SoCal Gas says its blown-out well released less methane than the state estimates

Southern California Gas Company has made public its calculation of how much methane escaped from its ruptured well near Porter Ranch, and it's less than what state experts have estimated.

In a filing with the Securities and Exchange Commission, the gas company says its calculations show about 4.62 billion cubic feet of gas escaped from the broken well at high pressure during a span of four months.

The California Air Resources Board puts the amount at about 5.4 billion cubic feet –  a difference of 14 percent.

In a statement, SoCal Gas said its calculations "align closely with preliminary estimates made by the California Air Resources Board and estimates made by third-party scientists."

Another way of describing the lost natural gas is by tonnage. SoCal Gas said it lost 84,200 metric tons of gas. The ARB has estimated the leak at 94,500 tons. A report in Science Magazine put the loss at 97,100 metric tons and described it as the nation's largest-ever recorded methane leak.

The number matters because it will help determine what SoCal Gas ultimately pays to offset the damage all that methane did to the atmosphere. Methane is a potent greenhouse gas that traps heat and contributes to climate change.

The state is directing the company to fund methane mitigation programs sufficient to offset the environmental damage from the leak, and SoCal Gas has pledged it would do so. However, the company and the state Air Resources Board disagree over how to calculate the damage the leak caused and therefore how much mitigation is necessary. 

In its statement to shareholders, SoCal Gas said it "will finalize its mitigation plan in the coming months."

Some environmental activists are troubled by the company's estimate of the total amount of gas lost. 

"There is a very strong motivation on their part to reduce this number and value for leakage as much as they possibly can," said Mickey Moritz, a staff attorney from the Center for Biological Diversity. "Can they really say that it's exactly 4.62 (billion cubic feet) or is it that they are looking down the barrel of some very tough and expensive mitigation measures, potential lawsuits, and allowing there to be a little bit of underestimation there?"

SoCal Gas said it calculated its figure on the capacity of its underground gas reservoir minus the amount of gas it withdrew for sale to customers while the leak was active.

In a statement, Air Resources Board spokesman David Cleghern said the agency is not accepting the SoCal Gas figure as authoritative because more research is needed to reach a conclusion that is "much more robust and scientifically defensible."

He said the state estimate is based on a broad range of factors, including data from sensors placed around the perimeter of the gas storage field, as well as "ground monitoring, monitoring from the Statewide Methane Monitoring Network, two satellites, JPL monitoring, Scientific Aviation data, the Mega-Cities Methane Monitoring Network and data from JPL’s U2 aircraft overflights." 

SoCal Gas shared its calculations with the Air Resources Board last week, Cleghern said.

Leak costs now exceed value of gas field

The gas leak has already cost SoCal Gas more than the Aliso Canyon Natural Gas Facility cost to acquire and improve, according to the company's statement to shareholders. The company lists the "net book value" of the field at nearly $600 million, and the company has said the leak has so far cost more than $665 million.

About 70 percent of that has gone to relocating residents, many of whom say the leak caused them symptoms such as headaches, nausea and nosebleeds. About 2,500 households remain  in temporary lodging at the gas company's expense.

The company said that although it had more than $1 billion in insurance policies to cover damages from the gas leak, it couldn't guarantee shareholders that insurance would cover all costs. Any overrun, therefore, could bring down earnings.

The company's use of the gas reservoir has been limited while an extensive program is underway to test all 114 gas wells at the facility and isolate those that cannot be brought up to state operating standards.

The company has issued statements that it expects to reopen the Aliso Canyon gas field for full operation by late summer. In the shareholder filing, it said that if it is unable to resume using the gas storage field for injections and withdrawals of natural gas, its earnings could be reduced.