This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Propane Fracking vs. Water Fracking: Which is better (worse)?
With all the negative attention surrounding hydraulic fracturing, a process that stimulates shale plays but requires the use of millions of gallons of water, it is no surprise that companies are looking at alternatives. One such alternative that has recently emerged uses gelled propane instead of water. According to GasFrac Services, a relatively new Canadian oilfield service company, this type of “[propane] fracturing can deliver economic and environmental benefits.”
But are there really environmental benefits, and is gelled propane safer than using water? As an engineer with some history in the oil and gas industry, I hope I can shed some light on this “proprietary innovation”.
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Today, oil and gas companies use water for hydraulic fracturing because it is cheap, abundant (relatively) and safe (doesn’t explode). A typical frac job will require the use of about four million gallons of water, most of which will stay down hole, in the reservoir, permanently. The small percentage that flows back out of the well - called flowback water – must be treated and disposed of.
If these companies chose to use gelled propane, then these wells would use less water and produce less wastewater. This is a universally positive change, and particularly good in areas like west and south Texas where water supply is limited. Additionally, fracking with water can sometimes cause formation damage, or damage to the reservoir, which can close flow pathways and prevent oil and gas from being produced. Using gelled propane would likely reduce formation damage during the fracking processes, which means better overall recovery, and a more profitable well.
However, while the site specific water consumption could be greatly reduced, the impacts to the total lifecycle water consumption throughout the entire production pathway are not clear. There is a significant amount of water that goes in to producing and liquefying propane, so while you might not use much water at the well site, the total amount of water consumed could still be high.
Using liquid propane could also pose a safety risk. Propane, under normal conditions, is a gas. Liquid propane is a liquid because it is held under pressure. If there is a leak above ground, the propane could form a vapor cloud and explode, if there were any ignition sources nearby (a running vehicle, perhaps). This risk already exists because the natural gas that you are producing is a gas, as the name suggests, so the incremental risk may not be significant. GasFrac Services claims that they have multiple safety barriers, and insists the process is safe. However, regardless of their barriers, propane is still significantly more explosive than water so there is some added risk.
GasFrac mentions that the liquid propane is “gelled with proprietary chemicals”. In other words, we don’t know what they are putting in the propane. But, it is likely similar to the chemicals used in conventional fracturing. For those concerned with groundwater contamination by fracking chemicals, using propane does not eliminate the risk for water contamination, since you are still using chemicals. (By the way, just because it is a ‘chemical’ does not mean it is evil. Did you know that water is a chemical? So is oxygen. How about these scary sounding chemicals: phosphoric acid and potassium benzoate? These are ingredients in diet coke.)
One reason propane has not yet been used widely is because it is more expensive than water, and the benefits may not justify the costs. However, the GasFrac process is fairly new, and they have demonstrated some promising metrics, such as longer fracture lengths and higher production rates compared to water fracking, which means it might be more effective. If it is truly more effective, its use may become more common. But, if there are any significant safety incidents, the industry will avoid it, and stick with the tried and true water method.
The bottom line is this: There may be some benefits to gelled propane, one of the biggest being a decrease in on-site water consumption. If it is truly better, the industry will recognize that and we could see a shift away from such water intensive fracking methods. But perhaps what is more likely is that propane fracking be used in places where there are extreme water shortages. Otherwise, water fracking will likely continue to dominate.
About the Author:
Scott McNally is an energy engineer who has spent the past year working on national energy policy issues in Washington, DC. He has worked as an ORISE Fellow with the Department of Energy's ARPA-E Program and an energy and climate researcher with the White House Council on Environmental Quality. Previously, Scott was a project engineer for Shell Oil Company and an environmental engineer for Valero. Scott has a B.S. in Chemical Engineering from the University of Texas at Austin, and is currently completing a Masters in Energy Resources Engineering at Stanford University. Scott was invited to be a guest blogger by Plugged In’s Melissa C. Lott. You can reach Scott via e-mail at scottmcnally at gmail dot com.
Photo Credit: Photo by Cliff Weathers and used under this creative commons license.