During the first two weeks that Southern California Gas Co. (SoCalGas) began reinjection operations at its troubled Aliso Canyon natural gas storage facility, the company discovered a gradual pressure buildup at 13 of the 39 injection wells that had been brought back online.

Correspondence between SoCalGas and the state Division of Oil, Gas and Geothermal Resources (DOGGR) shows that two of the 13 wells were returned to operation following “corrective action” by the company, with a third well expected to be reactivated soon. Of the remaining 10 wells, six have been taken out of service, plugged and filled with water, while the remaining four have been taken out of service and stabilized.

“We have taken a measured, prudent approach and in each case, when the pressure build-up was detected, we took the wells out of service and maintained them in a safe state,” Rodger Schwecke, SoCalGas’ vice president for transmission and storage, wrote in an Aug. 28 letter to officials with DOGGR and the California Public Utilities Commission (CPUC). “We have been following our well pressure monitoring policies and procedures on all the observed wells, even though the pressure limit specified within these procedures was only reached on two wells…

“Throughout this process, we have followed, and continue to follow, our applicable protocols and policies, including agency notification, and we are communicating and sharing information regularly with DOGGR and the CPUC. There have been no releases of gas associated with the pressure anomalies, and even the highest monitored pressures have been a fraction of the rated capability of the casing.”

In a return letter dated Sept. 1, Kenneth Harris, the state oil and gas supervisor at DOGGR, told Schwecke state law mandated that each of the wells remain shut in until they are “repaired and tested to DOGGR’s satisfaction. After testing, each well will continue to be closely monitored while on injection.”

DOGGR spokeswoman Teresa Schilling told NGI on Tuesday that the agency has inspectors on site and that the company is being cooperative. “They understand that it’s in their best interest to operate as safely as possible. We’re down there to ensure that they do that.”

On Monday, DOGGR said the highest pressure elevation recorded at the 13 wells was 700 pounds per square inch (psi). The agency called the reading “an early indicator that is well below pressures that would indicate a need for concern.

“Each of these wells’ outer casing — the part of the wells which contain the areas exposed to this 700 psi pressure — had previously passed testing to withstand more than 3,500 psi,” DOGGR said. “The pressures indicate that adjustments need to be made to the ‘packers’ of these [wells],” which would be performed using a workover rig.

“There is no indication of a lack of mechanical integrity for any well. The packers are completely within the outer casing of the well, and their function can be adjusted without releasing any natural gas into the atmosphere. Until the packers are adjusted, the wells are not allowed to return to service.”

Citizens for Responsible Oil and Gas (CFROG), an environmental group, said it supported the shut in of the wells.

“The shut in of these wells is a good step in the right direction for a public utility,” CFROG Executive Director Kimberly Rivers told NGI. “With ongoing reports of area residents suffering from health impacts and still no reported cause of the initial leak it makes sense for SoCalGas to shut in wells that pose a risk.

“The initial leak and the ongoing issues at this site provide more evidence of the true risks and impacts of continuing to operate aging oil and gas infrastructure without the health impacts and public safety risks being fully assessed and reported.”

DOGGR suspended natural gas injections at the 100 Bcf facility after a major leak was discovered in October 2015. The leak was permanently sealed four months later. The regulatory agency also ordered a comprehensive safety review in which each of the 114 wells at Aliso Canyon either had to pass a battery of tests to potentially be eligible to resume gas injection or be taken out of operation and isolated from the reservoir. The root cause of the leak has still not been determined.