Fracking hasn’t unleashed an oil production boom in California, at least not yet.

Could acid?

Companies trying to pry oil from a vast shale formation beneath Central California have been pumping powerful acids underground to dissolve the rock and free the petroleum within.

And there are hints that the process, known as “acidizing” a well, may work better than hydraulic fracturing in California’s Monterey Shale, estimated to hold 15.4 billion barrels of oil.

“There’s a lot of discussion around the Monterey Shale that it doesn’t require fracking, that acidizing will be enough to open up the rock,” said Chris Faulkner, chief executive officer of Breitling Oil and Gas. “I think it could be a way to unlock the Monterey. And people need to understand that this is a huge resource that could mean a lot of jobs.”

For all its potential, acidizing in California remains a bit of a mystery. State regulators don’t keep tabs on how often oil companies use the process. Nor have they studied its potential risks in depth.

Most oil companies will say little in public about acidizing. They don’t want to reveal too much information to their competitors, each of which has its own methods and chemical formula. They also don’t want to draw the attention of the state’s powerful environmental lobby.

But environmentalists have noticed anyway. So have California lawmakers.

State regulations

State Sen. Fran Pavley has included acidizing in a bill that initially focused on regulating fracking. Her bill, SB4, would require companies to obtain a specific permit from the state before acidizing or fracking a well. It also would commission a study of the threats each oil-production technique could pose to the environment.

“It’s one of those things where the more you read, the more questions you have,” said Pavley, D-Agoura Hills (Los Angeles County). “I’m concerned that the narrow focus on fracking isn’t sufficient to protect health and safety.”

Oil industry representatives insist acidizing can be done safely. “We use acid because it’s effective,” Paul Deiro, a lobbyist for the Western States Petroleum Association, told legislators at a hearing convened by Pavley in June. “And we handle it safely. I’m unaware of any disasters related to that.”

State officials still don’t have a clear idea how many wells in California have been stimulated with acid. The state agency that regulates oil drilling – the Division of Oil, Gas and Geothermal Resources, within the California Department of Conservation – doesn’t keep track, although it might in the future. And while many of the companies fracking in California post information about fracked wells online, using a nationwide website called FracFocus, they don’t do the same for acidized wells.

And yet the companies exploring the Monterey Shale have dropped occasional hints.

Occidental Petroleum Corp., which controls more Monterey Shale property than any other company, has told Wall Street analysts that it relies more on acidizing than fracking to tap California’s shale formations.

“It’s mainly acid-jobs driven, and we’re just simply treating these wells in larger intervals with more acid,” said William Albrecht, president of the Los Angeles company’s oil and gas operations in the Americas, during a 2011 conference call with analysts.

Occidental declined to comment for this story, referring questions to the petroleum association.

Drillers have been pouring acid down oil wells for more than a century, using it to dissolve the underground drilling debris that surrounds new wells. Acid can also clean out hydrocarbon deposits that gum up older wells.

In the Monterey Shale, however, oil companies are using larger amounts of hydrofluoric and hydrochloric acids to open tiny channels in the rock around each well. Those channels allow oil trapped within the rock to flow into the well.

Powerful corrosive

Fracking also creates channels within shale, but does so by blasting the rock with a high-pressure mixture of water, sand and chemicals. Acidizing doesn’t require high pressure or sand. It can, however, be combined with fracking in a process called fracture acidizing, or acid frack.

Hydrofluoric acid in particular is a powerful corrosive, capable of eating through steel as well as rock. So companies blend it with water and other chemicals to protect their wells. Mark Nechodom, director of the Department of Conservation, said drillers in California have used acid concentrations as high as 15 percent, although it’s typically in the single digits.

Companies go out of their way to keep the exact composition of their acidizing fluids secret. At an industry conference in Bakersfield this spring, energy policy consultant Robert Collier watched oil company representatives try to discuss acidizing without divulging their own processes or plans.

“They were trying to get information from each other without giving any up,” said Collier, a former Chronicle journalist who has written several reports about acidizing for the Next Generation think tank. “People weren’t talking about exact percentages, their formulas. You don’t give up your special sauce.”

Hydrofluoric acid can damage lungs and cause severe skin burns. Above 67 degrees, it can form a vapor cloud that stays near the ground, according to Collier. A hydrofluoric acid accident last September at a South Korean chemical plant killed five people.

No serious accidents

State officials say they are unaware of any serious accidents involving acidizing in California oil wells. Nor have they seen cases of acid from a well seeping into groundwater.

“At least in our reading of current well histories or reporting, there’s no evidence that we currently have a problem to solve,” Nechodom told Pavley and other state legislators at the acidizing hearing in June. “But I think there’s good purpose in taking a hard look at this to see if perhaps we have missed something or if we should add something to our regulatory oversight.”

• See good graphic comparing a “Typical Shale deposit” to “Monterey Shale”