"You're squeezing oil from a rock," he added. "For most oil fields, you only recover about 30 to 40 percent of what's there. So, 60 to 70 percent of the oil is still in the ground."
That means more drilling, and in some neighborhoods, more noise, more trucks and dust, and more unhappy neighbors.
"It is a constant battle of noise, gas releases, vibrations," said Gary Gless of Windsor Hills, Los Angeles. "It has been for a lot of people, even property damage where the houses have been shaking, cracking, when the drilling has been going on."
Gless says the oil being drilled in Los Angeles won't solve the nation's supply problem.
"Basically, it would be a drop in the bucket for what we really need," he said. "And what they want to do is basically drill 24/7 for the next 20 years."
It is questionable whether urban oil can do anything to alleviate the problem of supply and price in the coming years. The entire U.S. produces just short of 1.9 billion barrels.
"If you look at the total number of small wells in the United States, they produce 20 percent of our domestic crude supply," said John Felmy, chief economist at the American Petroleum Institute. "These are very small wells, producing a couple of barrels a day, so you would have to have a very large number of them for a significant increase in production."
But in Wilmington, they have already increased production from 369 barrels a day to 3,200, and as they continue to drill, they hope to get up to 5,000 or 6,000 barrels of oil a day out of these partially-depleted fields.
"We're still going to rely tremendously on imported oil," Dahlgren said. "Every bit helps. It's one less ship off the coast bringing oil from someplace else."