At the state Division of Oil and Gas offices in Long Beach, there are maps that tell much about the geological and mineral development of Los Angeles and Orange counties.
In fascinating detail, these maps show the boundaries of every oil field and the location of every oil well ever drilled, from Newhall in the north to Newport Beach in the south.
Rich History in Oil
In some respects, the maps are a reminder of Southern California's rich history as an oil and gas producer since the late 1880s.
Since last week's methane gas explosion that injured 22 people in a Fairfax district discount department store in Los Angeles, they also serve as a startling reminder that some of the Los Angeles Basin's most concentrated residential and business areas have been built on what were once thriving oil and gas fields.
There are 70 oil fields in the basin, 19 of them abandoned.
"There are uncounted numbers of developments, a high degree of urban development . . . in and around and over the old oil fields," said R. K. Baker, operations supervisor for the Division of Oil and Gas.
Indeed, many of the residential areas immediately northwest of the Harbor and Pasadena freeways near downtown Los Angeles are dotted with hundreds of abandoned and even some active oil wells. There are active oil wells in Beverly Hills and throughout the Westside. Many coastal cities in Los Angeles and Orange counties were virtually built on top of oil fields, as were inland cities, including Whittier, Montebello and Newhall.
In Newport Beach, opposite Coast Highway, a flare burns off malodorous fumes of seeping methane gas that linger as a mostly annoying legacy of a low-grade oil field in what is now Balboa Shores.
Big Onshore Producer
Huntington Beach remains one of California's largest onshore oil producers, with hundreds of active wells, hundreds more that are inactive and more than 2,000 abandoned wells.
In Brea Canyon in northern Orange County, oil still seeps from outcroppings of sandstone. That seepage led to the original Brea-Olinda oil field strike more than 70 years ago. Numerous active wells are still in operation.
But now, geologists say, there is growing concern that the old oil fields are beginning to repressure themselves--causing a potentially dangerous situation where there is above-ground development.
The repressurization occurs as water intrudes into the field, squeezing the remaining oil and gas upward. Often, the residual oil and gas can amount to 60% to 70% of the original find.
Don Lande, technical support supervisor for the Division of Oil and Gas, said geologists do not know how long it takes for repressurization to occur. But once it happens, he added, a field has as much pressure as it did before any oil or gas was removed.
"If something is going to leak, it will leak a little faster if the pressure is high," Lande said. "It (a field) may not have leaked 20 years ago, but now it may start to leak."
There are at least 51 active locations in Los Angeles County where oil and gas are seeping naturally to the surface through faults and cracks in the strata. Most of those leaks are in the La Brea-Hancock Park-Fairfax area, where last week's blast occurred. That is one of the areas Lande said may be repressuring.
In Orange County, there are at least 21 such active sites and one location that shows evidence of recent seepage in the bluffs above Newport Beach's flare, or eternal flame as it is sometimes called, according to the Division of Oil and Gas survey.
Sixteen are clustered in the Brea-Olinda area on mostly undeveloped oil company land, leaking oil at rates ranging from 10 gallons to more than 500 gallons annually.
Five active oil and gas vents in Newport Beach are clustered mainly in the vicinity of Balboa Boulevard and 43rd Street and the west harbor area. In a cove east of Channel Park, bubbles of the sulfurous stuff can often be seen.
None Pose a Hazard
But according to Lande, none of the leaks in Orange County pose a hazard.
"I don't think there's any danger of the Fairfax incident being repeated anywhere in Orange County," Lande said. "There are no serious leaks in Orange County, just a few little nuisances here and there."
"There are oil fields, some abandoned and some not. And these oil fields will leak gas and/or oil from time to time in future years . . . . But we don't have the large gas seepage like that Fairfax area."
No seepage has been noted near active or abandoned wells in Huntington Beach. Lande said that may well be because of the volume of oil production in the city's active fields.
"I believe if you're producing in an oil field, the chances of seepage are less because you're siphoning off the pressure that produces the seepage," Lande said. "If . . . pressures are low, the chances for seepage are diminished."