Aliso Canyon gas leak
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Aliso Canyon leak site on December 14, 2015
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| Duration | October 23, 2015 – February 18, 2016 |
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| Location | Aliso Canyon Oil Field, Porter Ranch, Los Angeles, California |
| Coordinates | 34°18′54″N 118°33′51″W / 34.31500°N 118.56417°WCoordinates: 34°18′54″N 118°33′51″W / 34.31500°N 118.56417°W |
| Also known as | Porter Ranch gas leak / blowout |
| Type | Gas leak Blowout (well drilling) |
The Aliso Canyon gas leak (also called Porter Ranch gas leak and Porter Ranch gas blowout) was a massive natural gas leak that was discovered by SoCalGas employees on October 23, 2015. Gas was escaping from a well within the Aliso Canyon's underground storage facility in the Santa Susana Mountains near Porter Ranch, Los Angeles. This second-largest gas storage facility of its kind in the United States belongs to the Southern California Gas Company, a subsidiary of Sempra Energy. On January 6, 2016, Governor Jerry Brown issued a state of emergency. The Aliso gas leak's carbon footprint is said to be larger than the Deepwater Horizon leak in the Gulf of Mexico. On February 11, 2016, the gas company reported that it had the leak under control. On February 18, 2016, state officials announced that the leak was permanently plugged.
An estimated 97,100 tonnes (95,600 long tons; 107,000 short tons) (0.000097 Gt) of methane and 7,300 tonnes (7,200 long tons; 8,000 short tons) of ethane were released into the atmosphere, The initial effect of the release was to increased the estimated 5.3 Gt of methane in the Earth's atmosphere by about 0.002%, diminishing to half that in 6-8 years.
It was widely reported to have been the worst single natural gas leak in U.S. history in terms of its environmental impact. By comparison, the entire rest of the South Coast Air Basin combined emits approximately 413,000 tonnes of methane and 23,000 tonnes of ethane annually.
After oil was discovered at Aliso Canyon in 1938, J. Paul Getty's Tidewater Associated Oil Company produced oil and gas until the Sesnon-Frew reservoir, the largest reservoir within the oil field, was depleted in the early 1970s. On December 18, 1968, a blowout and fire, destroying equipment but causing no injuries, occurred at one of the wells when an operator attempted to remove two gas-lift valves. Getty sold his portion of the field to Pacific Lighting Company, a gas company, which repurposed it to gas storage in 1972. As opposed to current practice, older wells were not sealed to the surrounding rock formation, including their often more than one mile of steel casing. Today, "cement from the surface of the ground to the bottom of the well [...] makes the casings stronger and protects them from water." The Aliso Canyon natural gas storage facility contains 115 wells tapping a reservoir that "hold[s] up to 86 billion cubic feet of natural gas for distribution to residences, businesses, and electric utilities in the L.A. basin". The field is the second largest storage facility of its kind in the United States.
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