Water use in the oilfield is the center of one of the most contentious debates in energy. It’s easy to see why: when you hear that millions of gallons of water are used to frac a single well, you take pause. Millions of gallons sounds like an awful lot of water, and since thousands of wells get fracked in a year, one can make a quick conclusion that billions of gallons of water are forever lost to future use on the Earth’s surface. In addition to the sheer volume of water that gets used, the notion of taking billions of gallons of fresh water, adding chemicals, pumping it into the earth, and getting out a toxic mess of chemicals, salt, radioactive compounds and hydrocarbons makes for even more suspicion about water use in oil and gas.
When considering water use in the oil patch, it’s incredibly important to understand scale. Between 6 and 7 billion of gallons of water get used every year to produce oil and gas. This compares to the nearly 2 trillion gallons used to keep America’s golf courses green, an arguably much less valuable use of water in the global sense of things, but far less contentious. In fact, in all of the data that we have analyzed for oilfield water use across the country, we have found that water used for oil and gas production accounts for no more than 5% of a state’s total consumption. In many of the largest producing states, it accounts for less than 2%. While golf course irrigation is straight forward (apply a million gallons of water a day to a single course, get lush green grass in the middle of sun-scorched Arizona), water use in oil and gas is far from easy to understand. Water use in the oil field is complicated, often play-specific and water has constantly a changing lifecycle in the oilfield. The complicated nature of the oilfield water lifecycle is a key reason that people get so up in arms about how much water gets used to produce oil and gas. This is the first in a series of posts in which I’ll try to shed some light on how water gets used in the oil and gas production process and how the industry’s constant development of new technologies is changing the lifecycle of water in the oilfield.
The Oilfield Water Lifecycle from 50,000 ft.
Most water used in the oilfield starts in the same places as water used on golf courses, households and farms: it is sourced from a ditch, a stream, a reservoir or a well tapping groundwater. While some producers own their own water and hire truckers or build pipes to access it, many buy it from water developers at loading depots (loaded onto trucks), or buy it directly from a service company that also manages their water logistics. Since large quantities of water are needed on short order, most fresh water goes from the source to holding ponds or tanks to ensure that enough supply is immediately available when demand hits. The fresh water then typically gets picked up from the source or storage by caravans of trucks or piped out to the oil field.
Oilfield water logistics get complicated fast – there are a lot of different ways water gets handled, and this is the part of the water lifecycle that is changing the most. Every producer or service company employs a slightly different model for water handling. Different producing plays require varying amounts of fresh water and produce water of varying quality. With so many moving parts to consider, let’s start by zooming out and looking at the whole lifecycle.
Figure 1 shows the typical lifecycle of water. After water gets to the field or well site, it is typically held in storage, again because water use is immediate and not gradual. Having stored water on hand allows drillers to operate without waiting on supply. Drilling is when the first large volume of water gets used. In general, water used in drilling accounts for up to 20% of the total water used at a well site. This can range from around 30,000 gallons to over 1 million. Drilling phase water use ranges from fluid and cement preparation to rig washing and sanitation at the site.
Well completion, the phase of development when fracking happens, is the most water intensive part of the oilfield water lifecycle. In most horizontal wells, between 1 and 5 millions of gallons of water gets used in the completion process to stimulate the rock formation. Fracking is one of the methods of stimulation. A great informational video to explain the process can be found.
After completion, water handling gets especially complicated. After a well is fracked, between 20-80% of the mixture used in the process flows back up the well to the surface; this is called flowback water. Flowback water is far from fresh at this point, containing not only the chemical additives put in it for the well stimulation, but also compounds that existed in the fractured rock formation and dissolved in the water mixture. Every formation (even different regions within each formation) requires different amounts of water and chemical mixtures, produces different amounts of flowback and importantly, has different kinds of compounds in its flowback volumes.
Water recovered after use in drilling and completion is often kept in pits, ponds or storage tanks. From there, it can go a number of places. It may be left to evaporate for a period of time or is transported for disposal or treatment. Historically, this water was most often transported by truck to an injection facility, where it was disposed of by injecting it into a very deep disposal well. A significant amount of waste water is still disposed of by this means, but advances in technology have facilitated a steep rise in the amount of water that can be treated and reused in future well stimulations.
Treatment technologies have advanced significantly over the last few years – enough that I will devote an entire post to understanding their impacts in the near future. Treatment can be used to clean water so that it can be released into streams or injected into the sub-layers of soil, trucked or piped to various disposal facilities, or reused in the oilfield. Treated water that will be recycled at the well site typically goes to storage facilities at the site, where it is often blended with fresh water to further it. While this still requires fresh water, the amount is much less than for a conventional all-fresh water completion. Some producers have been able to use as much ase 80-90% recycled water, saving millions of gallons of fresh water per well. In some areas, recycled water goes straight to reuse at a new well site with virtually no blending at all.
While oil and gas production does require a significant amount of water, the industry has made great strides in reducing its freshwater needs, and will continue to do so looking forward. Stay tuned to Currents as we dig into the issues of moving water in the oilfield, the impact of new water treatment and fracking technologies, and much more.