The Environmental Protection Agency subpoenaed energy giant Halliburton Tuesday, seeking a description of the chemical components used in a drilling technique called hydraulic fracturing.
The EPA said it issued the subpoena after Texas-based Halliburton refused to voluntarily disclose the chemicals used in the controversial drilling practice, also known as "fracking." Halliburton was the only one of nine major energy companies that refused the EPA's request.
The agency said the information is important to its study of fracking, in which crews inject millions of gallons of water, mixed with sand and chemicals underground to force open channels in sand and rock formations so oil and natural gas will flow.
The EPA is studying whether the practice affects drinking water and the public health.
A Halliburton spokeswoman said the company was disappointed by the EPA's action.
"Halliburton welcomes any federal court's examination of our good-faith efforts with the EPA to date," said spokeswoman Teresa Wong.
The subpoena is the latest bad news for Halliburton, which has been under fire for its role in the BP oil spill in the Gulf of Mexico. Investigators for a presidential panel say the company pumped faulty cement into the well that later blew out, killing 11 people and spewing more than 200 million gallons of crude oil.
The company also has faced renewed criticism over a provision in the 2005 energy law that prevents the EPA from regulating fracking. The exemption is commonly called the "Halliburton loophole," in reference to the company's pioneering role in fracking. An energy task force convened by former Vice President Dick Cheney, a onetime Halliburton CEO, had urged the EPA exemption.
Wong said the EPA's request, made in September, was overly broad and could require the company to prepare about 50,000 spreadsheets.
"We have met with the agency and had several additional discussions with EPA personnel in order to help narrow the focus of their unreasonable demands so that we could provide the agency what it needs to complete its study of hydraulic fracturing," Wong said. Halliburton turned over nearly 5,000 pages of documents last week, she said.
Drilling companies have largely sought to protect their chemical formulas, calling them proprietary. Environmentalists are concerned that the chemicals, some of them carcinogens, will taint underground water supplies.
A 2009 report prepared for the Energy Department said sand and chemicals typically account for less than 2 percent of fracturing fluids, with water making up 98 to 99.5 percent.
The EPA is taking a new look at fracking as gas drillers swarm to the lucrative Marcellus Shale beneath Pennsylvania, New York, West Virginia and Ohio and blast into other shale formations around the country.
Fracking is exempt from federal regulation. The process is touted as the key to unlocking huge reserves of clean-burning natural gas.
Supporters say the practice is safe, noting that it is done thousands of feet below ground, much deeper than most water sources. They also point out that authorities have yet to link fracking to contaminated drinking water.
The EPA said in March it will study potential human health and water quality threats from fracking. Initial results are expected in 2012.
The EPA said eight other national and regional drilling companies either fully complied with its Sept. 9 request or made unconditional commitments to provide information soon. The other companies are BJ Services Co.; Complete Production Services; Key Energy Services; Patterson-UTI; RPC, Inc.; Schlumberger; Superior Well Services Inc.; and Weatherford. All but RPC and Superior are based in Houston. RPC is based in Atlanta and Superior in Indiana, Pa.