Issue Date: September 24, 2007
Underground Gases Don't Always Stay Put
Putting huge volumes of CO2 into the ground begs the question: How long will it stay there? Serious accidents from underground or underwater eruptions of gases have occurred, and these are the kinds of events scientists want to avoid if massive amounts of CO2 end up sequestered underfoot. Here are a handful of illustrations that suggest what energy planners need to think about.
Mammoth Mountain In 2006, three ski patrollers died on the Mammoth Mountain ski area in California from volcanic gases.
Mammoth, a relatively young volcanic mountain, is still outgassing steam and 50—150 tons of carbon dioxide per day from vents on its south flank. Also, the area has experienced significant tree die-off due to high CO2 soil levels.
On April 6, the large volcanic vent on the upper mountain was covered with heavy snow, and the fence around it appeared to be too close to the opening. While four ski patrollers were attempting to reconfigure the fence to keep skiers away from the vent, the snow around it collapsed and two patrollers fell 21 foot into the vent. A third died trying to rescue the first two. All three succumbed from a combination of CO2 and hydrogen sulfide poisoning.
Lake NYOS Nyos is a deep crater lake high on the flank of an inactive volcano in Cameroon. A pocket of magma under the lake continuously leaks CO2 into the water.
In Nyos, a warm layer of water overlies colder, denser water supersaturated with CO2. The lake remains stable most of the time, with the CO2 staying in solution at great depths. But on Aug. 21, 1986, a landslide or a small volcanic eruption on the lake bottom triggered a sudden overturning of the water and an estimated 1.6 million tons of CO2 was suddenly released. It rushed down two valleys, killing about 1,800 people and 3,500 livestock.
HUTCHINSON On Jan. 17–18, 2001, natural gas migrated seven miles from an underground storage site and came up in Hutchinson, Kan., burning down two businesses, damaging 26 others, and killing two people. Nine months of detective work by geologists at Kansas State University was needed to understand what happened.
For many years, an underground natural gas storage field eight miles northwest of Hutchinson had been one of 30 hubs in the U.S. gas distribution system. The gas was contained in man-made salt caverns called jugs, as it is at 26 other U.S. locations.
It turned out that 143 million cu ft of gas from the storage field escaped from a leak in the casing above one of the jugs and traveled through a layer of brittle and possibly fractured dolomite until it reached Hutchinson. On Jan. 17, the gas began to erupt through abandoned brine wells, in some cases causing 30-foot-high geysers. The disaster attracted worldwide attention because many countries use salt caverns to store natural gas.
VERSAILLES, PA. For decades, the air around Versailles, Pa., has had very high methane concentrations.
In 1919, town residents found that they were sitting on a natural gas supply. Instead of digging a dozen wells, which would have been adequate to drain the reserve, one well was drilled for each family—a total of 660 wells. After about 10 years, the supply of usable gas flowing from the wells effectively stopped.
During World War II, residents pulled out the steel casings lining the wells and sold or donated them to the war effort. Consequently, it was impossible to properly seal the wells.
Every few years, high methane concentrations—up to 90%—are found on private property in Versailles. Families that could not afford $10,000 vents to solve the problem have been evicted and their homes demolished.
Recently, the federal government funded a survey of Versailles??? wells. Richard W. Hammack, research geochemist at the Energy Department???s National Energy Technology Laboratory (NETL), using very sensitive methane monitors, found leaking wells under streets, parking lots, and under or near many houses.
The town is installing vents in the ground to try to keep methane from accumulating in in buildings, while NETL tries to devise a permanent solution.
- Chemical & Engineering News
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