The Southern California well that has gushed climate-changing methane into the sky for three months was operated in a way that is legal but risky, some well experts say.
Southern California Gas Co., a unit of San Diego-based Sempra Energy, injected and withdrew gas through the entire diameter of the well, rather than only through the narrower tubing that runs down the middle of it, Jason Marshall, chief deputy director of the agency that oversees the state oil and gas agency, confirmed. It was doing so when the well failure was discovered.
“It was on injection through both casing and tubing at the time,” Marshall said. “It’s a practice that has been occurring. It’s a practice that we need to look at seriously.”
Aliso Canyon Failed Well Facts
Most recent leak rate measured: 21,500 kilograms per hour of methane
CO2 equivalent climate impact of this rate: About 3.3 million cars on the road
Rough estimate of total loss so far: 4.6 billion cubic feet of gas
Estimate date to stanch methane flow: Late February
Families displaced: At least 2,800
Injecting through both casing and tubing means there was frequently pressure — about 2,600 pounds of pressure per square inch — on not only the 2⅞-inch tubing, but the 7-inch well casing, or wall.
When both tubing and casing of a well are pressurized and flowing gas, it means the space between them cannot be filled with a protective brine. That fluid does at least two things: It inhibits corrosion and can be used to help stifle a well that goes out of control.
“The safest thing to do is inject and withdraw only through the tubing,” said Paul Bommer, senior lecturer at the University of Texas Petroleum Engineering Department who teaches well drilling and production.
“That is the safety margin that is lost in doing it this other way.“
The damage around well SS-25, which was used both to store gas underground and to pump it back up, was discovered by a company employee on Oct. 23.
An inewsource review of state records shows SS-25 was injected every day in October — for 24 days.
In addition, long stretches of the well’s casing are not cemented. Cement protects a well, separates it from any aquifers and binds it to surrounding rock.
"There is nothing protecting either the inside or the outside of the casing in this well," said Anneliese Anderle, who worked in the oil and gas industry and as a state engineer for 40 years. She is now on retainer for a law firm representing residents of Porter Ranch, the Los Angeles County community nearest the well.
More than 20 personal injury and property damage lawsuits have been filed against Southern California Gas and state agencies that regulate it.
“Normally all gas wells would have all their production coming through tubing. The casing is then added protection,” Anderle said.
The Aliso Canyon Natural Gas Storage Field provides the gas that is burned in 14 Southern California power plants. Natural gas is also used for restaurant cooking, refineries, and as basic material for making pharmaceuticals, chemicals and fertilizers.
As the gas disaster began, Aliso Canyon was approaching maximum storage. The country was setting records for gas stored underground in early November, said Chris McGill, a geologist with the American Gas Association. The amount of gas that went to power generation was also a record. “So we had record after record after record, supply and demand,” McGill said.
Southern California Gas declined to make someone available to discuss production and injection practices at the underground field. But in the past, Gillian Wright, vice president for customer services, and other officials have said they will not discuss anything related to potential causes of the well failure until the leak is stopped and the pipe and the casing are removed and examined. Wright said the company is very concerned about the impact of the release and “the impact of carbon dioxide and greenhouse gases on the environment.”
But bringing gas up through both pipes, sometimes known as strings, at the same time, made sense to David Schechter, a professor at Texas A&M University and an expert in gas injection and other fluid injection into wells. The tubing, he said, may not provide a company enough diameter.
“You may have to produce through the tubing and the casing in order to meet the demand of a customer,” he said.
But he acknowledged this would have a downside.
“Absolutely,” he said. “It's known if you get to very high rates of gas production, you reach what's called an erosional rate. That starts to erode or pit the casing.”
Aliso Canyon Natural Gas Storage Field is a natural sandstone formation originally drilled for its oil-bearing rock. When the rock pore spaces were pumped clean, the reservoir made an attractive vessel for receiving piped-in gas. Southern California Gas could buy it inexpensively in the off-season, and store it in anticipation of winter or favorable market conditions. Then wells would pump it out.
The company converted SS-25, one of more than 100 in the field, from oil extraction to gas storage in 1973. Aliso Canyon is the company’s largest storage field.
The fact that gas was being brought up and forced down both the annulus and the tubing of a partially uncemented 63-year-old well many days of the year does not necessarily explain how a hole was blown or eaten through its 7-inch casing. The hole is located near where a layer of outer casing ends, about 990 feet deep in the ground. That area, where outer casing stops, known as the shoe, is a point where wells can fail, Anderle said.
But the conditions combine with other facts to paint a picture of a well in potential jeopardy.
• The safety valve that had once allowed operators to shut off the well in the event of an accident like this one was removed in the 1970s, a fact first reported by L.A. Weekly.
• Southern California Gas was having increasing safety issues and leaks at its storage field, it stated in a filing for a rate increase with the California Public Utilities Commission, a fact first reported by the Los Angeles Daily News.
State records show gas was forced down SS-25 on 197 of the 237 days prior to the disaster. In only two other years had the well been injected so often, as measured by injection days, going back to 1978.
The records from the California Division of Oil, Gas and Geothermal Resources also show the well was injected 24 days in October. It’s not clear how that squares with Southern California Gas statements that its employee discovered the blowout on Oct. 23 and halted injection then.
McGill declined to say whether pressurizing both the tubing and the casing in gas storage reservoirs is a standard practice. Several other natural gas experts declined also.
But he said the nation’s natural gas use is increasing and massive storage fields like Aliso Canyon are important.
“The variability of consumption is extraordinary from a summer month to a winter month,” he said. “You can’t construct a permanent flowing gas system just to meet that peak.” Storage becomes the critical balancer.
But the canyon is receiving no more gas now. The state has halted it. Urgency legislation authored by state Sen. Fran Pavley sits on the governor’s desk. It would allow no further injection until the field can be proven safe, a new burden of proof for this little-known link in the gas supply chain.
