A Southern California Gas Company executive told state lawmakers this week that the company continues to use the same controversial method to inject and withdraw natural gas that has been cited as a possible cause for the uncontrolled, four-month gas leak near Porter Ranch.
According to state records, as many as 51 wells in Playa del Rey, Santa Clarita and Goleta employ the method which uses both the inner tubing of a well and the the gap between the tubing and the outer metal casing to move gas in and out of an underground reservoir.
Gas wells are like a straw within a straw. The inner tubing of a well, measuring about 2.5 inches across, is placed within a 7-inch metal casing, often surrounded by concrete. Injecting and withdrawing gas through both the inner tubing and the space between it and the outer casing is a fast way to move a large volume of gas quickly, but it has safety drawbacks.
The method has been barred at all 114 wells SoCal Gas operates at the Aliso Canyon Natural Gas Storage Facility near Porter Ranch.
One of those wells blew out in late October and spewed methane and other chemicals unimpeded for four months until the well was permanently sealed in February. Thousands of families fled Porter Ranch during the course of the leak, complaining of adverse health effects. Many have yet to return.
The cause of the leak still has not been determined, but one theory focuses on the use of both inner tubing and the gap between it and the outer casing to move gas. The practice can erode the casings leading to leaks.
Though currently barred at Aliso Canyon, the practice is still allowed at three other local gas storage reservoirs run by SoCal Gas.
Of those fields, the oldest is in Playa del Rey near a neighborhood of bluff-top homes. Five of 24 wells there are injecting and withdrawing gas through both the inner tubing and the gap around the tubing, said Donald Drysdale, spokesman for the state Department of Conservation.
At two other SoCal Gas facilities the practice is even more common. At the Honor Rancho storage field near Santa Clarita, 33 of 35 gas wells use both the inner tubing and the gap inside the casing. At the La Goleta storage field in Santa Barbara County, 13 of the 17 wells use the practice to inject and withdraw gas.
The practice of injecting and withdrawing is not barred at the other three facilities. It would take new permanent regulations to change that, Drysdale said.
Rodger Schwecke, SoCal Gas vice president for transportation and storage, told a state Senate hearing on Tuesday that the company was moving toward a "tubing flow only scenario" at all wells it operates but had not yet achieved that goal.
"That scenario for SoCal Gas is something that we believe creates that extra safety level that will create more comfort that the wells are operating safely," Schwecke said. "We'll be doing it at Aliso Canyon, we're at almost the same place at Playa del Rey. Our direction is to go to that 'tubing flow only' scenario to create that extra safety layer."
Schwecke made his comments at a hearing called by Sen. Fran Pavley to discuss gas well safety.
In a statement released Wednesday, SoCal Gas said it would only use the inner tubing to move gas through wells at Aliso Canyon once it's allowed to resume operations there. It also said it will work with state and federal regulators on new rules on moving gas through both a well's tubing and casing.
The company has characterized the change in how it moves gas as voluntary for safety reasons, but it may not have much choice in the future. The practice of using both tubing and the gap space to move gas could be prohibited when the state Department of Conservation issues new permanent regulations for gas storage fields.
The well that ruptured in Aliso Canyon, known as SS-25, had been moving gas in and out through the tubing and casing, said Jason Marshall, chief deputy director of the California Department of Conservation. That agency is parent of the state Division of Oil, Gas and Geothermal Resources which oversees SoCal Gas storage fields,
"There are more than a few wells in the field that were doing that," Marshall said, referring to the Aliso Canyon field.
The 9,000-foot deep well that ruptured was missing a layer of cement between the metal casing and the earth for much of its length, Marshall said. If the gas had moved only within the central tubing, a break in the tubing would have been less likely to result in the massive leak. But with gas moving at high pressure in both the central tube and the gap between the tube and the metal casing, the well was far more vulnerable to a leak, he said.
"When you say we're only going to allow production through tubing and not through (the gap between the tubing and) casing, then the exterior of the tubing is your first line of protection, that void space in the casing and the metal of the casing itself is your second line of protection, with cement being your third line, if the cement is there," he said during an interview shortly after the ruptured well was capped.
Right now, by order of the state Public Utilities Commission and Gov. Jerry Brown, the Aliso Canyon gas field has been mostly take off line, maintaining a low level of gas storage and low pressure while its wells are tested for safety. No new gas injections have been allowed.
Marshall said his department is drafting new regulations mandating that any wells in the Aliso Canyon field "will only be allowed to produce or inject through tubing. There will be no more production or inject through casing."
However, the practice is not yet prohibited at California's 13 other gas storage fields.