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The root cause of the largest methane leak in U.S. history that occurred in 2015 at the Aliso Canyon natural gas storage facility in Southern California likely will not be known until late this year, according to the energy consulting firm conducting an independent investigation.
Houston-based Blade Energy Partners, which is working with state officials and Southern California Gas Co. (SoCalGas), has begun the metallurgical phase of its three-part investigation, examining a part of the storage well (SS#25) pipe casing and joint that cracked around its circumference and laterally down its side.
Blade posted its protocol for the metal testing in an internet posting in mid-February. The root cause analysis (RCA) is being completed as investigations continue in parallel by the California Public Utilities Commission (CPUC) and Division of Oil, Gas and Geothermal Resources (DOGGR).
After pulling tubing and casing from the storage well and transporting it to a Houston facility, Blade is analyzing the cracked segment of the 892-foot-long uncemented seven-inch diameter production casing from SS#25, one of 114 storage wells at the 3,600-acre facility at the time of the leak's identification in late October 2015.
SoCalGas, CPUC and DOGGR officials confirmed that gas was injected and withdrawn through the tubing and the space between the tubing and the casing, something that now is forbidden by California's more stringent gas storage rules that were put in place following the incident. Thousands of nearby residents were forced to move out of their homes for several months.
"During the state's comprehensive safety review, every casing in every well approved for use went through an eight-step diagnostic test and had to pass those tests before being approved by DOGGR," a SoCalGas spokesperson told NGI, adding that regulators called the test the most comprehensive in the nation.
"Also, under the state's new regulations, gas no longer flows through the casing. It only flows through a brand new steel inner tubing. The outer casing now only serves as a secondary protection against leaks."
By July Blade expects to complete various permit, logging and data collection work, along with collecting two additional joints from the well hole. Also by July, it expects to complete nondestructive evaluation inspections and metallurgical analyses. The final report by Blade is tentatively Nov. 20.
"This date is dependent on the timely completion of the next steps in the technical data gathering process,” including metallurgical and other work,” said a DOGGR spokesperson. The final parallel report from DOGRR is not expected to be issued after Blade finishes the RCA work. "And even if Blade hits its estimated target for November this year, there is no estimate when the final DOGGR investigative report will be issued.”
In its report to the CPUC last month, Blade indicated a primary focus is metallurgical and fracture, or fractographic, testing. A downhole video camera last August identified the source of the leak at the 887-foot level underground, within five feet of the bottom of the casing.
"The inspection identified a fully parted casing," Blade said. The joint associated with the severed casing was identified as Joint 22. It said 24 casing joints were taken from the well and the top and bottom fracture surfaces on either side of Joint 22 were recovered. "Visual examination of the parted casing showed a 19-inch long axial split on the lower parted casing that had merged with the circumferential fracture."
Blade's report verified that "thinning" of the casing wall and corrosion were evident with the lengthwise split, and the severity of corrosion appeared to intensify with increasing depth.
"On-site examination of the failure indicated that the circumferential parted-failure of Joint 22 was brittle with little plastic deformation such as necking or shear."