Fracking involves injection of a liquid that is usually a mixture of water, sand and chemical additives.
What is it:
Fracking, or hydraulic fracturing, is a process used by many oil and gas recovery operations. It involves injection of a liquid that is usually a mixture of water, sand and chemical additives.
The injection is under pressure so it causes fissures or cracks in the underground formations, and that allows release and recovery of oil and gas that often would not be recoverable by other means.
It could be applied in older spent wells to increase their yields, or in new wells where oil and gas production would not otherwise be feasible.
Fracking was originally introduced in the 1940s, and more than 100,000 individual hydraulic fracturing treatments had been applied by 1955 and many more since.
The technology has undergone recent major improvements that have made it much more attractive and productive and much more widely practiced.
Where is it:
Due to those more recent technological improvements, which include horizontal drilling and multi-stage hydraulic fracturing within a horizontal well, fracking has been applied in many locations around the U.S. that were never considered to be energy producing, and U.S. oil and gas production has increased rapidly.
Production of shale oil has increased more than fivefold from 39 million barrels in 2007 to 217 million barrels in 2011.
Suitable shale oil and gas locations are identified using seismic exploration methods. Some of the major U.S. shale plays are: Barnett, North Texas; Fayetteville, Ark.; Haynesville, La. and East Texas; Marcellus, Northeast U.S.; and Woodford, Okla.
Not all deposits are recoverable. The Marcellus shale area holds one of the largest technically recoverable shale gas deposits — up to 227 trillion cubic feet. The Bakken formation in North Dakota has recently become a very productive oil producing area. There are numerous other areas under exploration, however, the recovery potentials differ due to geologic conditions.
Estimates of technically recoverable shale oil in the U.S. are as high as 33 billion barrels.
How is it done:
The overall process consists of clearing and leveling the area and constructing a pad where the drilling rig will be located.
Often roads and other infrastructure must be constructed. Then, the drilling and well construction occur, the fluids are produced and pressurized hydraulic fracturing is utilized.
Potential health and environmental effects:
By law, wells must be drilled below freshwater aquifers and cased to prevent contamination of those aquifers by the fluids and additives as well as by water from the deeper aquifers.
Fracking involves injection of large volumes of the hydraulic fluid. Much of that is recovered along with deep, often saline, groundwater that surfaces and must be processed and safely disposed or reused.
That groundwater sometimes contains contaminants like radionuclides or bromide.
The fracking fluids contain many additives, which if not controlled can result in releases and environmental damage. These include hydrochloric acid, biocides, corrosion inhibitors, borate salts, friction reducers, gelling agents, potassium chloride, oxygen scavengers, scale inhibitors and surfactants.
Air quality degradation can occur in the vicinity of drilling sites because of engine exhaust and from flaring or venting of natural gas as well as from particulate releases.
There are water quality risks from contamination of ground and surface waters from spills and releases.
Freshwater used in drilling could range from 100,000 to 600,000 gallons, or more, per well. The hydraulic fracturing could consume 5,000,000 gallons per site. The sources could include local streams and groundwater, municipal water, reused industrial or municipal wastewater or water recycled from the process.
Onsite water treatment is being practiced to a greater degree, and some locations require transport to a central location for treatment prior to environmental releases.
Increased seismic activity has been suggested as a problem from fracking operations, however, others have suggested that waste disposal wells are more likely causes.
Water treatment:
Numerous water treatment processes can be employed to render the wastewaters usable onsite and others to upgrade it so it can be discharged to surface waters. Some remove residual oil, others separate solids that can be disposed of in landfills.
Desalination type processes, including membrane distillation, are being applied.
Regulation:
In general, fracking can be carried out without causing environmental damage. Oil and gas production activities are regulated, and considering the extent and diversity of those activities the record of performance appears to be fairly good.
Most aspects of oil and gas development, including well siting, drilling, casing, cementing, etc., are covered by state laws. Many activities are exempted from the Clean Water Act National Pollutant Discharge Elimination System (NPDES) stormwater permits for uncontaminated runoff. However, many states regulate these more stringently than federal requirements.
Fracking is indirectly regulated to some degree by the Underground Injection Control requirements under the Safe Drinking Water Act, but the Energy Policy Act of 2005 excluded hydraulic fracking per se from underground injection.
Disposal of oil and gas wastewaters are regulated by NPDES standards for discharges to surface waters. Pretreatment is often required at an industrial treatment site.
Many oil and gas wastewaters are disposed of by underground injection and these are covered by the Underground Injection Control programs by states and Environmental Protection Agency regions if the state does not have enforcement primacy.
The federal government is considering new legislation to provide additional safeguards, but the need for more federal legislation will surely be debated in Congress.
Dr. Cotruvo is president of Joseph Cotruvo and Associates, LLC, Water, Environment and Public Health Consultants. He is a former director of the U.S. EPA Drinking Water Standards Division.
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