Due to adjustments made by oil and natural gas service companies, Democratic leaders on the House Energy and Commerce Committee Tuesday said 500,000 gallons more of diesel fuel and fluids were used in hydraulic fracturing (fracking) between 2005 and 2009 than were previously reported.

Two companies, Frac Tech Services and Weatherford, "have informed the committee that they inadvertently provided inaccurate data in response to the committee's request for information on the type and volume of products used in hydraulic fracturing between 2005 and 2009," resulting in an underestimation of diesel fuel used in fracking by more than 500,000 gallons, wrote Rep.Henry Waxman of California, ranking member of the energy panel, and Reps. Edward Markey of Massachusetts and Diana DeGette of Colorado, in a letter to Administrator Lisa Jackson of the Environmental Protection Agency.

In August Frac Tech informed the committee that it had used almost 2.4 million gallons of a product that contains at least 20% diesel fuel. Previously the company reported to the House panel that it had not used diesel fuel between 2005 and 2009.

Weatherford has incorrectly stated that it had used a product that had diesel fuel components when it didn't, the committee said. "As a result of this error, the information originally provided to the committee by [Weatherford] overstated the company's use of products containing diesel by nearly 1.9 million gallons."

All told, the service companies injected 32.7 million gallons of diesel fuel or fracking fluids containing diesel fuel during the 2005-2009 period, compared to the 32.2 million gallons that were reported in February, a committee spokeswoman said.

Waxman, when he was chairman of the House energy panel in 2010, and Markey and DeGette opened a year-long inquiry into the potential health and environmental risks associated with the use of diesel fuel in fracking of shale gas, and reported the results of their probe in February (see Shale Daily, Feb. 1).

Fluids containing diesel fuel were injected in 20 states, according to the committee. Texas took the lead, with 16.7 million gallons being injected during the 2005-2009 period. It was followed by Oklahoma (3.2 million gallons); North Dakota ( 3.13 million gallons); Wyoming (2.95 million gallons) and Louisiana (2.92 million gallons).

BJ Services used the most diesel fuel and fluids containing diesel fuel (more than 11.5 million gallons), followed by Halliburton, which used 7.2 million gallons. Other large users of diesel fuel or fluids included: RPC (4.3 million gallons), Sanjel (3.6 million gallons), Frac Tech (2.6 million gallons) and Key Energy Services (1.6 million gallons).