By Braden Reddall
SACRAMENTO, California (Reuters) - California state legislators on Tuesday told regulators and oil industry lobbyists they wanted more information about the use of acid to increase flows in wells in a technique that is used more often in the state than the controversial fracking method.
California's century-old oil sector has come in for greater scrutiny as companies make early attempts to tap the Monterey shale, a deep formation that holds an estimated 15 billion barrels of oil - twice that of North Dakota's widely publicized Bakken shale.
Fracking - a technique that uses pressurized water to crack open rock formations and allow oil to flow to wells - may have become a better-known term because of its use around the country to extract shale gas and oil but the use of acid appears to be more extensive in California.
Oil companies in the state use hydrofluoric or hydrochloric acid to clean out well bores and to fracture solid rock. The technique is relatively old but its use has increased in the past decade.
"We have to get this right," state Senator Fran Pavley, who chairs the senate committee on natural resources and water, said at the hearing in Sacramento. "Regulators must also keep pace with changing technologies."
Pavley is working on legislation to regulate fracking, which has raised concerns around the country about contaminating water tables, and is considering broadening her focus to include acid jobs. There currently are no specific regulations on acid use in California's oilfields.
Some eight out of 10 Monterey shale wells could be completed using so-called acid jobs, she said, quoting figures cited by a company in a recent Reuters article.
"It is a public hazard," environmental consultant Robert Collier testified, explaining that acid could leak and be deadly.
Environmentalists have focused on the danger that acid jobs present to workers and want more research on potential ecological damage.
"Slow down," advised Bill Allayaud, director of government affairs at Environmental Working Group.
State regulators promised a report on acid in coming weeks but offered no figures on the extent of the practice on Tuesday.
Occidental Petroleum Corp, which is leading the way on Monterey development, said in 2011 it was mainly using acid jobs to get at the shale, and said recently that only a sixth of its California wells were fracked.
Mark Nechodom, head of the state's Department of Conservation, said there was no evidence that there was a problem to solve.
Briana Mordick, a petroleum geologist at the Natural Resources Defense Council who called for "common sense" regulation of acid, told the hearing that a 2004 paper described the use of tens of thousands of gallons of hydrofluoric acid to increase the production of one California well by nine times.
Industry representatives defended the practice, saying acid jobs had been used for decades and even welcomed greater disclosure because of their confidence in the technique.
"We use acid because it's effective," said Paul Deiro of the Western States Petroleum Association. "I'm unaware of any disasters related to this."
Many millions of people could be affected by oil development in the Monterey shale, which runs across a vast expanse of the state from Los Angeles to south of San Francisco.
Democratic Governor Jerry Brown, although considered among the nation's greenest governors for his renewable energy policies, surprised many supporters earlier this year when he voiced support for more production from the Monterey shale.
Drillers still are working out the best way to extract oil from the Monterey.
"Nobody's figured out the breakthrough technique," Robert Collier, an environmental consultant, told the hearing. "The oil companies are at the edge of what is known. There is no common body of expertise, because everybody has their own special sauce."
(Additional reporting by Rory Carroll; Editing by Peter Henderson and Bill Trott)