On October 23, 2015 methane began leaking from an underground storage facility in the Aliso Canyon Gas Storage Field near Los Angeles California. Today gas continues to spew out of the ground. The storage facility estimates it will still take until late February at earliest to stop the leak. In the meantime more than 2,000 residents will remain evacuated from the area for health reasons related to high exposure. Methane can bind to blood in the place of oxygen; symptoms can include headaches, nausea, vomiting, dizziness, weakness, and loss of coordination. In particular residents of the Porter Ranch community near the leak suffer increased incidents of headaches and bloody noses. Additionally, methane in high enough concentrations (4.4 to 17%) is highly explosive.
The methane leak has repercussions beyond creating health problems and for local residents. Currently 88 600 tonnes have been released at rates of up to 50 000 kg per hour. While the rate of release has been decreasing since they peaked on November 28, 2015, this continues to represent a significant emission. This is a big issue for not just California, but the world, as methane is a powerful contributor to the greenhouse effect. Generally energy from the sun which enters the earth’s atmosphere is UV (400 to 10 nm), visible (400 to 700 nm) or near Infrared (0.75 to1.4 μm) and is able to travel easily through the molecules in the atmosphere. However, energy radiated from the earth is long wavelength infrared (4-100 μm) which is easily captured by molecules like carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). Green house gases then radiate heat, increasing the thermal energy being radiated to Earth’s surface. Methane absorbs strongly within the wavelength region of 3.5 to 8 μm. Relative to one kilogram of carbon dioxide, one kilogram of methane has about 25 times more impact on climate change over a 100-year period. Once in the atmosphere methane takes approximately 12 years to break down.
Carbon dioxide and methane are the two largest greenhouse gases emitted by human activities in the United States according to the United States Environmental Protection Agency. Methane can also be naturally occurring and is given off by wetlands, landfills, and agricultural activities (manure management accounted for 10% of 2013 US methane emissions). The Aliso Canyon leak has been reported to represent approximately one fourth of the methane emissions from California. In a press release the company claimed that the estimated cumulative emissions from the leak represent approximately 1% of total emissions. Southern California Gas Co., the owners of the storage facility, had created a plan to capture and burn off escaping gas. however it was abandoned due to concerns of possible explosions. Burning the gas would have both halved emissions and relieved symptoms of methane exposure being experienced by the community.
More importantly, this disaster highlights lapses in oversight and design for methane storage and an increasing possibility that aged infrastructure may lead to further issues. The source of the leak has been identified as a well 914 m below ground. Repairing the leak requires crews to drill a new well deeper than the leaking well, then redirecting flow. Redirecting flow will require locating a 7 inch pipe located just under 500 m below the surface and situated among other pipes. This will require magnetic-ranging techniques. High levels of methane represent a constant explosion hazard.
The Aliso Canyon facility was originally built for the oil industry approximately 60 years ago and was repurposed for natural gas storage after the oil fields went dry. Failing underground infrastructure not only increases the chances of leaks to the surface but could also endanger underground aquifers according to R Rex Parris, the lawyer representing residents affected by this current leak. They also pointed out that the continued injections of gas into the reservoir in the time after the leak occurred should have stopped much sooner. Serious problems have occurred in other facilities leading to lawsuits in Kansas, Texas, California, and Colorado for leaks which caused explosions and groundwater contamination.
Experts have been warning about the hazards of oilfields repurposed for methane storage for some time. In the book Gas Migration: The events preceding Earthquakes (2000), the authors warn that gas in abandoned oil fields can be over-pressured by repeated gas injections causing vertical fractures in rock, making surface leaks more likely. The breakdown of cement seals on active and abandoned wells also contributes to gas leaks. Brent Miyazaki, author of Underground Gas Storage (2009), agrees that gas injection causes pressure fluctuations which lead to a high probability of leaks and containment failures occurring at underground facilities. Furthermore, let’s not forget that the San Andreas Fault runs only 56 kilometres north-east of Los Angeles.
Criticism has also been directed at authorities for failing to maintain staff with adequate technical backgrounds to evaluate hazards and the city for allowing residential housing to be developed so close to the oilfield. Experts now call for a variety of measures to increase monitoring and routine gas migration studies. This is a challenging problem as the methane storage allows for reasonably priced fuel for 21 million people.
An overall lack of monitoring as facilities age is a problem also experienced in Canada. Three Waterloo professors addressed this issue from a Canadian perspective in their May 2014 report, Towards a Road for Mitigating the Rates and Occurrences of Long-Term Wellbore Leakage. In addition to the repercussions of potential leaks, they also address the economic impacts of remedial workovers on the industry.
Ultimately, this recent methane leak in California has served as a wakeup call to regulators and industry alike. Although this leak has made headlines due to its enormous effect on residents in the Porter Ranch area, there are many lessons to be learned for similar setups worldwide. Particularly in places where there aren’t dense populations to quickly notice when things go amiss.
As engineers we design for a certain lifecycle assuming it will be followed and retrofits of designs can be a risky business. Personally this issue has reminded me of the importance of remembering to constantly validate that aged infrastructure is behaving as expected and to design in adequate redundancies so problems can be remedied more effectively than seen here. Monitoring of a system does not end when the lifecycle has finished, in fact often it should be intensified. For every decision there are repercussions and consequences which we must always keep in mind.
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