioners, the finding would exonerate Range Resources Corp., which had been accused of contaminating the wells with its Barnett drilling activities.
The Range gas wells in question are known as the Butler and Teal wells; the water wells with methane in them are called the Perdue and Lipsky wells, after their owners. RRC investigators tested water wells within 3,000 feet of the surface location of the Butler and Teal gas wells except in cases where homeowners would not allow it.
"In the samples, methane concentrations ranged from non-detect to almost 3 parts per million (ppm)," the RRC hearings examiners' report said. "The Perdue water well had the highest methane concentrations, at 2.8 ppm. The Perdue well is the deepest water well in the area, extending about 100 feet into the Strawn. The Lipsky well had a methane concentration of 2.3 ppm, the second highest concentration found. The concentrations in the various water wells do not demonstrate any type of plume, which would be expected if the gas was from a single source. Instead, the concentrations in the wells vary randomly over the area.
"...If Barnett Shale gas were migrating upwards and communicating to shallower zones, some component of Barnett Shale gas would have been present in the bradenhead samples of the Teal and Butler wells. Further, the gas found in most of the water well samples has differing degrees of biodegradation, indicating that gas had seeped into the aquifer over geologic time and not in a single event."
The RRC began its investigation of the water well contamination last August, and in October the U.S. Environmental Protection Agency (EPA) began its own investigation. EPA in December issued an emergency order to Range and ordered the company to ensure that its Butler Unit and Teal Unit production facilities -- thought by EPA to be the cause of the natural gas in the water wells -- "pose no imminent and substantial endangerment to public health through methane contamination of an underground source of drinking water [see Shale Daily, Jan. 21; Dec. 9, 2010]."
State regulators were more skeptical than EPA that Range caused the water well contamination, and commissioners spoke out against EPA for stepping into what they considered to be a state regulatory matter.
Last month RRC staff told the hearing examiners that the Strawn formation was the most likely cause of the water well contamination (see Shale Daily, Feb. 10).
"We're not surprised by the report," said Range spokesman Matt Pitzarella Tuesday. "It's consistent with every technical expert and scientist who has examined this issue, including those at the EPA, and they've all concluded that this is a matter of Mother Nature, unrelated to Range's activities and one that has been effectively managed by state regulators, local businesses and private citizens in a safe and effective manner. People in Parker, Hood and surrounding communities deserve the right to know that their water is safe and secure, and the facts are not out there for anyone to see."
According to the hearing examiners, natural gas is no stranger to water wells in the area, whether residents realize it or not.
"Prior to the drilling of the Teal and Butler wells in 2009, there is significant evidence of shallow gas production within a 2 1/2-mile radius of the wells," the hearing examiners' report said. "The Strawn formation directly underlies the Cretaceous formation, which is the aquifer in the area. Water well records indicate that numerous water wells penetrated the Strawn formation, while numerous others are completed within 25 feet of the top of the Strawn. In addition to gas produced in the numerous water wells, several gas wells were completed in the Center Mill (Strawn) Field approximately one mile to the southeast of the Butler and Teal wells. These wells produced gas in the mid-1980s from the Strawn, with depths ranging from 358 feet to 426 feet."