According to an article published today in the Wall Street Journal:
"California's Monterey Shale formation is estimated to hold as much as two-thirds of the recoverable onshore shale-oil reserves in the U.S.'s lower 48 states, but there's a catch: It is proving very hard to get.
Formed by upheaval of the earth, the Monterey holds an estimated 15.4 billion barrels of recoverable shale oil, or as much as five times the amount in North Dakota's booming Bakken Field, according to 2011 estimates by the Department of Energy. The problem is, the same forces that helped stockpile the oil have tucked it into layers of rock seemingly as impenetrable as another limiting factor: California's famously rigid regulatory climate.
California has become one of the U.S.'s top oil-producing states over the past century, largely by tapping into the easier-to-get oil that has seeped out of the Monterey beneath places like Bakersfield and Los Angeles County. But with production in general decline since the 1980s, producers are trying a smorgasbord of techniques—called enhanced oil recovery in industry parlance—in an effort to tap into the mother lode.
So far, there have been no production breakthroughs".
Besides there is a strong oppossition by the enviromentalists,because of their concern of its impact of e.g. fracking which lowers the quality of water.
Other technologies are also strongly opposed by critics and environmetalists.
