By Rory Carroll
SAN FRANCISCO (Reuters) - California Governor Jerry Brown, a prominent environmentalist, said on Wednesday the state should consider the use of "fracking" technology to develop its massive shale oil reserves and reduce reliance on imported oil.
Brown, who led California's efforts to curb climate change by reducing greenhouse gas emissions, cautioned the state would develop rules to preserve the environment, and said many questions on the technology were still to be answered.
"We want to get the greenhouse gas emissions down, but we also want to keep our economy going. That's that balance that's required," he said at an event to announce the approval of three new renewable energy projects.
U.S. oil and natural gas production has soared on the back of technological advances based on fracking, which involves injecting water and chemicals to fracture rock formations and unlock deposits that are untappable by conventional means.
While most production so far is from deposits has come from states in the U.S. interior, California hosts the vast Monterey shale deposit, which the U.S. Energy Department has estimated could hold upward of 15 billion barrels of oil, about 64 percent of the nation's total shale oil resources.
Because of its geology, the Monterey shale is particularly deep and hard to reach, presenting challenges to oil companies hoping to extract its huge resources.
Environmental groups have also taken a hard line against fracking, saying it has the potential to pollute drinking water supplies.
Some groups have called for an outright ban on the practice in California, and state lawmakers have introduced a flurry of bills that seek to regulate the industry.
Brown said any decisions on fracking would be based on science and common sense, and on a process that "listens to people but also wants to take advantage of the great opportunities we have."
"The fossil fuel deposits in California are incredible, the potential is extraordinary," he said. "But between now and development lies a lot of questions that need to be answered."
Even if California cut its dependence on oil altogether, it could still make sense to continue producing oil if it can be sold elsewhere, he added.
If the Monterey deposit was fully developed, it could produce about 600,000 barrels of oil a day, doubling the state's current production levels and eliminating all foreign imports into California for 50 years, said Tupper Hull, a spokesman for the refiner group Western States Petroleum Association.
However, he added that such a level of production was unlikely to be reached quickly given the difficult geology of the Monterey shale.
(Reporting by Rory Carroll; Editing by Richard Pullin)