Some simple types of hydraulic fracturing techniques have been used on a small scale in oil and gas production for decades. However, hydraulic fracturing operations in recent years have become more complex, involving the exploration of and production from significantly deeper formations and across much larger subsurface areas through the use of horizontal drilling techniques. The development of horizontal drilling, combined with hydraulic fracturing, has made the production of oil and gas from shale feasible.
Hydraulic fracturing or fracking as it is more commonly known involves the pressurized injection of fluids made up of mostly water and 1-2% chemical additives to change the viscosity of the water into a geologic formation. These chemicals can serve many functions in hydraulic fracturing, including limiting the growth of bacteria and preventing corrosion of the well casing, and the formulation used varies. The water and chemicals are injected at high pressure that exceeds the rock strength and the fluid opens or enlarges fractures in the rock. As the formation is fractured, a “propping agent,” such as sand or ceramic beads, is pumped into the fractures to keep them from closing as the pumping pressure is released. The fracturing fluids (water and chemical additives) are partially recovered and returned to the surface and recycled, stored or deep well injected for disposal. Natural gas or oil will flow from pores and fractures created in the rock into the wells allowing for enhanced access to the methane or oil reserves. While fracking techniques used decades ago involved 100,000-300,000 gallons of water mixed with chemical additives, a modern fracking can use 3,000,000-5,000,000 gallons of water mixed with chemical additives.
Over the past 10 years, there have been significant technological advances in horizontal drilling. Hydraulic fracturing and horizontal drilling combined together can release significant quantities of oil and gas from large shale deposits, and has led to oil and gas production in parts of the country that had not previously produced significant amounts of oil or gas. This has produced a rapid increase in fracking across the United States to areas without adequate regulation and safety protocols for widespread oil and gas drilling. Regulation of gas and petroleum exploration has remained primarily with the states.
Fracked oil and gas can result in an economic boom as it generates income. If fracking is done carefully and properly the safely extracted gas can reduce air pollution and even water use compared with other fossil fuels. However, the availability of vast quantities of natural gas is likely to slow the adoption of renewable energy sources and, if fracking is done poorly toxic chemicals from fracking fluid could be released into our water supplies and methane could be release to the air.
There is a moratorium in New York State on fracking based on health and environmental concerns and Maryland is considering a 3 year moratorium on fracking. The moratorium is in response to concerns that include air pollution from the operation of heavy equipment, human health effects for workers and people living near well pads from chemical exposure, noise and dust, induced seismicity from the disposal of fracking fluids, and increased greenhouse gas emissions from poor well head control and continued use of hydrocarbons. However, the biggest health and environmental concerns remains the potential for drinking water contamination from fracturing fluids, natural formation waters, and stray gases.
A significant concern is the amount of water needed to hydraulically fracture a well. On average takes 3.8 million gallons of water for each well. Though about half the water will be returned, the recovered water will contain chemical and radiological contaminants and this water needs to be properly treated and/or disposed of. Though, surprisingly, shale-gas extraction and processing are less water intensive than many other forms of energy extraction. The water intensities for coal, nuclear, and oil extraction are approximately 2 times, 3 times, and 10 times greater than for shale gas, respectively. Corn ethanol production uses substantially more water because of the evapotranspiration of the plants, and 1,000 times more water than shale gas if the plants are irrigated. Conventional natural gas uses less water and renewable forms of energy such as wind and solar that consume almost no water.
Maintaining well integrity and reducing surface spills and improper wastewater disposal have been found to be the way to minimize contamination from the chemicals used in fracking fluid and from naturally occurring contaminants such as salts, metals, and radioactivity found in oil and gas wastewaters that are returned to the surface. Though, there have been few definitive studies of the frequency, consequences, and severity of well integrity failure. Studies done in Ohio and Texas found over a 25-year period on a mix of traditional and shale gas wells found an extremely low level of incidence of groundwater contamination, In Ohio they found 185 cases of groundwater contamination caused primarily by failures of wastewater pits or well integrity out of about 60,000 producing wells, for an incident rate of about 0.1%.The rate for Texas was found to be even lower at about 0.02%, The Texas study included 16,000 horizontal shale-gas wells with none reporting groundwater contamination.
A significant concern among the public is that hydraulic fracturing could open small cracks thousands of feet underground, connecting shallow drinking-water aquifers to deeper layers and providing a pathway for the chemicals used in fracking and naturally occurring geological formational brines to migrate upward. In practice, according to research performed in Pennsylvania this is unlikely because of the depths of most (but not all) shale formations tends to be 3,000-10,000 feet below ground level, and man-made hydro-fractures rarely propagate more than 2,000 feet. According to scientists who have studied fracking a more plausible scenario would be for man-made fractures to connect to a natural fault or fracture, an abandoned well, or some other underground pathway, allowing fluids to migrate upward). A simpler pathway for groundwater contamination, though, is through poor well construction and integrity, which was found in drinking water contamination overlying the Marcellus Shale in Pennsylvania.
The number of peer-reviewed studies that have examined potential water contamination is surprisingly low- barely a handful. Wastewater from oil and gas exploration is generally classified into flowback and produced waters. Flowback water is the fluids that are return to the surface after the hydraulic fracturing and before oil and gas production begins, primarily during the days when the well is completed. Typically it consists of 10–40% of the injected fracturing fluids and chemicals pumped underground that return to the surface mixed with an increasing proportion of natural brines from the shale formations over time. Produced water is the fluid that flows to the surface during extended oil and gas production. It primarily reflects the chemistry and geology of deep formation waters. These naturally occurring brines are often saline to hypersaline and can contain toxic levels of elements such as barium, arsenic, and radioactive radium. Little is actually known about how naturally occurring brines flow through formations.
In response to public concern the US House of Representatives requested that the US Environmental Protection Agency (EPA) examine the relationship between fracking and drinking water resources in 2009. In 2011, the EPA began a series of research projects into the impacts and potential impacts of fracking on water. Also, in April 2012 EPA released the first federal air rules for natural gas wells that are hydraulically fractured, requiring operators of new fractured natural gas wells to use “green completion,” which is a series of technologies and practices to capture natural gas and other volatile substance that might otherwise escape the well during the completion period when most volatile release takes place. The latest reports found this to be very effective.
Whether the EPA will regulate oil and gas exploration nationally or leave the oversight in the hands of the states is an open question. However, the Bureau of Land Management has taken steps to regulate fracking on public land. On Friday, March 20, 2015, U.S. Secretary of the Interior Sally Jewell announced the final rule for hydraulic fracturing on federal and tribal lands. This rule establishes new requirements to ensure wellbore integrity, protect water quality, and enhance public disclosure of chemicals and other details of hydraulic fracturing operations. This final rule will supplement the existing regulations for drilling on federal lands. The George Washington National Forest is the largest protected forest in the eastern United States at 1.1 million acres in the mountains of Virginia. Approximately half of the forest sits atop the Marcellus shale deposit. Oil and gas drilling using hydraulic fracturing or any other approved method is allowed in the 16% of the forest with existing leases and privately owned oil and gas rights.
Virginia has entered this debate. Natural gas deposits are located within certain areas of the Commonwealth. The use of fracking has a long history in Virginia going back to the 1950s. A nitrogen-based foam has historically been used in the fracking process here. Currently, there are more than 7,700 natural gas wells in the Appalachian plane where drilling required fracking in the extraction process. To date, there have not been any reports of adverse effects on water quality from the fracking. The other environmental impact of an industrial process is not much different from coal mining, dust, constant truck traffic, noise. The expansion of coal bed methane production has been in rural Buchanan and Dickenson counties.
However, there are other areas in Virginia that have methane reserves that could be accessed by fracking. The Taylorsville Basin is located north of Richmond and extends across the Virginia Coastal Plain in the tidewater region of the state. The U.S. Geological Survey estimated that the area could contain up to 1.06 trillion cubic feet of natural gas, not huge, but worthwhile economically. Shore Exploration, a Texas-based energy company, has reportedly leased the mineral rights from more than 80,000 acres in Virginia’s Northern Neck and Middle Peninsula spanning large sections of King George, Caroline, Westmoreland, Essex, and King and Queen Counties.
Currently, Virginia law prohibits drilling in the Chesapeake Bay waters and all of the tidal tributaries, but outlines the path for drilling to proceed in the non-prohibited areas of the tidewater region. Whether or not to allow drilling in areas that are not areas identified as part of the Chesapeake Bay waters and tidal tributaries is a regulatory decision, controlled by the Virginia Department of Mines, Minerals and Energy (DMME). Basically, in order to grant a permit, DMME must undertake an environmental impact assessment in consultation with the Virginia Department of Environmental Quality (DEQ). However, DMME is only obligated to consider the findings of the assessment, and ultimately maintains the full authority to issue the permit. Local communities that might be significantly impacted by truck traffic, there is no pipeline, no source of water for a hydraulic fracturing so thousands of truck loads would have to run on small rural roads.