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It’s strange, in a way, to talk about water scarcity, because water is one of the most abundant compounds in the universe. The Kuiper belt, that enormous region of icy bodies out beyond the orbit of Neptune, is said to contain enough frozen water to refill the earth’s oceans many times over.
Human beings consume a lot of water, and only a tiny fraction of the amount we use goes down the gullet as Evian or sweet tea. Most finds its way into various industrial endeavors, such as agriculture, manufacturing and transportation. The City of Phoenix uses around 400 million gallons of water a day in the summer, much of which goes to groom its lawns and ubiquitous golf courses.
The energy industries utilize a lot of water, too. In coal mining, for example, water is used in coal cutting, suppression of dust, and washing of produced coal. When the coal is transported by slurry pipeline, a lot more water is used, though 70% of that is recycled. In thermoelectric generation, water’s role in cooling has been steadily increasing, while in the nuclear power industry, substantial amounts of water are used for both the mining of uranium and its refinement, as well as in the nuclear plants themselves.
Water for oil. Water’s place in petroleum drilling has increased, too. Primary production uses comparatively little water, but with enhanced oil recovery, the wet stuff is the lead player. Secondary recovery by waterflood or steamflood results in not only increased hydrocarbons production, but more produced water. Much of that is reinjected, but there is still a lot of net usage.
Of course, water is the “hydraulic” part of hydraulic fracturing. How much water is used on a given well is the result of a lot of variables—depth, geology, recovery technique and reservoir depletion. On average, millions of gallons are used for each well. In the Haynesville deep shale gas developments, about 600,000 gallons of water are used in drilling a typical well, according to Chesapeake Energy. However, fracturing that same well requires about five million gallons. Similar numbers are found in the Niobrara shale of Colorado, where Ultra Resources has been operating in the Colorado Springs area. Ultra reported that an average of 370,000 gallons of water was required for drilling and fracing a vertical well, but the number jumps to 2.8 million with lateral extensions.
Two events in Texas occurred simultaneously in 2010—an unprecedented shale drilling boom and the most devastating drought since the 1950s. In the Eagle Ford shale region of Texas, where drilling went from nearly zero to over 200 rigs working in just a couple of short years, water availability and cost have been seriously constraining factors, causing companies there to seek out new ways to control its use. ConocoPhillips reported that it has managed to reduce water usage in its Eagle Ford wells to an average 3.57 million gallons, a 30% improvement over previous requirements.
Apples to apples. Comparing relative water usage across industries is difficult, but with energy production, there is a meaningful benchmark. How many gallons of water, net, does it take to produce a million Btu of energy (gal/MMBtu). This is the only comparison that makes sense, when talking strictly about conservation (as opposed to overall cost). A 2010 study by Harvard’s Belfer Center, Water consumption of energy resource extraction, processing and conversion, did just that, comparing various energy industries by their water usage, in gal/MMBtu.
In the U.S., primary oil production is insignificant (this is not primary production country), but what there is uses only 1.4 gal/MMBtu. Secondary recovery, however, utilizes 62 gal/MMBtu, on average. Since that accounted for 80% of total U.S. production (at the time of the study), this is very significant. Tertiary EOR by steam injection utilizes 39 gal/MMBtu, while CO2 injection comes in at a whopping 94 gal/MMBtu. Together, these techniques accounted for about 17% of U.S. production. It’s difficult to break out the numbers specifically for hydraulic fracturing, but EIA estimates this adds 0.6–6 gal/MMBtu to the total.
So-called “oil sands” (or “tar sands” if you’re against it) is all in the news these days, and it is a very water-intensive industry. When it is mined, the water usage is mainly for separation from sand and upgrading of the bitumen to heavy syncrude. Estimates vary, but Wu, et al., of the Argonne National Laboratory, estimates 29 gal/MMBtu. When bitumen is produced in-situ by either cyclic steam stimulation (CSS) or steam-assisted gravity drainage (SAGD), aggressive re-use of water helps reduce net water consumption, leading to 16 gal/MMBtu for CSS and 9.4 gal/MMBtu for SAGD, including upgrading.
Natural gas is a water-miser. For conventional natural gas drilling and production, net water usage per unit of energy is effectively zero. When we start talking about shale gas and tight gas, with multi-stage fracturing, water use leaps considerably, but not as much as the public might think. The big difference is that for this type of natural gas production, the water usage is “up front,” as it were. That is, water is used in the drilling and completion phases, and so the gallons of water per unit of energy is a function of ultimate gas recovery. This varies greatly across the four main shale gas plays in the U.S., but is still low compared to other fossil fuels. Chesapeake estimates that water intensity in its gas production ranges from an average 0.8 gal/MMBtu in the Haynesville to 1.7 gal/MMBtu in the Fayetteville play.
Water usage per se has been a local issue. The really sticky questions relate to groundwater contamination, which is where most of the push-back from communities and environmental groups has occurred. As far as overall water usage is concerned, drilling and fracing are factors, but compared to the vast scope of human activities, they just don’t stand out. 
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