Because water is such a versatile resource that is critical for so many daily uses, different end-use sectors leverage the resource in different ways and in different quantities. The USGS publishes water use data every five years. Data from 2020 is expected to be published sometime in 2023. For now, we can refer to the most recent data published for 2015.
Water’s versatility also leads to vast geographic demand disparities depending on where people live, which industries are common, and how available water is. In 2015, more than a quarter of all water withdrawals came from only four states: California, Texas, Idaho and Florida.1USGS, 2019, Trends in Water Use, https://www.usgs.gov/mission-areas/water-resources/science/trends-water-use (accessed December 20, 2022).
You will notice in the map above, that several of the states with the highest water withdrawal rates are energy producing states. One of our experts explains the intersection of water and the energy sector in the video below, especially as it relates to the role of water in unconventional oil and gas production. In her discussion, water withdrawal for the mining sector includes water used in hydrocarbon extraction, including conventional and unconventional production methods, combined with water used for mining such as copper, uranium and salt. The total of all of these uses has remained fairly constant since 2010 (shale boom data) and is about 1% of total withdrawals in 2015.
Transcript
Role of Water in Oil & Gas Extraction – Bridget Scanlon – The University of Texas at Austin
Water and energy are integrally related. In order to seek, extract, convert, deliver and consume energy, we need water. To extract, treat, store and deliver water, we need energy. Without water, there would be no energy. And without energy, no water. At least in the forms our society can leverage. In oil and gas operations, water plays a key role in exploration, production, transportation and refining. Let’s talk about how water is used specifically in energy extraction.
What’s the most common fluid that the petroleum industry produces? You may be surprised to know it’s not oil, but water. The oil and gas industry produces about 10 times more water than oil. However, oil and gas extraction also requires water for both conventional and unconventional extraction. Therefore, water management presents two obstacles for operators: Where does it come from before and where does it go to after extraction?
For over 100 years, water has been used to produce oil and gas from conventional reservoirs, mostly by water flooding to enhance production after the initial reservoir pressure declines. Produced water, along with additional surface water or groundwater, is often injected into the formation to increase the reservoir pressure and maintain production levels. Water associated with production from the reservoir is injected back into it during a water flood operation.
Water is a much bigger issue for oil and gas production from unconventional reservoirs than conventional reservoirs because of the large upfront water requirements for hydraulic fracturing. Also, larges volumes of flow back and produced water from the well cannot be re-injected into the producing reservoir because of low permeability.
What are the dominant sources of water for hydraulic fracturing? In humid regions in the eastern United States, water is derived mostly from streams and rivers and produced water is reused for hydraulic fracturing. In more arid regions in the western United States, the dominant water source is groundwater. With advances in hydraulic fracturing fluids, more brackish and saline groundwater is being used. Produced water, with up to three to four times the salinity of seawater, can also be used.
Reuse of produced water serves two purposes: reducing stress on freshwater resources and reducing the volumes of produced water requiring disposal. However, reuse may increase the risk of contamination.
Is water management for oil and gas extraction improving? There have been significant advances in water management for unconventional oil and gas production. Examples include reuse of produced water in the Marcellus Shale play. Over 90% of the produced water is reused for hydraulic fracturing and this water accounts for up to 20% of the water required for hydraulic fracturing. Artesian brackish groundwater is being used instead of fresh groundwater in some regions of the Eagle Ford play. Using non-fresh artesian water reduces strain in freshwater resources and the energy required for pumping. Reuse of produced water is also increasing in the Permian Basin, where produced water volumes exceed the volume of water required for hydraulic fracturing.
Advances in hydraulic fracturing fluid design allow use of untreated produced water. Reported costs by some operators associated with reuse of produced water are similar to or less than costs incurred by sourcing and disposing of water.
One of the big questions is how does water use for hydraulic fracturing compare with using in other sectors? In many shale plays, water used for hydraulic fracturing is a small percentage of total water used in the play area, particularly in dry regions where most water is used for irrigation, such as the Permian Basin in west Texas.
Let’s consider some numbers to put the water usage into perspective. In 2010, water used for all U.S. mining and extraction, including shale gas production, accounted for only 1.5% of all water use. Cooling power plants in the U.S. required about 15 times the water required for extraction of shale gas in the Marcellus and Eagle Ford plays.
Water usage statistics reflect just how integral water is to unconventional oil and gas production. The median water volume used to fracture horizontal wells increased almost tenfold within the past decade, partly due to increased well lateral length. This increase in use of water for hydraulic fracturing, combined with the management of produced water, will remain a challenge for the industry. But improvements in technology and infrastructure development should continue to enhance water management and help the industry meet these water challenges in the future.
Citations
Map: USGS, Total Water Use Withdrawals in 2015, https://www.usgs.gov/media/images/total-water-use-withdrawals-2015 (accessed December 20, 2022).
Images: “Irrigation” by Brad Smith licensed under CC BY NC 2.0