This practice is controversial as many of the chemicals used are alleged by opponents to be toxic or carcinogenic and those activists that are against the method argue that it releases methane and harmful chemicals into nearby ground water. There is a growing movement, especially in Colorado, to impose bans on the use of fracking, often through local ballot measures and through a possible statewide measure in 2014.
Horizontal wells have become important to the oil and gas extraction process because they allow drillers access to oil and gas resources that were previously unreachable. Drillers are able to drill straight down and then turn the drill bit horizontally, increasing how far underground each oil and gas well can reach. While the first horizontal well was drilled in 1929 in Texas, it was not until the 1970s through the invention of downhole motors that allowed drilling to be better controlled by oil and gas operators. The use of horizontal wells over traditional vertical wells can reduce surface disturbance by up to 90 percent.
History of fracking
Fracking has become important to the oil and gas extraction process because it allows drillers access to oil and natural gas resources that were previously either unreachable, or economically unfeasible to produce. The predecessor to modern day fracking, the "Exploding Torpedo," a method of fracturing the rock in a well to increase oil and gas extraction, was developed by Lieutenant Colonel Edward A. L. Roberts. Roberts, a Civil War veteran, patented his system on April 25, 1865. The idea came to Roberts during the Battle of Fredericksburg as the Lieutenant Colonel saw the effects of torpedoes as they hit the nearby river and thought he could use a similar system to increase oil and gas extraction from wells. Roberts used 15 to 20 pound torpedoes, with a small cap on top, that when connected to the top of the shell could be used to control the blast. After lowering the torpedo down a well he would cover the borehole with water to increase the effectiveness of the blast. The system Roberts patented was revolutionary because he replaced the gunpowder traditionally used in torpedoes with nitroglycerin. Using this method, Roberts was able to increase oil and gas extraction by as much as 1,200 percent. This method for fracking wells was used until 1990, since then hydraulic fracturing has become the industry standard.
The modern version of fracturing wells was used experimentally in Kansas in 1947, and commercially by Halliburton in 1949. Then, in 1970, downhole motors were developed, leading to the ability to drill wells horizontally. These technological advances were furthered by research done by the U.S. Department of Energy, Mitchell Energy Company and the Gas Research Institute during the 1980s. This research improved the knowledge of and technology around horizontal drilling, fracture designs and the characterization of oil and gas reservoirs.
The following outlines the general process for fracturing a well, from locating oil and gas resources to well completion and cleanup. These processes, as well as the amount of water, chemicals and proppant vary from well to well depending on the geological makeup of the well.
Surveying and permitting
- A shale play is found with enough resources that oil and gas operators are willing to invest millions of dollars to look for economically recoverable oil and gas resources.
- Land is leased: private land leases are negotiated with landowners and federal and state lands are leased through state or federal land agencies.
- Seismic surveys are done to identify where the oil and gas resources and water are located using sound waves. In some cases explosives are used to create waves and geophones read the waves. Large trucks known as thumper trucks can also be used to generate vibrations.
- Supercomputers read these data and create images that geoscientists interpret to locate oil and gas resources.
- Oil and gas operators apply for permits. Generally, permits are only valid for a certain period time, usually no more than five years.
- Roads are constructed to allow the trucks and other machinery access to the well site.
- The site is flattened, covered with crushed stone and plastic liners to protect the land underneath from the heavy machinery and other potential impacts.
- Pits are also constructed to hold water. Some companies use steel tanks instead of storage pits. States may regulate the type of storage pits and tanks allowed.
Drilling and casing of the well
During the drilling and casing of a well the goal is to isolate the available hydrocarbons from any freshwater resources.
- Pilot holes are drilled that will help guide the drilling rig.
- Trucks bring in the drilling rig and it is constructed on site. Once the rig is operating work continues 24 hours a day for three to four weeks.
- A vertical bore is drilled. The drill bits used to create this bore start out large and becoming increasingly smaller.
- As the well is being drilled a series of nested steel casings are put into place. These casings protect the well and water from contaminating each other. The first part of the well is drilled 50-80 feet wide and protected with conductor casing.
- These casings always extend passed the freshwater zone, which is typically up to 800 feet under the earth's surface. Some states set predetermined depths for casings.
- As wells are being drilled, the rocks, dirt and other debris are brought up to the earth's surface. Typically, there are laws dictating how to dispose of this debris.
- Once sufficient surface and conductor casing has been installed operators install a blowout preventer. Some operators may install a series of high pressure valves and seals that also help control the pressure in the well and prevent leaks to the surface.
- After measures have been taken to prevent blowouts, operators drill passed the installed casing, which is below water wells, to a few hundred feet above the desired shale formation. During this phase drilling mud is used to keep the drill bit cool. Drilling mud is a combination of bentonite clay and other thickeners.
- A new drill bit is then used that will allow the drill to move horizontally, once the drill has reached the "kick off point."
- This new drill is lowered until it reaches the kick off point where it then moves horizontally.
- Then more casing is installed along the full length of the well.
- Cement is then pumped into the well to hold the casing in place. This cement is tailored to meet the needs of each different shale formation.
- Before any oil or gas can be extracted a series of pressure tests are completed to check the integrity of the well.
The entire fracturing process takes from two days to one week.
- A fracturing crew is brought in, along with high pressure pumps and blending equipment.
- Water, which is stored on site, is pumped into a hydration unit where it is gelled.
- This water is then mixed with proppants and chemicals that are targeted to meet the needs of each formation and well. Most of the creation of this frac fluid is done by a team from a fluid monitoring van.
- A perforating tool is temporality lowered into the well. The perforating tool shoots small holes in the casing and cement creating a conduit between the wellbore and the oil or gas resources.
- Frac fluid is then pumped down into the well. The sand or proppant in this fluid remains behind to hold the fractures open as the water used during this process returns to the surface.
- Bridge plugs, the plugs that allow parts of the well to be isolated from one another, are inserted. The fracturing crew then repeats the above steps across the entire well until all the fractures have been completed. A typical well goes through 10 to 30 stages of this fracturing.
- The bridge plugs are then removed and oil and gas flows to the surface of the well.
- Once the fracking process is complete produced water can be released.
Well site reclamation
- Once the well has been exhausted site reclamation begins. Most states have rules dictating what is required in that state to reclaim an oil or gas well site.
- Reclamation includes closing the well, removing all storage tanks, vehicles and other equipment, returning the land to its previous form by shaping it and planting seeds.
Ballot measures about fracking
- See also: Notable 2014 local measures
- City of Denton Fracking Ban Initiative (2014)
- City of Athens Fracking Ban Proposal Initiative (November 2014)
- City of Niles "Community Bill of Rights" Fracking Ban Initiative (November 2014)
- Butte County Fracking Ban Initiative (November 2014)
- Santa Barbara County Fracking Ban Initiative (November 2014)
- San Benito County Fracking Ban Initiative (November 2014)
- Mendocino County Community Bill of Rights Fracking and Water Use Initiative (November 2014)
City of Loveland Two Year Fracking Suspension Initiative, Question 1 (June 2014)
Youngstown "Community Bill of Rights" Fracking Ban Charter Amendment (May 2014)
Johnson County Fracking Ban Referendum (March 2014)
- The Dangers of Fracking website
- Is Fracking Safe? The Top 10 Controversial Claims About Natural Gas Drilling
- Frac Focus chemical disclosure website
- U.S. Energy Information Administration, “Energy in Brief,” accessed January 28, 2014
- Frack Wire, “What is Fracking,” accessed January 28, 2014
- Bob Puls, University of Oklahoma, "Hydraulic Fracturing and Water Resources," accessed March 12, 2014
- American Oil and Gas History, "Shooters – A “Fracking” History," April 20, 2013
- The website called Frac Focus lists the chemicals reportedly used in the hydraulic fracturing process. Those who defend fracking argue that none of them are toxic or particularly dangerous in any way.
- Frac Focus chemical disclosure website
- More information on permitting is available on each state's fracking page, see for example Fracking in Illinois.