WASHINGTON, April 18 (Reuters) - U.S. environment regulators are expected to finalize long-delayed rules Wednesday that aim to slash smog-forming emissions from hydraulic fracturing, or fracking, at oil and natural gas wells.
The Environmental Protection Agency is under court order to finalize the rules that have been delayed four times since September. It said Wednesday it will hold a press conference call at 1 p.m. EDT (1700 GMT) to discuss an announcement on clean air.
The Obama administration is attempting to balance its support for an industry that could help the United States become a major exporter of natural gas with how to address concerns about its safety.
Environmentalists and health groups have complained that fracking operations near schools and homes can harm air and water supplies.
A draft rule the agency issued last July sought to cut emissions of so-called volatile organic compounds that contribute to smog by nearly 25 percent across the oil and gas industry and by 95 percent from wells using the controversial technique of fracking.
The standards have caused a dispute among environmentalists, who say equipment that could be added to drilling rigs would only add minor costs to drilling, and energy companies who say the costs are much higher and the equipment is not yet fully available.
The American Petroleum Institute, an industry group, has said the equipment to capture emissions in the first few days after fracking is completed could cost about $180,000 per well.
Environmentalists say the number is much less. In addition, some methane is also captured by the so-called green completion systems that could be sold to help pay for the equipment, even with natural gas at very low prices, they said.
Companies including Chesapeake Energy and Exxon Mobil could be forced by the rules to invest in pollution control technologies.
The EPA said in July the standards would rely on existing technologies to cut emissions that can also cause cancer, while supporting the expansion of oil and gas production.