Prior to 1980, the production and development of oil and gas came from wells that were drilled vertically. As the wells were drilled core samples were examined to determine what type of rock layers were at various depths. Some layers had porous rock such as sandstone while other layers were very dense. Because oil and gas can seep through porous rock, the well was completed in the layers which were porous, and the sides of the wells between completion locations were protected by long sections of metal pipe, called the well casing. In order to prevent materials from traveling between the casing and the rock up or down the well, the drilling company typically poured cement into the gap between the casing pipe and the outer diameter of the well bore.
Because sandstone had tiny pours, oil and gas that were trapped in the rock layer could flow easily into the well. The problem with this approach was that if the well site was not exactly over an underground pocket of oil or gas, the well would be a "dry hole" that did not produce any valuable petroleum. Drilling dry holes wasted a lot of time and money for the oil and gas producers. By the 1980s, most of the easy-to-access oil and gas on the onshore lower 48 states had been drilled, and imports continued to climb.
Two new technologies became popular after 1980. First, computer-controlled drill bits were used to bend the direction of new wells. Instead of going straight down, the wells could go down until a particular rock formation was reached and then the well could turn and run for miles parallel to the surface. Even if the well was not started exactly over an oil or gas deposit, it became more likely that the well would travel through a deposit at some point along the horizontal part of the well. Second, drillers learned how to fracture the rock next to the completion locations of the well. By making tiny cracks in non-porous rock, oil and gas that was trapped in those dense rock layers could flow into the well, just as if the rock was porous.
Fracking involves forcing a large amount of a mixture of water, sand and special chemicals into the well at great pressure. The mixture has to go somewhere, so it finds the completion locations where there is a gap in the casing pipe and breaks up cracks into the surrounding rock layer. The pressure transmitted through the mixture fluid is like hitting the rock layer with a heavy hammer. If a producer tried to frack a vertical well, it would not produce very much petroleum, because only the oil and gas trapped within just a few feet of the well would be released by the small cracks. However, a horizontal well has many openings in the rock layer, making it possible for one well to release a lot of gas from the new cracks at the series of openings along the horizon portion of the well.
Because this new technology allowed the production of gas from non-porous shale rocks that had previously been considered to be undesirable for oil and gas production, the supply of onshore gas increased and the market price for gas dropped.
At current prices, fracking provides a fuel for generating electricity that is cleaner and cheaper than coal. This lowers the amount of air pollution from making electricity. However, some people argue that fracking also poses environmental risks. First, some drillers do not properly dispose of the fracking fluid mixture after the well is done. Second, people are now drilling wells in places that did not historically have oil and gas wells. One of the first successful places which used fracking was the Barnett Shale near Ft Worth, Texas. Wells were drilled from locations along the Trinity River near the downtown part of that city. Third, some wells do not properly cement the gap between the well casing and the surrounding rock. Historically, shale rock separated the rock layer that supplied water wells with drinking water from other porous layers that held oil and gas. Without cement, and with more cracks in the shale layer, it is possible that some gas can travel into the rock layer holding the water and contaminate it. Fear of drinking water contamination or destruction of natural land led some voters to argue that fracking should be banned. The Obama Administration proposed regulation of fracking on federally-owned lands. Producers argue that if the drilling contractors do their jobs properly, these forms of environmental damage can be avoided.
Although fracking has been used to complete wells since 1947, it did not draw public attention and criticism until recent years. In 2010, the Josh Fox movie "Gasland" caused the general public to question the safety surrounding fracking and created a bit of panic among environmental activists. It shows a water tap that could be ignited by entrapped methane. This prompted the natural gas industry to release a rebuttal film called "Truthland". The debate has lead environmental activists to call for bans or moratoria on fracking specifically or oil and gas well drilling more generally.
On March 18, 2014, a referendum on fracking in southern Illinois won in a landslide. Fracking has brought prosperity to Pennsylvania, where it is allowed, and is controversial in New York and New Jersey, where it is banned by statewide moratoria and some local ordinances.
In Colorado, two towns enacted fracking bans, which were overturned by the Colorado Supreme Court.
Each drilling company has its own secret recipe for the mixture that it uses to frac wells. Each company claims that by adding chemicals to the water and sand mixture, more cracks will be made and a better flow of oil or gas will result. There is a nationwide battle of whether the drilling companies can keep their recipes secret. Wyoming was the first state to requiring drilling companies to file their list of fracing fluid ingredient with state regulators. Environmental groups then sued to get public disclosure of those recipes. On March 12, 2014, the Wyoming Supreme Court remanded the lawsuit to make the drilling companies prove that their recipes were protected "trade secrets." The American Legislative Exchange Council (ALEC) together with ExxonMobil have developed model legislation for states to adopt that would require the recipes to be filed with state agencies but withheld from public disclosure as trade secrets. The US Environmental Protection Agency cannot regulate fracking in order to protect groundwater, because a 2005 law exempted fracking from the Safe Drinking Water Act, which controls how industries inject substances underground.
The same people that say man is causing Global Warming are now claiming that hydraulic fracturing is causing earthquakes and pollutes water supplies. Liberals are anti-oil and will do anything to stop America from creating more oil chiefly because of the atmospheric pollution it is associated with. Those organizations with an agenda and money will continue to spread lies in order to achieve a ban, despite the lack of evidence.  In 2015, the EPA ruled that fracking was not a hazard to water supplies.  This didn't stop the Governor Andrew Cuomo of New York from banning fracking in his state.
The study frequently cited by advocates of fracking bans was authored by Cornell University scientists Robert Howarth and Anthony Ingraffea which set high estimates on the amount of methane released during the drilling and development of gas wells that are fracked. However, this study has been widely criticized by subsequent research.
Stanford university Geophysicist Mark Zoback stated that the amount of energy released in a microseismic event, for which fracking equals, "is equivalent to the energy of a gallon of milk hitting the floor after falling off a kitchen counter." 
There is some evidence that the pumping of waste water into shale formations, the process after oil and gas extraction, can cause tremors. The evidence is so far inconclusive but seismic readings suggest this might be the case. Waste water has been pumped deep underground for more than 50 years, long before fracking was invented.
- Broder, John. "New Proposal on Fracking Gives Ground to Industry", New York Times, May 4, 2012. Retrieved on March 18, 2014.
- Truthland View The Movie. Retrieved on May 5,2016.
- NJ city bans fracking
- Boyce, Dan. "CO Supreme Court Strikes Down Local Fracking Bans", May 2, 2016. Retrieved on May 4, 2016.
- "Wyoming High Court Remands Fracking Secrets Case", Associated Press, March 12, 2014. Retrieved on March 19, 2014.
- Currier, Cora. "ALEC and ExxonMobil Push Loopholes in Fracking Chemical Disclosure Rules", ProPublica, April 24, 2012. Retrieved on March 19, 2014.
- Fracking’s Earthquake Risks Push States to Collaborate, Bloomberg.com, march 27, 2014
- http://www.nationalreview.com/article/419418/even-obamas-epa-now-admits-fracking-hasnt-harmed-water-supplies-jillian-kay-melchior Even Obama’s EPA Now Admits Fracking Hasn’t Harmed Water Supplies, National Review, June 15, 2015
- Entine, Jon. "University Of Texas-Environmental Defense Fund Shale Gas Study Unmasks Politics Of Anti-Fracking Activist Cornell Scientists", Forbes, September 18, 2013. Retrieved on May 4, 2016.
- Does fracking cause earthquakes?, DailyCaller.com, march 19, 2014