Aliso Canyon: California’s Bellwether Natural Gas Leak
Public attention is growing over a vast, uncontained natural gas leak at the Southern California Gas Company’s Aliso Canyon storage facility in the Porter Ranch area of Los Angeles. The nearly more than 2-month-old leak has captured global attention and drawn comparisons to the BP oil spill disaster in terms of the scale of its climate impacts. Thousands of local residents near the site have been evacuated from their homes, and calls for improved safety provisions – at this storage site and hundreds more around the country – are multiplying.
What’s underground at Aliso Canyon, and why are people concerned?
Aliso is one of 420 natural gas storage fields across the United States. Companies use the fields to store natural gas in summer, when heating demand and natural gas prices are low. They then sell it in winter when demand and prices are higher. To store it underground, companies pump it at high pressures into depleted oil and gas fields, where there’s lots of empty pore space. Think of it as a balloon you can pump up, with the size of the balloon capped by local geology. Although the balloon doesn’t keep expanding, you can pump more and more gas into it by increasing the pressure.
Aliso Canyon is like a big balloon. It’s one of the five biggest gas storage fields in the United States, with a working capacity of 86 Bcf (billion cubic feet) and a total capacity about twice that large. According to the American Gas Association, the average home in the U.S. uses about 200 cubic feet of natural gas per day. At full capacity, then, the Aliso field holds enough natural gas to fuel 14 million homes for a month.
If the knot on a balloon comes undone, the balloon doesn’t pop or empty right away. It takes time for the gas to shoot out the end. That’s what’s happening at Aliso Canyon. The pressurized gas is jetting out the leaking injection well and will keep doing so until the well is capped or the underground balloon deflates.
What we don’t know
We don’t know how full the storage field was when the leak began in October, although the fields are often full in the fall, in anticipation of higher winter prices. Many details about the reservoirs that make up the depleted field have yet to be released. For instance, how connected are they? Is it one big reservoir or, more likely, a series of separate underground fields?
What we do know
What we do know is that a lot of natural gas is leaking into Los Angeles’ air. Aircraft measurements suggest that about 2.6 million pounds (1.2 million kilograms) of methane are leaking each day — enough to heat about 300 thousand homes daily, as well. At current natural gas prices, the daily loss of product is ~$130,000, or roughly a million dollars a week.
“This single leak equals one quarter of all of California’s methane emissions from human activities”
How much is this in relation to methane releases for the entire state of California? Here, the numbers are really interesting. California’s Environmental Protection Agency estimates that all of the methane released from agriculture, industry, and landfills in the state totals about 10 million pounds/day. The current leak is 2.6 million pounds/day. That means this single leak equals one quarter of all of California’s methane emissions from human activities. It’s bigger than California’s total landfill emissions of methane and bigger than all other industrial activities, including oil and gas extraction.
Concerns for human health
An explosion is very unlikely at Aliso Canyon, especially once the gas blows away from the field and is diluted with normal air. Also, unless concentrations reach very high levels, methane and ethane aren’t particularly toxic either until they keep us from getting enough oxygen. That isn’t likely at Aliso Canyon, either.
The nasty smell that’s driving people from their homes comes from the sulfur-based odorants (mercaptans) put in natural gas. Our noses are extremely sensitive to mercaptans, and the levels found in the air around Aliso Canyon are unlikely to cause long-term health consequences. They are unpleasant, though.
“When you look at Aliso Canyon now, everything looks fine. Natural gas is invisible to the naked eye.”
What’s more concerning is if benzene, hydrogen sulfide, or other trace gases are found in the air. Benzene, for instance, is a carcinogen. Here, everyone needs more information to understand the potential risk. To be safe, and because of the noxious smell from the sulfur-based odorants put in natural gas, hundreds of people have been evacuated from the nearby Porter Ranch neighborhood. They probably won’t be able to return to their homes for months. That’s how long plugging the leak is expected to take. The well pipe ruptured underground, and crews are drilling a relief well 8,500 feet down to shut off the leak. So far they’ve drilled about a thousand feet.
When you look at Aliso Canyon now, everything looks fine. Natural gas is invisible to the naked eye. You can be sure people will be watching closely from now on, though.
The balloon has a lot of gas left in it. Stay tuned.
