The fact that hydraulic fracturing requires high volumes of water is well-known. It will, therefore, come as a surprise to many that the massive shift to natural gas from coal caused by the shale boom, means that the actual amount of water used in energy and power generation in the U.S. has significantly dropped.
A new study prepared by the U.S. Geological Survey looked at the amounts of water used in oil and gas exploration. The research found that water volumes for hydraulic fracturing averaged within watersheds across the United States range from as little as 2,600 gallons to as much as 9.7 million gallons per well, with the drillers in the Eagle Ford being the biggest offenders when it comes to water usage.
What’s more, the study found that the unconventional gas and oil wells – which require horizontal drilling to produce – use far more water than their ‘conventional’ counterparts. In fact, in 52 out of the 57 watersheds with the highest average water use for hydraulic fracturing, over 90 percent of the wells were horizontally drilled.
However, those concerned about the huge water usage in oil and gas production and power generation can take comfort in the news that the shale revolution and the resulting widespread shift to natural gas (from coal) in power generation led to a dramatic decrease in water-usage needed to cool the nation’s power plants.
Water we spend on fracking…
From 2000 to 2014, median annual water volume estimates for hydraulic fracturing in horizontal wells had increased from about 177,000 gallons per oil and gas well to more than 4 million gallons per oil well and 5.1 million gallons per gas well. Meanwhile, median water use in vertical and directional wells remained below 671,000 gallons per well. For comparison, an Olympic-sized swimming pool holds about 660,000 gallons.
“One of the most important things we found was that the amount of water used per well varies quite a bit, even within a single oil and gas basin,” said USGS scientist Tanya Gallegos, the study’s lead author. “This is important for land and resource managers, because a better understanding of the volumes of water injected for hydraulic fracturing could be a key to understanding the potential for some environmental impacts.”
The watersheds where the most water was used to hydraulically fracture wells on average coincided with parts of the following shale formations:
- Eagle Ford (within watersheds located mainly in Texas),
- Haynesville-Bossier (within watersheds located mainly in Texas & Louisiana),
- Barnett (within watersheds located mainly in Texas),
- Fayetteville (within watersheds located in Arkansas),
- Woodford (within watersheds located mainly in Oklahoma),
- Tuscaloosa (within watersheds located in Louisiana & Mississippi),
- Marcellus & Utica (within watersheds located in parts of Ohio, Pennsylvania, West Virginia and within watersheds extending into southern New York)
The differences in water-usage in the plays can be partially explained by the fact that shale gas reservoirs are often hydraulically fractured using slick water, a fluid type that requires a lot of water, while tight oil formations like the Bakken (in parts of Montana and North Dakota) often use gel-based hydraulic fracturing treatment fluids, which generally contain lower amounts of water.
…we save on cooling power plants
This, however, is not the full picture when it comes to water-usage and shale production. An indirect – and therefore often overlooked – result of the shale boom is the widespread adoption of gas-powered plants. And a little-known fact is that gas-powered plants need far less water to cool them than their coal-powered equivalents.
As Climate Central points out, the shift to natural gas has translated into big changes in the amount of water being withdrawn from lakes and rivers to cool power plants. And it’s an important shift as nationally, 38 per cent of all water withdrawn is for power plants.
As a result, during the most recent 7-year period with reliable data, water use fell dramatically to 33 trillion gallons in 2012 from 52 trillion gallons in 2005. What’s more, water withdrawals for power generation dropped by more than 1.5 trillion gallons per year in Ohio, New York, and Illinois; 10 states had decreases of 1 trillion gallons or more. Electricity generated from natural gas increased 370 per cent on average in those 10 states, with the largest absolute increases coming in Alabama and New York.
Fact is, that despite fracking being perceived as putting an exceptionally high level of stress on local water resources, in terms of quantity, fracking consumes a relatively insignificant volume of water compared to that required to cool power plants. For the 10 states that fracked the most shale gas wells in 2012, average water consumption for cooling power plants per cubic foot of natural gas burned was 30 times greater than the water consumed for fracking per cubic foot of shale gas.
Sources: Climate Central, U.S. Geological Survey
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