Ellen Knickmeyer

SAN FRANCISCO: Voters in three coastal California counties will cast ballots Tuesday on whether to ban fracking and other intensive oil production, even as slumping prices globally are leading companies to start to scale back on production.

Chevron, ExxonMobil and other oil companies have donated about $7 million to try to defeat the fracking bans in Santa Barbara, San Benito and Monterey counties. In Santa Barbara and San Benito counties, the ballot measures would ban not only fracking — a method of injecting water and chemicals into rock at high pressure to force out oil — but one of the most commonly used drilling methods in the state, steam injection.

None of the three counties currently is known to host onshore fracking. That has led some opponents of the fracking bans to argue the vote is no more necessary than banning ice-fishing in the temperate, coastal counties.

However, all three counties lie on the Monterey Shale, a vast petroleum deposit earlier estimated to hold more than 10 billion barrels of oil. Interest in the formation faded earlier this year when the federal government slashed its estimate of the formation’s recoverable oil to 600 million barrels, acknowledging the region’s mangled geology made extracting the rest of the oil financially unfeasible, at least for now.

Nationally and internationally, increasing production of North America’s shale oil has driven oil prices down to about $80 a barrel, a one-quarter drop since mid-summer. Campaigners for the California fracking bans argue oil companies will want to use fracking and other stepped-up methods to go after the area’s shale deposits whenever oil prices rise again.