In a statement, the EPA listed the nine companies as BJ Services, Complete Production Services, Halliburton, Key Energy Services, Patterson-UTI, PRC, Schlumberger, Superior Well Services, and Weatherford.
The agency said the data requested "is integral to a broad scientific study now underway by EPA."
In 2009, Congress directed the agency to conduct a study to determine whether fracking has an impact on drinking water and the public health of nearby residents.
"This scientifically rigorous study will help us understand the potential impacts of hydraulic fracturing on drinking water," EPA Administrator Lisa Jackson said.
"By sharing information about the chemicals and methods they are using, these companies will help us make a thorough and efficient review of hydraulic fracturing and determine the best path forward," she added.
In a statement, Halliburton said it had not yet received a formal request from the EPA regarding additional information on fracking fluids, "however, if we are asked, we will of course fully cooperate with their request."
The company added that it "supports and continues to comply with state, local and federal requirements promoting the forthright disclosure of the chemical additives that typically comprise less than one-half of 1% of our hydraulic fracturing solutions."
Whether or not service companies should be compelled to disclose the chemical composition of fracking fluids has recently become a hot-button issue as gas producers expand their efforts in shale basins across the US, many of which have little prior experience with gas and oil operations.
China Chemical Weekly: http://news.chemnet.com/en/detail-1411716.html
