One of the biggest controversies surrounding shale gas as an energy source is whether or not chemicals seep into the water table. A test has been developed by researchers at the University of Edinburgh to check for contamination. This could help monitor the safety of shale gas and coal bed methane extraction. Benjamin Plackett explains how the test works.
Shale gas extraction—also known as fracking—may offer new economic opportunities, but it remains a contentious way to get natural gas out of the Earth. Perhaps the greatest of concerns for local communities is the risk of chemicals getting into their water supply.
Researchers at the University of Edinburgh have developed a new test to monitor the safety of shale gas extraction by checking for groundwater contamination.
Fracking involves drilling holes in the ground—down which a pressurized mixture of water, sand and chemicals is pumped. This mix is forced into the rock formation, which in turn displaces the shale gas out through a well.
Technically speaking, water contamination during fracking shouldn’t actually happen, explained Stuart Gilfillan, one of the geoscientists behind the test.
The incidents in the United States where methane has leaked into the water table was because the drilling holes were poorly sealed—it was sub par standards that caused the contamination, rather than anything integral to the extraction process itself, he argued.
“However, the greater number of wells required for developing shales mean that accidents or oversights are more likely to happen,” he added. It’s because of this risk that monitoring any potential seeping of chemicals into the ground water has become important.
Gilfillian and his colleagues developed a new test to both monitor any contamination and track the origin of its leak. The technique is called a fingerprint analysis and it measures levels of inactive elements called noble gases, which are found in shale gases.
The concentration of nobel gases present in an underground reservoir of methane varies with the location and depth at which it’s found. So by measuring these concentrations, Gilfillian is able to create a unique profile for each reservoir of natural gas, which he calls a “fingerprint.”
If a source of shale gas was to be extracted, Gilfillian would first produce a fingerprint of it, he said, “which can then be used as conservative tracers to track that gas as it migrates, mixes and interacts in the subsurface.”
In other words, once the fingerprint has been taken, authorities could monitor the ground water regularly to screen for the fingerprint. If they found the fingerprint in the groundwater, that would indicate a contamination.
But more than just knowing that the water supply had been compromised, Gilfillian’s test also pinpoints which gas well is responsible for the leak since each fingerprint is unique.
“Knowing the source of a gas is extremely important for understanding the problem, mitigating any effects, and considering any subsequent litigation,” explained Gilfillian.
Whether or not such a test will quell the anxieties of local residents and therefore expand fracking operations remains to be seen. Gilfillian is still in the development stages of his research and is yet to figure out how much it would cost to roll out his test at scale. But considering the level of investment required to extract, store and transport shale gas, it seems to be a marginal addition to the cost of the process.
Original Article: https://www.eniday.com/en/technology_en/test-for-safety-of-shale-gas/
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