by Christina Nagy-McKenna, Enerdynamics Instructor
On Oct. 23, 2015, the Aliso Canyon natural gas storage field owned by Southern California Gas Company developed a vast, persistent leak that the utility was unable to contain until Feb. 12, 2016.
Full repercussions of this leak are still unknown. Neighbors from the nearby Porter Ranch community complained of dizziness, coughing, eye and throat irritation, vomiting, nose bleeds, and fatigue. The utility relocated residents in approximately 2,200 households to hotels and other residences for the duration of the leak.
Some residents have already filed lawsuits against the utility, and more are likely to come as the long-term implications of prolonged exposure to methane and gas odorants is unknown and because property values in Porter Ranch will likely decline. Less tangible consequences include the lack of confidence that residents, statewide officials, and lawmakers have in not only the utility but in the California Division of Oil, Gas, and Geothermal Resources. Many of the affected parties are calling for independent safety testing before the Porter Ranch area is deemed safe for residents to return home.
The United States is home to more than 400 natural gas storage fields that form a valuable system to help manage the country’s natural gas storage inventory. Most of the storage fields are depleted oil or gas fields, such as Aliso Canyon. They are valued because they are often located relatively close to consumers and they are plentiful. Pressurized gas is injected into the fields when natural gas demand is lower, and it is withdrawn when consumer demand is higher. By having a storage facility closer to the end-use-customer, it also serves as insurance against problems on the gas pipeline system that may impede delivery of gas to the utility from suppliers who may be located hundreds of miles away.
Most customers are unaware that gas storage systems exist until something goes wrong. In the case of Aliso Canyon, one of the approximately 115 wells in the storage field developed an underground leak hundreds of feet below the earth’s surface. It is believed that a crack formed in the pipe and that gas is escaping either at the end of the concrete casing around the pipe or that there is a leak in the casing as well. The natural gas that escaped the well was no longer under pressure and rose through the ground in the most expedient way possible given the geological constraints of the area.
Leaks at a storage field can occur at any location where there are connection points between pieces of equipment. Thus, seals, flanges, and fittings are all vulnerable points, just as with any other piece of mechanical equipment. Changes in pressure and temperature can also cause stress to a pipe and its fittings, and repeated stress can cause them to ultimately fail. Lastly, connections that are even slightly faulty may take time to develop into larger problems, and normal wear and tear of equipment can lead to failure if not maintained correctly.
So, what can be done to prevent leaks from occurring at the hundreds of gas storage fields around the country? This issue will be widely debated in the coming year just as pipeline safety has been debated since the 2010 San Bruno natural gas explosion.
At a minimum, routine inspections and maintenance must be completed on a regular basis. However, equipment also needs to be inspected if extraordinary events like extreme weather changes and pressure changes occur. Safety valves, such as one removed at Aliso Canyon in 1979, are not required by law, but that may soon change. The U.S. Pipeline and Hazardous Materials Safety Administration issued an advisory bulletin on Feb. 2, 2016, to all natural gas storage facility operators. The agency directed operators to try identify where potential leaks may occur due to chemical or mechanical damage, corrosion, or other substantial issues pertaining to storage-related equipment and parts. The difficulty that storage operators face that pipeline operators do not is that pipes and casings are hundreds of feet below ground and are simply not easy to access.
Ultimately, the Aliso Canyon leak was capped temporarily by drilling an additional well that intercepted the leaking one and then filling it with cement. The lack of a safety value on the well will be debated as well. The leaky well will be cemented closed, but its legacy is likely to shadow the affected customers, Southern California Gas Company, and the gas storage industry for several years to come.
Footnotes and references:
Almasy, Steve, “SoCalGas Stops Leaking Natural Gas Well Near Porter Ranch,”CNN, February 12, 2016.
Atler, Charlotte, “The Worst Gas Leak in California’s History Isn’t Close to Being Fixed Yet, Time, December 15, 2015.
Penn, Ivan, “Gas Leak Will Cost SoCal Gas Billions, Experts Say,” L.A. Times, January 9, 2016.
Snow, Nick, “PHMSA Issues Advisory Bulletin on Underground Gas Storage Facilities,” Oil & Gas Journal, February 3, 2016.
Torres, Zahira and Frank Shyong, “Leaking Gas Well in Porter Ranch Area Lacked a Working Safety Valve,” L.A. Times, January 3, 2016.
Vercammen, Paul, “Methane Gas Leak Forces S. California Residents Out of Their Homes,” CNN, December 31, 2015.
Zhang, Sarah, “California has a Huge Gas Leak and Crews Can’t Stop It Yet,” Wired, December 15, 2016.
“Aliso Canyone Updates,” Southern California Gas Co. website, https://www.alisoupdates.com/main
“Aliso Canyon Update,” South Coast Air Quality Management District website, http://www.aqmd.gov/home/regulations/compliance/aliso-canyon-update
“Oil and Natural Gas Sector Leaks, Report for Oil and Natural Gas Sector Leaks Review Panel,” U.S. Environmental Protection Agency Office of Air Quality Planning and Standards, April 2014.