There's been a lot of good news recently about water and hydraulic fracturing.
♦ The Environmental Protection Agency (EPA) recently released a major study finding no instances of water contamination by the hydraulic fracturing process - and only rare instances of groundwater impacts from the broader elements of oil and gas development.
♦ EPA's and other scientists' research into water consumption for hydraulic fracturing found minimal strain on water resources.
♦ Finally, natural gas power generation, which has surged because of the growth in hydraulic fracturing, significantly reduces water use in power generation.
The EPA draft report, “Assessment of the Potential Impacts of Hydraulic Fracturing for Oil and Gas on Drinking Water Resources," is essentially a 998-page literature review of the full lifecycle of water involved in hydraulic fracturing, from water acquisition to wastewater disposal.
The report does identify numerous potential situations where drinking water contamination could occur, but identifies only a small number of instances of contaminated drinking water wells caused by surface spills of hydraulic fracturing fluid, or flowback or produced water.
To put this in perspective, EPA tallied 25,000 to 30,000 hydraulically fractured wells per year from 2011 to 2014.
A major complaint by the environmental community is that the study conclusions are unjustified because of a lack of data due to industry's refusal to participate in longitudinal studies. However, EPA states that it has a cooperative relationship with industry.
At the same time, other environmentalists complain that the energy industry was too involved - even to the point of controlling the study.
Water consumption has attracted public concern as population growth, increasing agricultural requirements or drought strain available water supplies.
The U.S. Geological Survey, in an analysis of well data from 2000-14, reported that hydraulic fracturing of the average horizontal oil well used slightly more than four million gallons of water. Horizontal gas wells averaged about 5.1 million gallons.
Actual water consumption for a particular well varies based on factors including the rock properties, the length of the horizontal leg, the number of separate fracturing stages and the composition of the fracturing fluid.
Water used in hydraulic fracturing can come from surface waters, groundwater aquifers or recycled wastewater. Decisions on water acquisition depend on locally available sources - transporting water is expensive. Generally, surface water is the major source in the eastern United States, and groundwater is used in western states with little available surface water.
Texas hydrologists report that surface and groundwater each supply about half of water used for hydraulic fracturing of the Barnett shale around Dallas-Fort Worth; reuse/recycling provides about 5 percent and brackish water is 3 percent of waters used to stimulate the Barnett shale.
How much of a strain this use places on other water users depends to a large part on the population density, the agricultural or industrial demand for water, and the available water volume.
For example, the EPA conducted case studies of water use in Pennsylvania's Susquehanna River basin, where they found that water management prevents overuse and minimizes risks to individual sources. In the Marcellus shale area, which includes the Susquehanna River basin, essentially all produced water is reused - but that makes up only a small percentage of the amount needed for new well stimulations.
EPA also studied the hydraulic fracturing water use in the Piceance basin within the semi-arid Upper Colorado River basin in Colorado. There the industry reuses 100 percent of large volumes of flowback water and requires very little freshwater.
Obviously, drought conditions impact all water users. After heavy rains in Texas this spring, California is the only major oil and gas producing state experiencing extreme drought conditions - and many Californians are unhappy about water use for hydraulic fracturing, although the industry uses little water: 70 million gallons, 140,000 gallons per well, or about 0.004 percent of what California households use annually (California Council on Science and Technology).
Texas has large numbers of hydraulically fractured oil and gas wells, and its Bureau of Economic Geology (BEG) hydrologists have studied the impact of hydraulic fracturing on local water supplies. In June, BEG senior research scientist Bridget Scanlon presented some of this information at House and Senate briefings organized by the Washington, D.C., geoscience consortium that includes AAPG.
She reported that in the Eagle Ford play of semi-arid west Texas:
- Hydraulic fracturing accounted for 16 percent of total water consumption in 2013.
- The dominant groundwater use for 2013 was for irrigation, which consumed 62-65 percent.
- Between 10-12 percent of the groundwater went to municipal use.
- Steam electric power plants took 7-13 percent.
The BEG hydrologists have a cautionary conclusion for the Eagle Ford play:
“While regional impacts of water pumpage to support HF are small, localized impacts can be large with estimated water level declines of approximately 100-200 feet in about 6 percent of the western play area."
This column ends with good news for water supplies: Natural gas power generation reduces water use by up to 60 percent relative to coal and nuclear plants.
This has a big impact on water withdrawals for power plants that traditionally make up 38 percent of water withdrawn from U.S. lakes and rivers.
This also reflects the fact that the majority of gas-fired electricity is produced by gas turbines, which do not use steam to drive turbines, or by combined cycle plants, where the waste heat from gas turbines (that do not use water) goes to steam generation units.