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Fracking in the United States

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Hydraulic fracturing (called "frac jobs"[1] or "frac'ing" in the industry,[2] with the spelling "fracking" being common in media reports[3]) is a process that results in the creation of fractures in rocks. The fracturing is done from a wellbore drilled into reservoir rock formations to increase the rate and ultimate recovery of oil and natural gas.

Hydraulic fractures may be natural or man-made and are extended by internal fluid pressure which opens the fracture and causes it to extend through the rock. Natural hydraulic fractures include volcanic dikes, sills and fracturing by ice as in frost weathering. Man-made fluid-driven fractures are formed at depth in a borehole and extend into targeted formations. The fracture width is typically maintained after the injection by introducing a proppant into the injected fluid. Proppant is a material, such as grains of sand, ceramic, or other particulates, that prevent the fractures from closing when the injection is stopped.

Considerable controversy surrounds the current implementation of hydraulic fracturing technology in the United States. Environmental safety and health concerns have emerged and are being debated at the state and national levels.[4][5][6]

Purpose

The technique of hydraulic fracturing is used to increase or restore the rate at which fluids, such as oil, gas or water, can be produced from a reservoir, including unconventional reservoirs such as shale rock or coal beds. Hydraulic fracturing enables the production of natural gas and oil from rock formations deep below the earth's surface (generally 5,000-20,000 feet or 1,500-6,100 m). At such depth, there may not be sufficient porosity and permeability to allow natural gas and oil to flow from the rock into the wellbore at economic rates. For example, creating conductive fractures in the rock is essential to produce gas from shale reservoirs because of the extremely low natural permeability of shale, (which is measured in the microdarcy to nanodarcy range). The fracture provides a conductive path connecting a larger area of the reservoir to the well, thereby increasing the area from which natural gas and liquids can be recovered from the targeted formation.

While the main industrial use of hydraulic fracturing is in stimulating production from oil and gas wells,[7][8][9] hydraulic fracturing is also applied to:

  • Stimulating groundwater wells[10]
  • Preconditioning rock for caving or inducing rock to cave in mining[11]
  • As a means of enhancing waste remediation processes (usually hydrocarbon waste or spills) or spills.[12]
  • Dispose of waste by injection into suitable deep rock formations
  • As a method to measure the stress in the earth.

History

Hydraulic fracturing for stimulation of oil and natural gas wells was first used in the United States in 1947.[13][14] It was first used commercially by Halliburton in 1949,[13] and because of its success in increasing production from oil wells was quickly adopted, and is now used worldwide in tens of thousands of oil and natural gas wells annually. The first industrial use of hydraulic fracturing was as early as 1903, according to T.L. Watson.[15] Before that date, hydraulic fracturing was used at Mt. Airy Quarry, near Mt Airy, North Carolina where it was (and still is) used to separate granite blocks from bedrock.

Volcanic dikes and sills are examples of natural hydraulic fractures. Hydraulic fracturing incorporates results from the disciplines of fracture mechanics, fluid mechanics, solid mechanics, and porous medium flow.

Method

A hydraulic fracture is formed by pumping the fracturing fluid into the wellbore at a rate sufficient to increase the pressure downhole to a value in excess of the fracture gradient of the formation rock. The pressure causes the formation to crack, allowing the fracturing fluid to enter and extend the crack farther into the formation. To keep this fracture open after the injection stops, a solid proppant, commonly a sieved round sand, is added to the fracture fluid. The propped hydraulic fracture then becomes a high permeability conduit through which the formation fluids can flow to the well.

There are two different types of Hydraulic Fracturing (conventional and unconventional) that use similar techniques to extract gas from shale rock. Conventional fracturing consists of drilling a vertical borehole or well 8,000 feet into the earth. Unconventional fracturing consists of drilling a vertical borehole or well 8,000 feet into the earth and then turning the drill-bit horizontally to maximize gas recovery from one bore site. They both involve applying downward pressure to a rotating drill bit. This drilling action produces rock chips and fine rock particles that may enter cracks and pore space at the wellbore wall, resulting in damage to the permeability at and near the wellbore. The damage reduces flow into the borehole from the surrounding rock formation, and partially seals off the borehole from the surrounding rock. Hydraulic fracturing can be used to mitigate this damage.

Hydraulic fracture stimulation is commonly applied to wells drilled in low permeability reservoirs. An estimated 90 percent of the natural gas wells in the United States use hydraulic fracturing to produce gas at economic rates.

The fracture fluid can be any number of fluids, ranging from water to gels, foams, nitrogen, carbon dioxide or air in some cases. Various types of proppant are used, including sand, resin-coated sand, and man-made ceramics depending on the type of permeability or grain strength needed. Radioactive sand is sometimes used so that the fracture trace along the wellbore can be measured. The injected fluid mixture is approximately 99 percent water and sand.

Microseismic monitoring is a common method for measuring the orientation and approximate size of a hydraulic fracture. Microseismic activity is measured by placing an array of geophones in a nearby wellbore. By mapping the location of small seismic events that are associated with the growing hydraulic fracture, the approximate geometry of the fracture is inferred. Tiltmeter arrays, deployed on the surface or down a well, provide another technology for monitoring the fracture geometry.

Hydraulic fracturing equipment used in oil and natural gas fields usually consists of a slurry blender, one or more high pressure, high volume fracturing pumps (typically powerful triplex, or quintiplex pumps) and a monitoring unit. Associated equipment includes fracturing tanks, high pressure treating iron, a chemical additive unit (used to accurately monitor chemical addition) low pressure pipes and gauges for flow rate, fluid density, and treating pressure. Fracturing equipment operates over a range of pressures and injection rates, and can reach up to 100 MPa (15,000 psi) and 265 L/s (100 barrels per minute).

The location of fracturing along the length of the borehole can be controlled by inserting composite plugs, also known as bridge plugs, below and above the region to be fractured.[16] This allows a borehole to be progressively fractured along the length of the bore, without leaking fracture fluid out through previously fractured regions. Piping through the upper plug admits fracturing fluid and proppant into the working region. This method is commonly referred to as "plug and perf."

Typically, hydraulic fractures are placed in cased wellbores and the reservoir zones to be fractured are accessed by perforating the casing at those locations.

Advances in completion technology have led to the emergence of open hole multi-stage fracturing systems. These systems effectively place fractures in specific places in the wellbore, thus increasing the cumulative production in a shorter time frame.[17]

Certain reservoirs such as the Bakken, Barnett Shale, Montney and Haynesville Shale have proved to be difficult to produce using conventional methods. These formations have begun using high tech completion systems capable of mechanically fracturing at certain intervals. An alternative to the plug and perf method, multi-stage fracturing systems are capable of stimulating several stages in a single day. Compared to the weeks required by the plug and perf method, cost-effective multi-stage completion systems are quickly becoming sought after technology by oil and natural gas companies.[18]

Environmental and health effects

Some environmental and human health concerns possibly associated with hydraulic fracturing include the contamination of ground water, risks to air quality, the migration of gases and hydraulic fracturing chemicals to the surface, and the potential mishandling of waste. The potential costs associated with possible environmental clean-up processes, loss of land value and human and animal health concerns are undetermined. New technological advances and appropriate state regulations are working to study and safely implement the process.

A number of chemicals identified in fracturing fluid are hazardous chemicals that may cause health risks that range from rashes to cancer. Some civilians that ingest these chemicals complain about symptoms of rashes and sores. Some chemicals are identified as carcinogens. Some chemicals found injected into the earth identify as endocrine disruptors, which interrupts hormones and glands in the body that control development, growth, reproduction and behavior in animals and humans.

Hydraulic fracturing has a significant environmental impact, with arguments centered around the extent to which fracturing fluid used far below the earth's surface and will pollute fresh water zones, will contaminate surface or near-surface water supplies, impact rock shelf causing seismic events or lead to surface subsidence. However, well casing failures and failures of the gas well grouting systems may have been responsible for gas migration into drinking water aquifers in Dimock, Pennsylvania. Also, water-related pollution events that occur from hydraulic fracturing are on or relatively near the surface. With the transport, handling, storage and use of chemicals and chemical-laden water, accidents that release materials into the environment may occur.

In April 2010 the state of Pennsylvania banned Cabot Oil & Gas Corp. from further drilling in the entire state until it plugs wells believed to be the source of contamination of the drinking water of 14 homes in Dimock Township, Pennsylvania. The investigation was initiated after a water well exploded on New Year's Day in 2009. The state investigation revealed that Cabot Oil & Gas Company "had allowed combustible gas to escape into the region's groundwater supplies."[19]

A well blowout in Clearfield County, Pennsylvania on June 3, 2010 sent more than 35,000 gallons of hydraulic fracturing fluids into the air and onto the surrounding landscape in a forested area. Campers were evacuated and the company EOG Resources and the well completion company C.C. Forbes have been ordered to cease all operations in the state of Pennsylvania pending investigation. The Pennsylvania Department of Environmental Protection has called this a "serious incident".[20][21]

Injection of fluid into subsurface geological structures, such as faults and fractures, reduces the effective normal stress acting across these structures. If sufficient shear stress is present, the structure may slip in shear and generate seismic events over a range of magnitudes. Subsidence is not directly caused by hydraulic fracturing but may occur after considerable production of oil or ground water. Subsidence occurs over reservoirs whether they have been subject to hydraulic fracturing or not because it is a result of producing fluids from the reservoir and lowering the reservoir pore pressure. The subsidence process can be associated with some seismicity. Reports of minor tremors of no greater than 2.8 on the Richter scale were reported on June 2, 2009 in Cleburne, Texas, the first in the town's 140-year history.[22]

One use of hydraulic fracturing is in stimulating water wells. In that case, the fluid used may be pure water (typically water and a disinfectant such as bleach).[citation needed] Another use of hydraulic fracturing is to remediate waste spills by injecting bacteria, air, or other materials into a subsurface contaminated zone.[citation needed]

It has been reported that the hydraulic fracturing industry has refused to publicly disclose, due to intellectual property concerns, the specific formulation of the fluids employed in the fracturing process. A "NOW on PBS" episode aired in March 2010 introduces the documentary film Gasland. The filmmaker claims that the chemicals include toxins, known carcinogens and heavy metals which may have polluted the ground water near well sites in Pennsylvania and Colorado. The film also makes a case for explosive gases entering private potable water wells, causing "flammable water".

Energy in Depth, an oil and gas industry organization has published a list of chemicals in a "typical solution used in hydraulic fracturing," but notes "The specific compounds used in a given fracturing operation will vary."[23]

The New York State Department of Environmental Conservation has published a list of chemicals used in fracturing fluids.

A 2008 newspaper report states that medical personnel were inhibited in their treatment of workers injured in a fracturing accident because they did not know which specific chemicals were used. In the article, a nurse claimed she may have been exposed to the unknown chemicals on the patient's clothes.[24] Release of information, pertaining to hazardous components of any and all industrial chemicals, to medical and emergency personnel has been governed by OSHA since the 1974 Right-To-know legislation.

In the United States, a 2004 Environmental Protection Agency (EPA) study concluded that the process was safe and didn't warrant further study, because there was "no unequivocal evidence" of health risks, and the fluids were neither necessarily hazardous nor able to travel far underground. That study, however, was not intended as a general study of hydraulic fracturing, but only of its use in coalbed methane deposits, and the study did not consider impacts above ground.[25] The EPA report did find uncertainties in knowledge of how fracturing fluid migrates through rocks, and upon its release service companies voluntarily agreed to stop using diesel fuel as a component of fracturing fluid in coalbed methane walls due to public concerns of its potential as a source of benzene contamination.[26]

With critics claiming that Bush administration officials influenced the 2004 EPA study, the U.S. Congress has requested that the EPA undertake a new, broader study of hydraulic fracturing. The report is due to be released in 2012.[27]

The increased use of hydraulic fracturing has prompted more speculation about its environmental dangers. A 2008 investigation of benzene contamination in Colorado and Wyoming led some EPA officials to suggest hydraulic fracturing as a culprit. One of the authors of the 2004 EPA report states that it has been misconstrued by the gas-drilling industry.[25]

A typical frac will utilize approximately 15,000 m3 of water per well. Currently, the number of fractures per well is increasing. At this time, there has been no investigation into the unregulated pollution of fresh water by the Canadian Government.

One hazard that is commonly overlooked is the venting of bulk sand silos directly to atmosphere. When they are being filled, or emptied during the fracture a fine cloud of silica particulate will be venting directly to atmosphere. This dust has the potential to travel many kilometers on the wind directly into populated areas. While the immediate personnel are wearing personal protective equipment, families in the area of a well fracture can potentially be exposed. However, sand used for proppant is washed to remove fines and is, therefore, virtually dust free.

Regulation

The Energy Policy Act of 2005 exempted wells which are hydraulic fractured from being re-classified as injection wells, placing them under federal regulation under the Safe Drinking Water Act.[25] which was originally intended to regulate disposal wells. Reports of ground water contamination have questioned whether the exemption is appropriate. A complete listing of the specific chemical formulation of additives used in hydraulic fracturing operations are not currently made available to landowners, neighbors, local officials, or health care providers. This practice is under scrutiny as well.

Two studies released in 2009, one by the U.S. Department of Energy and the other released by the Ground Water Protection Council, address hydraulic fracturing safety concerns. The industry contends that the chemicals in use have been adequately disclosed through Material Safety Data Sheets (MSDS) available on the OSHA website and that additional regulation is burdensome.[28] Chemicals which can be used in the fracturing fluid include kerosene, benzene, toluene, xylene, and formaldehyde.[29] It must be noted that these chemicals are not directly used as treating chemical additives but can be a small component of the specific chemicals used in the job.[29]

On June 8, 2010 the Wyoming Oil and Gas Conservation Commission voted to require full disclosure of the hydraulic fracturing fluids used in natural gas exploration.[30] This may aid in tracking pollutants that have migrated from hydraulically fractured gas wells.[31]

Congress has been urged to repeal the 2005 regulatory exemption under the Energy Policy Act of 2005.[32] The FRAC Act, introduced in June 2009, would eliminate the exemption and might allow producing wells to be reclassified as injection wells placing them under federal jurisdiction in states without approved UIC programs.

On November 30th, the New York State assembly voted 93 to 43 to place a moratorium or freeze on hydraulic fracturing to give the state more time to undertake safety and environmental concerns.[33]

The U.S. FRAC Act of 2009

In June 2009 two identical bills named the FRAC Act were introduced to both the United States House and the Senate. FRAC stands for Fracturing Responsibility and Awareness of Chemicals Act. The House bill was introduced to the Senate by Diana Degette, Jared Polis, and Maurice Hinchey. Bob Casey and Chuck Schumer.[34] These bills are designed to amend the Safe Drinking Water Act. This would allow the Environmental Protection Agency to regulate hydraulic fracturing that occurs in states which have not taken primacy in UIC regulation. The bill also requires the energy industry to reveal what chemicals are being used in the sand-water mixture.

However, the policy calls only for the "chemical constituents (but not the proprietary chemical formulas) used in the fracturing process." Once these constituents are determined the information must be revealed to the public through the Internet. The firms that use the fracturing process have refused to disclose this information because they claim it is a trade secret. The FRAC Act states that in any case where a physician or the State finds that a medical emergency exists, and that the chemical formulas are needed to treat the ailing individual, the firm must disclose the chemical identity to the State or physician - even if that proprietary formula is a trade-secret chemical. Material Safety Data Sheets, required by OSHA under 29 CFR 1910.1200[35] are developed and made available to first responders and other emergency planning and response officials.

ProPublica, an online journal, has published a number of reports that suggest hydraulic fracturing could be the cause of water contamination in areas surrounding drilling operations. However, the Environmental Protection Agency says that they have not been able to conclude whether fracturing is the cause of this contamination. At the same time, numerous state regulatory officials have recently confirmed that they are not aware of any confirmed instances of contamination of drinking water sources due to hydraulic fracturing in their states. The agency blames this lack of information on the 2005 Energy Policy Act because it exempts hydraulic fracturing from federal water laws.[36] The writers of the FRAC Act claim that they are attempting to protect the people who live in close proximity to fracturing from potentially dangerous chemicals leaching into ground water resources. The energy industry does not agree with this pending policy. They see it as "an additional layer of regulation that is unneeded and cumbersome."[37] The Independent Petroleum Association of America believes that states already sufficiently regulate hydraulic fracturing. Their research suggests that federal regulation could result in the addition of about $100,000 to each new natural gas well.[34] Energy in Depth, a lobbying group, says the new regulation would be an "unnecessary financial burden on a single small-business industry, American oil, and natural gas producers." This group also claims that the FRAC Act could result in half of the United States oil wells and one third of the gas wells being closed. Also, the bill could cause domestic gas production to drop by 245 billion cubic feet per year along with four billion dollars in lost revenue to the federal government.[38] The Environmental Protection Agency claims that the section that would be amended in the Safe Drinking Water Act is flexible in that it defers regulation of fracturing and drilling to the state. The EPA also says that since most states currently have regulations on fracturing, they would most likely agree with the state's policy and there would not be much change.[34] The FRAC Act has been heard in both the House and the Senate. It has been referred to the Committee on Environment and Public Works, where it remains to this day. Congresswoman Diana DeGette says that she is still deciding if the bill is to proceed alone or if it will be attached to a larger piece of legislation.

Driving forces

Fracturing may be done by pumping in liquids at high pressure, using combustible gas mixtures alone or driving liquids, or using explosives to generate high-pressure high-speed gas flow (TNT or PETN up to 1,900,000 psi). In the late 1960s and early 1970s, as part of Operation Plowshare, underground nuclear explosions were tested for natural gas stimulation. The Rulison explosion multiplied the accessibility of the gas, but the gas was contaminated and unmarketable.

Identified by the state of New York as being "Chemical Constituents in Additives/Chemicals" used in Fracturing

(Extracted from http://www.dec.ny.gov/docs/materials_minerals_pdf/ogdsgeischap5.pdf)

CAS Number Chemical Constituent
2634-33-5 1,2 Benzisothiazolin-2-one / 1,2-benzisothiazolin-3-one
95-63-6 1,2,4 trimethylbenzene
123-91-1 1,4-Dioxane
3452-07-1 1-eicosene
629-73-2 1-hexadecene
112-88-9 1-octadecene
1120-36-1 1-tetradecene
10222-01-2 2,2 Dibromo-3-nitrilopropionamide , a biocide
27776-21-2 2,2'-azobis-{2-(imidazlin-2-yl)propane}-dihydrochloride
73003-80-2 2,2-Dobromomalonamide
15214-89-8 2-Acrylamido-2-methylpropane sulphonic acid sodium salt polymer
46830-22-2 2-acryloyloxyethyl(benzyl)dimethylammonium chloride
52-51-7 2-Bromo-2-nitro-1,3-propanediol
111-76-2 2-Butoxy ethanol
1113-55-9 2-Dibromo-3-Nitriloprionamide (2-Monobromo-3-nitriilopropionamide)
104-76-7 2-Ethyl Hexanol
67-63-0 2-Propanol / Isopropyl Alcohol / Isopropanol / Propan-2-ol
26062-79-3 2-Propen-1-aminium, N,N-dimethyl-N-2-propenyl-chloride, homopolymer
9003-03-6 2-propenoic acid, homopolymer, ammonium salt
25987-30-8 2-Propenoic acid, polymer with 2 p-propenamide, sodium salt / Copolymer of acrylamide and sodium acrylate
71050-62-9 2-Propenoic acid, polymer with sodium phosphinate (1:1)
66019-18-9 2-propenoic acid, telomer with sodium hydrogen sulfite
107-19-7 2-Propyn-1-ol / Propargyl alcohol
51229-78-8 3,5,7-Triaza-1-azoniatricyclo[3.3.1.13,7]decane, 1-(3-chloro-2-propenyl)-chloride,
115-19-5 3-methyl-1-butyn-3-ol
127087-87-0 4-Nonylphenol Polyethylene Glycol Ether Branched / Nonylphenol ethoxylated / Oxyalkylated Phenol
64-19-7 Acetic acid
68442-62-6 Acetic acid, hydroxy-, reaction products with triethanolamine
108-24-7 Acetic Anhydride
67-64-1 Acetone
79-06-1 Acrylamide

Terminology

Fracture Gradient
The pressure to fracture the formation at a particular depth divided by the depth. A fracture gradient of 18 kPa/m (0.8 psi/foot) implies that at a depth of 3 km (10,000 feet) a pressure of 54 MPa (8,000 psi) will extend a hydraulic fracture.
ISIP - Instantaneous Shut In Pressure
The pressure measured immediately after injection stops. The ISIP provides a measure of the pressure in the fracture at the wellbore by removing contributions from fluid friction.
Leakoff
Loss of fracturing fluid from the fracture channel into the surrounding permeable rock.
Fracturing fluid
The fluid used during a hydraulic fracture treatment of oil, gas or water wells. The fracturing fluid has two major functions 1) Open and extend the fracture; 2) Transport the proppant along the fracture length.
Proppant
Suspended particles in the fracturing fluid that are used to hold fractures open after a hydraulic fracturing treatment, thus producing a conductive pathway that fluids can easily flow along. Naturally occurring sand grains or artificial ceramic material are common proppants used.
Concise slang
"Fracing" (sometimes spelled "fracking"[39]) is a shortened version of fracturing.

References

  1. ^ glossary.oilfield.slb.com Schlumberger Oilfield Glossary
  2. ^ stocks.investopedia.com/stock-analysis/2010/Will-The-EPA-Crack-Down-On-Fracking
  3. ^ [1]
  4. ^ Fox, Josh (June 18, 2010). "New Film Investigates 'Fracking' For Natural Gas" (Interview). Interviewed by Ira Flatow. Retrieved June 21, 2010. {{cite interview}}: Unknown parameter |callsign= ignored (help); Unknown parameter |city= ignored (|location= suggested) (help); Unknown parameter |program= ignored (help)
  5. ^ Margot Roosevelt (June 18, 2010). "Gulf oil spill worsens -- but what about the safety of gas fracking?". LA Times. Retrieved June 21, 2010.
  6. ^ "EPA Announces a Schedule of Public Meetings on Hydraulic Fracturing Research Study". United States Environmental Protection Agency. June 21, 2010. Retrieved June 21, 2010.
  7. ^ Gidley, J.L. et al. (editors), Recent Advances in Hydraulic Fracturing, SPE Monograph, SPE, Richardson, Texas, 1989.
  8. ^ Yew, C.H., Mechanics of Hydraulic Fracturing, Gulf Publishing Company, Houston, Texas, 1997.
  9. ^ Economides, M.J. and K.G. Nolte (editors), Reservoir Stimulation, John Wiley & Sons, Ltd., New York, 2000.
  10. ^ Banks, David (1996). "Permeability and stress in crystalline rocks". Terra Nova. 8 (3): 223–235. doi:10.1111/j.1365-3121.1996.tb00751.x. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  11. ^ Brown, E.T., Block Caving Geomechanics, JKMRC Monograph 3, JKMRC, Indooroopilly, Queensland, 2003.
  12. ^ U. Frank, N. Barkley, Remediation of low permeability subsurface formations by fracturing enhancement of soil vapor extraction, Journal of Hazardous Materials, Volume 40, Issue 2, Soil Remediation: Application of Innovative and Standard Technologies, February 1995, Pages 191-201, ISSN 0304-3894, DOI: 10.1016/0304-3894(94)00069-S.
  13. ^ a b Howard, G.C. and C.R. Fast (editors), Hydraulic Fracturing, Monograph Vol. 2 of the Henry L. Doherty Series, Society of Petroleum Engineers New York, 1970.
  14. ^ Montgomery, Carl T. (2010). "Hydraulic Fracturing: History of an Enduring Technology" (PDF). Journal of Petroleum Technology. 62 (12). Society of Petroleum Engineers: 26–32. ISSN 0149-2136. Retrieved January 5, 2011. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  15. ^ Watson, T.L., Granites of the southeastern Atlantic states, U.S. Geological Survey Bulletin 426, 1910.
  16. ^ http://oilgasglossary.com/bridge-plug.html
  17. ^ Rocky Seale, Open hole completion systems enables multi-stage fracturing and stimulation along horizontal wellbores. Fracturing stimulation. Retrieved Oct,1 2009
  18. ^ Shaun Polczer. 2009-07-25. Packers Plus leads drilling revolution. Calgary Herald.
  19. ^ Michael Rubinkam, Pa. regulators shut down Cabot drilling, April 15, 2010, pressconnects.com
  20. ^ Gas eruption fallout, The River Reporter, June 10-16, 2010
  21. ^ Anya Litvak, Marcellus Shale well blowout prompts second DEP suspension, Pittsburgh business Times, June 9, 2010.
  22. ^ "Drilling Might Be Culprit Behind Texas Earthquakes". Associated Press. June v12, 2009. {{cite news}}: Check date values in: |date= (help)
  23. ^ Energy in Depth, A Fluid Situation: Typical Solution Used In Hydraulic Fracturing, July 20, 2008, The Durango Herald
  24. ^ Joe Hanel, Secrets surround gas-field chemicals, July 20, 2008, The Durango Herald
  25. ^ a b c An example of the composition of a typical fracturing fluid can be found in Typical Solution Used in Hydraulic Fracturing, energyindepth.org. A more complete listing of chemicals used in fracturing fluid, which includes kerosene, benzene, tolulene, xylene, formaldehyde to name a few, may be found in Chapter 5 Natural Gas Development Activities And High‐Volume Hydraulic Fracturing.[clarification needed] Cite error: The named reference "businessweek" was defined multiple times with different content (see the help page).
  26. ^ http://www.epa.gov/ogwdw/uic/pdfs/cbmstudy_attach_uic_final_fact_sheet.pdf
  27. ^ Burdeau, Cain. "EPA to Study 'Fracking' Gas Drilling Method." Associated Press. 18 March 2010. http://abcnews.go.com/Business/wireStory?id=10141059
  28. ^ hydraulicfracturing.com.
  29. ^ a b Chapter 5 Natural Gas Development Activities And High‐Volume Hydraulic Fracturing. Cite error: The named reference "chemicals" was defined multiple times with different content (see the help page).
  30. ^ David O. Williams, oil and gas regulators approve new rules for frack fluid disclosure, june 8, 2010, The Colorado Independent.
  31. ^ Wyoming approves 'fracking' disclosure rules , June 9, 2010, trib.com
  32. ^ Mulkern, Anne C. (May 7, 2009). "Industry campaign targets 'hydraulic fracturing' bill". The New York Times. Retrieved May 4, 2010.
  33. ^ Navarro, Mireya. "N.Y. Assembly Approves Fracking Moratorium". The New York Times Company.
  34. ^ a b c Lustgarten, Abraham. FRAC Act — Congress Introduces Twin Bills to Control Drilling and Protect Drinking Water. ProPublica. June 9, 2009.
  35. ^ Occupational Safety and Health Standards : Toxic and Hazardous Substances, OSHA.
  36. ^ Environmental Effects of Hydraulic Fracturing, Hunter Valley Protection Alliance, 2008.
  37. ^ Advanced Resources International. Potential Economic and Energy Supply Impacts of Proposals to Modify Federal Environmental Laws Applicable to the U.S. Oil and Gas Exploration and Production Industry. Prepared for U.S. Department of Energy. January, 2009.
  38. ^ Tronche, John Laurent. "U.S. Representatives Unveil FRAC Act to close 'Halliburton Loophole.'" Fort Worth Business Press. June 9, 2009. www.fwbusiness.com.
  39. ^ Ed Quillen, Fracking, fracing or fraccing?, June 25, 2009, High Country News.
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