Having worked in Exploration and in Production across California, I can tell you it is well-endowed with large legacy fields, including 4 of the ten largest conventional oil fields in the lower 48 in Belridge, Midway-Sunset, Kern River and Wilmington.
It also possesses one of the greatest accumulations of unconventional oil potential in the Monterey Formation. Its offshore potential is also of staggering size and relatively low risk geologically.
It is sad that the state discourages the realization of the potential of these horizons as fraccing is minimized and is in the process of being legislated out of existence, and there has been a ban on new offshore platforms after the spill off Santa Barbara almost 50 years ago.
California has also systematically destroyed the coal industry as it has closed 11 coal-power plants in the past 10 years, with a single coal power plant remaining. And forget about any new nuclear power plants there, ever.
No, California is ostensibly hitching its chain to the doubtful renewable energy sector. I say ostensibly as it still relies greatly on being provided power by nearby states.
We in other states must take heed on what has happened in California.