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"Fracking" redirects here. For the expletive, see Frak (expletive).
Tower for drilling a well into the Marcellus Shale Formation for natural gas, Lycoming County, PA, USA 2009

Hydraulic fracturing is the propagation of fractures in a rock layer caused by the presence of a pressurized fluid. Hydraulic fractures form naturally, as in the case of veins or dikes, and is one means by which gas and petroleum from source rocks may migrate to reservoir rocks.

Energy companies may attempt to accelerate this process in order to release petroleum, natural gas, coal seam gas, or other substances for extraction, via a technique called induced hydraulic fracturing (illustration), often shortened to fracking[a] or hydrofracking.[1] This type of fracturing, known colloquially as a 'frac job',[2] creates fractures from a wellbore drilled into reservoir rock formations. A distinction can be made between low-volume hydraulic fracturing used to stimulate high-permeability reservoirs, which may consume typically 20,000 to 80,000 gallons of fluid per well, with high-volume hydraulic fracturing, used in the completion of tight gas and shale gas wells; high-volume hydraulic fracturing can use as much as two to three million gallons of fluid per well.[3] This latter practice has come under scrutiny internationally, with some countries suspending it, or even banning it completely. The first frac job was performed in 1947,[4] though the current fracking technique was first used in the late 1990s in the Barnett Shale in Texas.[5] The energy from the injection of a highly-pressurized fracking fluid creates new channels in the rock which can increase the extraction rates and ultimate recovery of fossil fuels.

Globally, the expectation that gas use will rise by more than 50% compared to 2010 levels, and account for over 25% of world energy demand in 2035 has led the International Energy Agency in 2011 to herald a "golden age of gas".[6] Proponents of fracking point to the vast amounts of formerly inaccessible hydrocarbons the process can extract. However, there remain large uncertainties in the amount of gas reserves that can be accessed in this way.[7]Some have said that hydraulic fracturing would give the United States energy independence,[8] but others disagree.[9] Oil and gas companies have sought and received permission from the US Department of Energy (DOE)[10] to export oil and gas to Europe and Asia (e.g., China and Korea)[9] via new pipelines[11][12] to export terminals[13][14] on the Gulf Coast and East Coast.[15][10] Higher prices abroad have also led to acquisition of US natural gas companies[16] and shares of companies and their shale plays by Chinese, Japanese, and French companies[17][18]

There are environmental concerns regarding the contamination of ground water, risks to air quality, the migration of gases and hydraulic fracturing chemicals to the surface,[19] Complaints from a few residents on water quality in a developed natural gas field prompted an EPA groundwater investigation in Wyoming. The EPA reported detections of methane and other chemicals such as phthalates in private water wells.[20] and the health effects of these.[21][22][23][24][25][26] Lower gas prices have also reduced the incentive to investigate renewable sources of energy, perpetuating dependence on gas and oil.[27]

History

The first frac job was performed in 1947,[28] in limestone deposits.

Significant R&D and technology demonstration were necessary before hydraulic fracturing could be commercially applied to shale gas deposits, due to shale's high porosity and low permeability.[29] In the 1970s the federal government initiated both the Eastern Gas Shales Project, a set of dozens of public-private hydro-fracturing pilot demonstration projects, and the Gas Research Institute,[30] a gas industry research consortium that received approval for research and funding from the Federal Energy Regulatory Commission. Over this time, Sandia National Laboratories was conducting research into microseismic imaging for use in coalbeds, a geologic mapping technique that would prove crucial for the commercial recovery of natural gas from shale as well as oil from offshore drilling rigs. In the late 1970s, the Department of Energy pioneered massive hydraulic fracturing (MHF), a drilling technique that would be improved upon for the economic recovery of shale gas in the future. In 1986, a joint DOE-private venture completed the first successful multi-fracture horizontal well in shale. The Department of Energy later subsidized Mitchell Energy's first successful horizontal drill in the north-Texas Barnett Shale in 1991.[31] Mitchell Energy engineers would go on to develop the hydraulic fracturing technique known as 'slickwater fracturing' that started the modern shale gas boom.[32]

Mechanics

Fracturing in rocks at depth is suppressed by the confining pressure, due to the load caused by the overlying rock strata. This is particularly so in the case of 'tensile' (Mode 1) fractures, which require the walls of the fracture to move apart, working against this confining pressure. Hydraulic fracturing occurs when the effective stress is reduced sufficiently by an increase in the pressure of fluids within the rock, such that the minimum principal stress becomes tensile and exceeds the tensile strength of the material.[33][34] Fractures formed in this way will typically be oriented perpendicularly to the minimum principal stress and for this reason, induced hydraulic fractures in wellbores are sometimes used to determine stress orientations.[35] In natural examples, such as dikes or vein-filled fractures, their orientations can be used to infer past stress states.[36]

Natural examples

Rocks often contain evidence of past hydraulic fracturing events.

Veins

Most vein systems are a result of repeated hydraulic fracturing during periods of relatively high pore fluid pressure. This is particularly clear in the case of 'crack-seal' veins, where the vein material can be seen to have been added in a series of discrete fracturing events, with extra vein material deposited on each occasion.[37] One mechanism to explain such examples of long-lasting repeated fracturing, is the effects of seismic activity, in which the stress levels rise and fall episodically and large volumes of fluid may be expelled from fluid-filled fractures during earthquakes, a process referred to as 'seismic pumping'.[38]

Dikes

High-level minor intrusions such as dikes propagate through the crust in the form of fluid-filled cracks, although in this case the fluid is magma. In sedimentary rocks with a significant water content the fluid at the propagating fracture tip will be steam.[39]

Induced hydraulic fracturing

The technique of hydraulic fracturing is used to increase or restore the rate at which fluids, such as oil, water, or natural gas can be produced from subterranean natural reservoirs. Reservoirs are typically porous sandstones, limestones or dolomite rocks, but also include '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, permeability or reservoir pressure to allow natural gas and oil to flow from the rock into the wellbore at economic rates. Thus, creating conductive fractures in the rock is essential to extract gas from shale reservoirs because of the extremely low natural permeability of shale, which is measured in the microdarcy to nanodarcy range.[40] Fractures provide 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. So-called 'super fracking', which creates deeper cracks to release more oil and gas, will allow companies to frack more efficiently.[41] The yield for a typical shale gas well generally falls off sharply after the first year or two.[42]

While the main industrial use of hydraulic fracturing is in stimulating production from oil and gas wells,[43][44][45] hydraulic fracturing is also applied to:

  • Stimulating groundwater wells[46]
  • Preconditioning rock for caving or inducing rock to cave in mining[47]
  • As a means of enhancing waste remediation processes, usually hydrocarbon waste or spills[48]
  • Dispose of waste by injection into deep rock formations
  • As a method to measure the stress in the earth
  • For heat extraction to produce electricity in an enhanced geothermal systems [49]

Method

A hydraulic fracture is formed by pumping the fracturing fluid into the wellbore at a rate sufficient to increase pressure downhole to exceed that of the fracture gradient of the rock. [citation needed] The rock cracks and the fracture fluid continues farther into the rock, extending the crack still farther, and so on. Operators typically try to maintain "fracture width", or slow its decline, following treatment by introducing a proppant into the injected fluid, a material, such as grains of sand, ceramic, or other particulates, that prevent the fractures from closing when the injection is stopped. Consideration of proppant strengths and prevention of proppant failure becomes more important at deeper depths where pressure and stresses on fractures are higher. The propped fracture is permeable enough to allow the flow of formation fluids to the well. Formation fluids include gas, oil, salt water, fresh water and fluids introduced to the formation during completion of the well during fracturing. [citation needed]

The location of one or more fractures along the length of the borehole is strictly controlled by various different methods which create or seal-off holes in the side of the wellbore. Typically, hydraulic fracturing is performed in cased wellbores and the zones to be fractured are accessed by perforating the casing at those locations. [citation needed]

Well types

While hydraulic fracturing is many times performed in vertical wells, today it is also performed in horizontal wells. When done in already highly-permeable reservoirs such as sandstone-based wells, the technique is known as "well stimulation".

Horizontal drilling involves wellbores where the terminal drillhole is completed as a 'lateral' that extends parallel with the rock layer containing the substance to be extracted. For example, laterals extend 1,500 to 5,000 feet in the Barnett Shale basin in Texas, and up to 10,000 feet in the Bakken formation in North Dakota. In contrast, a vertical well only accesses the thickness of the rock layer, typically 50–300 feet. Horizontal drilling also reduces surface disruptions as fewer wells are required. Drilling usually induces damage to the pore space at the wellbore wall, reducing the permeability at and near the wellbore. This 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 restore permeability. [citation needed]

Hydraulic fracturing is commonly applied to wells drilled in low permeability reservoir rock.

Fracturing

The fluid injected into the rock is typically a slurry of water, proppants, and chemical additives. Additionally, gels, foams, and compressed gases, including nitrogen, carbon dioxide and air can be injected. Various types of proppant include silica sand, resin-coated sand, and man-made ceramics. These vary depending on the type of permeability or grain strength needed. Sand containing naturally radioactive minerals is sometimes used so that the fracture trace along the wellbore can be measured. Chemical additives are applied to tailor the injected material to the specific geological situation, protect the well, and improve its operation, though the injected fluid is approximately 98-99.5% percent water,[50] varying slightly based on the type of well. The composition of injected fluid is sometimes changed as the fracturing job proceeds. Often, acid is initially used to scour the perforations and clean up the near-wellbore area. Afterward, high pressure fracture fluid is injected into the wellbore, with the pressure above the fracture gradient of the rock. This fracture fluid contains water-soluble gelling agents (such as guar gum) which increase viscosity and efficiently deliver the proppant into the formation.[3] As the fracturing process proceeds, viscosity reducing agents such as oxidizers and enzyme breakers are sometimes then added to the fracturing fluid to deactivate the gelling agents and encourage flowback.[3] The proppant's purpose is primarily to provide a permeable and permanent filler to fill the void created during the fracturing process. At the end of the job the well is commonly flushed with water (sometimes blended with a friction reducing chemical) under pressure. Injected fluid is to some degree recovered and is managed by several methods, such as underground injection control, treatment and discharge, recycling, or temporary storage in pits or containers while new technology is being developed to better handle wastewater and improve reusability.[50] Although the concentrations of the chemical additives are very low, the recovered fluid may be harmful due in part to hydrocarbons picked up from the formation.

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, one or more units for storage and handling of proppant, high pressure treating iron, a chemical additive unit (used to accurately monitor chemical addition), low pressure flexible hoses, and many gauges and meters 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). [citation needed]

Fracture monitoring

Injection of radioactive tracers along with the other substances in hydraulic fracturing fluid is used to determine the injection profile and location of fractures created by hydraulic fracturing.[51] US Patent No. 5635712 (George L. Scott III, Halliburton Company, 03-June-1997) describes this process. The patent lists a large number of gamma-emitting tracer isotopes that can be used as radioactive tracer material, including Gold-198, Xenon-133, Iodine-131, Rubidium-86, Chromium-51, Iron-59, Antimony-124, Strontium-85, Cobalt-58, Iridium-192, Scandium-46, Zinc-65, Silver-110, Cobalt-57, Cobalt-60, and Krypton-85.[52] A 1983 patent, by Walter H. Fertl, for Dresser Industries (Dallas, Texas) also lists Iodine-131 as a potential tracer, along with Scandium-46, Zirconium-95, and Iridium-192.[53] A 1995 patent by George L. Scott III, this time for The Energex Company (patent no. US5441110), also lists Iodine-131 as a suitable gamma-emitting tracer isotope, along with Potassium-39 (activated to Potassium-40), Potassium-41 (activated to Potassium-42), Potassium-43, Scandium-45 (activated to Scandium-46), Scandium-47, Scandium-48, Iodine-127, Iodine-128, Iodine-129, Iodine-130, Antimony-121, Antimony-122, Antimony-123, Antimony-124, Antimony-125, Antimony-126, and Antimony-127.[54]

Measurements of the pressure and rate during the growth of a hydraulic fracture, as well as knowing the properties of the fluid and proppant being injected into the well provides the most common and simplest method of monitoring a hydraulic fracture treatment. This data, along with knowledge of the underground geology can be used to model information such as length, width and conductivity of a propped fracture. [citation needed]

For more advanced applications, Microseismic monitoring is sometimes used to estimate the size and orientation of hydraulically induced fractures. Microseismic activity is measured by placing an array of geophones in a nearby wellbore. By mapping the location of any small seismic events 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 strains produced by hydraulic fracturing. [citation needed]

Emission of gases displaced by hydraulic fracturing into the atmosphere may be detected via atmospheric gas monitoring, and can be quantified directly via the eddy covariance flux measurements. [citation needed]

Horizontal completions

Since the early 2000s, advances in drilling and completion technology has made drilling horizontal wellbores much more economical. Horizontal wellbores allow for far greater exposure to a formation than a conventional vertical wellbore. This is particularly useful in shale oil and gas formations which do not have sufficient permeability to produce economically with a vertical well. Such wells when drilled onshore are now usually hydraulically fractured many times, especially in North America. The type of wellbore completion used will affect how many times the formation is fractured, and at what locations along the horizontal section of the wellbore.[55]

In North America, tight reservoirs such as the Bakken, Barnett Shale, Montney, Haynesville Shale and most recently Marcellus Shale are drilled, completed and fractured using this method. The method by which the fractures are placed along the wellbore is most commonly achieved by one of two methods, known as 'plug and perf' and 'sliding sleeve'. [citation needed]

The wellbore for a plug and perf job is generally composed of standard joints of steel casing, either cemented or uncemented, which is set in place at the conclusion of the drilling process. Once the drilling rig has been removed, a wireline truck is used to perforate near the end of the well, following which a fracturing job is pumped (commonly called a stage). Once the stage is finished, the wireline truck will set a plug in the well to temporarily seal off that section, and then perforate the next section of the wellbore. Another stage is then pumped, and the process is repeated as necessary along the entire length of the horizontal part of the wellbore. [citation needed]

The wellbore for the sliding sleeve technique is different in that the sliding sleeves are included at set spacings in the steel casing at the time it is set in place. The sliding sleeves are usually all closed at this time. When the well is ready to be fractured, using one of several activation techniques, the bottom sliding sleeve is opened and the first stage gets pumped. Once finished, the next sleeve is opened which concurrently isolates the first stage, and the process repeats. For the sliding sleeve method, wireline is usually not required. [citation needed]

These completion techniques may allow for more than 30 stages to be pumped into the horizontal section of a single well if required, which is far more than would typically be pumped into a vertical well. [citation needed]

Chemicals

Water is by far the largest component of fracking fluids. The initial drilling operation itself may consume from 65,000 gallons to 600,000 gallons of fracking fluids. Over its lifetime an average well will require up to an additional 5 million gallons of water for the initial fracking operation and possible restimulation frac jobs.[56] The large volumes of water required have raised concerns about fracking in arid areas, such as Karoo in South Africa.[57]

Chemical additives used in fracturing fluids typically make up less than 2% by weight of the total fluid.[58] Over the life of a typical well, this may amount to 100,000 gallons of chemical additives. These additives (listed in a U.S. House of Representatives Report[59]) include biocides, surfactants, viscosity-modifiers, and emulsifiers. They vary widely in toxicity: Many are used in household products such as cosmetics, lotions, soaps, detergents, furniture polishes, floor waxes, and paints,[60] and some are used in food products. Some, however, are known carcinogens, some are toxic, and some are neurotoxins. For example: benzene (causes cancer, bone marrow failure), lead (damages the nervous system and causes brain disorders), ethylene glycol (antifreeze, causes death), methanol (highly toxic), boric acid (kidney damage, death), 2-butoxyethanol (causes hemolysis). Gamma-emitting isotopes (radioactive; can cause cancer) are also included in the fluid as tracers. Some of the isotopes used are Antimony-121, Antimony-122, Antimony-123, Antimony-124, Antimony-125, Antimony-126, Antimony-127, Chromium-51, Cobalt-57, Cobalt-58, Cobalt-60, Gold-198, Iodine-127, Iodine-128, Iodine-129, Iodine-130, Iodine-131, Iridium-192, Iron-59, Krypton-85, Lanthanum-140, Potassium-39 (activated to Potassium-40), Potassium-41 (activated to Potassium-42), Potassium-43, Rubidium-86, Scandium-45, Scandium-46, Scandium-47, Scandium-48, Silver-110, Strontium-85, Xenon-133, Zinc-65, and Zirconium-95. Several are typically combined and injected together.[52][53][54] Their half lifes range from 40.2 hours (Lanthanum-140) to 5.27 years (Cobalt-60).[61]

Despite concerns about the generally elevated radiation levels found near hydraulic fracturing sites and high levels of iodine-131 (a radioactive tracer used in hydraulic fracturing) found in drinking water and milk, [62][63][64] iodine-131 is not listed among the chemicals to be monitored in the United States Environmental Protection Agency Hydraulic Fracturing Draft Study Plan. Other known radioactive tracers used in hydraulic fracturing [52][53][54] but not listed as chemicals to be studied include radioactive isotopes of gold, xenon, rubidium, iridium, scandium, and krypton.[5]. Recently the EPA has not been very forthcoming regarding public disclosure of environmental contamination by the oil and gas industry.[25][65]

The 2011 US House of Representatives investigative report on the chemicals used in hydraulic fracturing shows that of the 750 compounds in hydraulic fracturing products “[m]ore than 650 of these products contained chemicals that are known or possible human carcinogens, regulated under the Safe Drinking Water Act, or listed as hazardous air pollutants” (12). The report also shows that between 2005 and 2009 279 products (93.6 million gallons-not including water) had at least one component listed as “proprietary” or “trade secret” on their Occupational Safety and Health Administration (OSHA) required Material Safety Data Sheet (MSDS). The MSDS is a list of chemical components in the products of chemical manufacturers, and according to OSHA, a manufacturer may withhold information designated as “proprietary” from this sheet. When asked to reveal the proprietary components, most companies participating in the investigation were unable to do so, leading the committee to surmise these “companies are injecting fluids containing unknown chemicals about which they may have limited understanding of the potential risks posed to human health and the environment” (12).[66] Without knowing the identity of the proprietary components, regulators cannot test for their presence. This prevents government regulators from establishing baseline levels of the substances prior to hydraulic fracturing and documenting changes in these levels, thereby making it impossible to prove that hydraulic fracturing is contaminating the environment with these substances.[67] Third-party laboratories are performing analyses on soil, air, and water near the fracturing sites to measure the level of contamination by some of the known chemicals, but not the proprietary substances, involved in hydraulic fracturing. Each state has a contact person in charge of such regulation.[68] A map of these contact people can be found at FracFocus.org as well.[69]

Another 2011 study identified 632 chemicals used in natural gas operations. Only 353 of these are well-described in the scientific literature; and of these, more than 75% could affect skin, eyes, respiratory and gastrointestinal systems; roughly 40-50% could affect the brain and nervous, immune and cardiovascular systems and the kidneys; 37% could affect the endocrine system; and 25% were carcinogens and mutagens. The study indicated possible long-term health effects that might not appear immediately. The study recommended full disclosure of all products used, along with extensive air and water monitoring near natural gas operations; it also recommended that fracking's exemption from regulation under the US Safe Drinking Water Act be rescinded.[70]

Some states have started requiring natural gas companies to "disclose the names of all chemicals to be stored and used a drilling site," keeping a record on file at the state’s environmental agency, such as the case in Pennsylvania with the Department of Environmental Protection and in New York with the Department of Environmental Conservation.[71] However, the continuing concern of some activists who oppose hydraulic fracturing is the lack of information really provided. According to Weston Wilson in Affirming Gasland, "about 50% or so of these MSDS sheets lack a specific chemical name, and some MSDS sheets simply claim 'proprietary' status and list none of the chemicals in that container."[72] As a result, some activists are calling for specific disclosure of chemicals used, such as the Chemical Abstract Service (CAS) number and specific chemical formulas, and increased access to such information. In his State of the Union address for 2012, Barack Obama stated his intention to force fracking companies to disclose the chemicals they use,[73] though the subsequent, proposed guidelines were criticised for failing to specify how drillers will disclose the chemicals they use.[74]

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 — Initial 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 three major functions:
  1. Open and extend the fracture.
  2. Transport the proppant along the fracture length.
  3. Transport radioactive tracers through the fractures to determine the injection profile and track the locations of fractures.[52][51][53][54]
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.

Environmental concerns

Environmental concerns with hydraulic fracturing include the potential contamination of ground water, risks to air quality, the potential migration of gases and hydraulic fracturing chemicals to the surface, the potential mishandling of waste, and the health effects of these, like cancer.[59][75] Many cases of suspected groundwater contamination have been documented.[76] Valerie Brown, a researcher and science writer, believes that with the explosive growth of natural gas wells in the US, public exposure to the many chemicals involved in hydraulic fracturing is increasing, with uncertain consequences.[75]

Challenges to research

It has been reported that Industry and governmental pressure have made it difficult to conduct and report the results of comprehensive studies of hydraulic fracturing. EPA investigations into the oil and gas industry's environmental impact have been narrowed in scope and/or had negative findings removed due to industry and government pressure[25][77][78] A 2012 Cornell University report noted that it was difficult to assess health impact because of legislation, proprietary secrecy, and non-disclosure agreements that allow them to keep the proprietary chemicals used in the fluid secret. Cornell researcher Bamberger stated that if you don't know what chemicals are, you can't conduct pre-drilling tests and establish a baseline to prove that chemicals found postdrilling are from hydraulic fracturing.[79] The researchers recommended requiring disclosure of all hydraulic fracturing fluids, that nondisclosure agreements not be allowed when public health is at risk, testing animals raised near hydraulic fracturing sites and animal products (milk, cheese, etc.) from animal raised near hydraulic fracturing sites prior to selling them to market, monitoring of water, soil and air more closely, and testing the air, water, soil and animals prior to drilling and at regular intervals thereafter.[79] In addition, after court cases concerning contamination from hydraulic fracturing are settled, the documents are sealed. While the American Petroleum Institute deny that this practice has hidden problems with gas drilling, others believe it has and could lead to unnecessary risks to public safety and health.[80]

New York State Assembly members Robert Castelli and Steve Katz call for a moratorium on hydraulic fracturing in the Croton Watershed in October 2010.

The New York Times reported that the results of the 2004 EPA Study were censored due to strong industry influence and political pressure,[25] however EPA agency officials stood by the results.[citation needed] An early draft of the study discussed the possibility of dangerous levels of fracking fluid contamination, and mentioned "possible evidence" of aquifer contamination. The final report concluded simply that fracking "poses little or no threat to drinking water".[25] The study's scope was narrowed so that it only focused on the injection of fracking fluids, ignoring other aspects of the process such as disposal of fluids, and environmental concerns such as water quality, fish kills and acid burns. The study was concluded before public complaints of contamination started emerging.[81]: 780  The study's conclusion that the injection of fracking fluids into coalbed methane (CBM) wells posed a minimal threat to underground drinking water sources[82] may have influenced the 2005 Congressional decision to exempt hydraulic fracturing from regulation under the Safe Drinking Water Act.

The 2012 EPA Hydraulic Fracturing Draft Plan was also narrowed. It does not include studying the effects of iodine-131 (found in Philadelphia's drinking water)[62][83][64] or other radioactive tracer isotopes used in hydraulic fracturing.[52][53][54][6] Nor does the draft plan include evaluating the impact of wastewater. Christopher Portier, director of the US CDC's National Center for Environmental Health and the Agency for Toxic Substances and Disease Registry, argued that, in addition to the EPA's plans to investigate the impact of fracking on drinking water, additional studies should be carried out to determine whether wastewater from the wells can harm people or animals and vegetables they eat.[84] A group of US doctors called for a moratorium on fracking in populated areas until such studies had been done.[41][85]

Proponents of hydraulic fracturing have erroneously reported in the press and other media that the recent University of Texas Study ("Fact-Based Regulation for Environmental Protection in Shale Gas Development") found that hydraulic fracturing caused no environmental contamination,[86][87] when in fact the study found that all steps in the process except the actual injection of the fluid (which proponents artificially separated from the rest of the process and designated "hydraulic fracturing") have resulted in environmental contamination.[24] The radioactivity of the injected fluid itself was not assessed in the University of Texas study.[24] While the EPA recognizes the potential for contamination of water by hydraulic fracturing, EPA Administrator Lisa Jackson testified in a Senate Hearing Committee stating that she is not aware of any proof where the fracking process itself has contaminated water.[88]

Air emissions and pollution

One group of emissions associated with natural gas development and production, are the emissions associated with combustion. These emissions include particulate matter, nitrogen oxides, sulfur oxide, carbon dioxide and carbon monoxide. Another group of emissions that are routinely vented into the atmosphere are those linked with natural gas itself, which is composed of methane, ethane, liquid condensate, and volatile organic compounds (VOCs). The VOCs that are especially impactful on health are benzene, toluene, ethyl benzene, and xylene (referred to as a group, called BTEX). Health effects of exposure to these chemicals include neurological problems, birth defects, and cancer.[89]

VOCs, including BTEX, mixed with nitrogen oxides from combustion and combined with sunlight can lead to ozone formation. Ozone has been shown to impact lung function, increase respiratory illness, and is particularly dangerous to lung development in children.[70] In 2008, measured ambient concentrations in the rural Sublette County, Wyoming where ranching and natural gas are the main industries were frequently above the National Ambient Air Quality Standards (NAAQS) of 75ppb and have been recorded as high as 125 ppb.[90] However, a study for the city of Fort Worth, TX, examining air quality around natural gas sites "did not reveal any significant health threats."[91] The Fort Worth Star-Telegram characterized that report as "the most comprehensive study of urban gas drilling to date."[92]

Groundwater contamination

Despite barriers to research, there are documented incidents of contamination. As early as 1987, an E.P.A. report was published that indicated fracture fluid invasion into James Parson's water well in Jackson County, West Virginia. The well, drilled by Kaiser Exploration and Mining Company, was found to have induced fractures that created a pathway to allow fracture fluid to contaminate the groundwater from which Mr. Parson's well was producing. The oil and gas industry and the E.P.A. disagreed regarding the accuracy and thoroughness of this report.[80] In 2006 drilling fluids and methane were detected leaking from the ground near a gas well in Clark, Wyoming; 8 million cubic feet of methane were eventually released, and shallow groundwater was found to be contaminated.[75] Directed by Congress, the U.S. EPA announced in March 2010 that it will examine claims of water pollution related to hydraulic fracturing.[77]

In Garfield County, Colorado, another area with a high concentration of drilling rigs, volatile organic compound emissions increased 30% between 2004 and 2006; during the same period there was a rash of health complaints from local residents. Epidemiological studies that might confirm or rule out any connection between these complaints and fracking are virtually non-existent. The health effects of VOCs are largely unquantified, so any causal relationship is difficult to ascertain; however, some of these chemicals are suspected carcinogens and neurotoxins.[75] Investigators from the Colorado School of Public Health performed a study in Garfield regarding potential adverse health effects, and concluded that residents near gas wells might suffer chemical exposures, accidents from industry operations, and psychological impacts such as depression, anxiety and stress. This study (the only one of its kind to date) was never published, owing to disagreements between community members and the drilling company over the study's methods.[93]

In 2009 13 water wells Dimock, Pennsylvania were contaminated with methane (one blew up). Cabot Oil & Gas had to financially compensate residents and construct a pipeline to bring in clean water. The company continues to deny that any "of the issues in Dimock have anything to do with hydraulic fracturing".[81][94][95][96] The devices needed to prevent such water contamination cost as little as $600.[97] Confusion remains regarding whether the water in Dimock is safe to drink. On Dec. 2, 2011, EPA sent an email to several Dimock residents indicating that their well water presented no immediate health threat. On Jan. 19, 2012, the EPA reversed its position, and asked that the agency’s hazardous site cleanup division take immediate action to protect public health and safety.[98]

In 2010 the film Gasland premiered at the Sundance Film Festival. The filmmaker claims that chemicals including toxins, known carcinogens, and heavy metals polluted the ground water near well sites in Pennsylvania, Wyoming, and Colorado.[99] The film was criticized by oil and gas industry group[100] Energy in Depth as factually inaccurate;[101] in response, a detailed rebuttal of the claims of inaccuracy has been posted on Gasland's website.[102]

Complaints about water quality from residents near a gas field in Pavillion, Wyoming prompted an EPA groundwater investigation. The EPA reported detections of methane and other chemicals such as phthalates in private water wells.[103] An EPA draft report dated December 8, 2011 suggested that the ground water in the Pavillion, Wyoming, aquifer contains "compounds likely associated with gas production practices, including hydraulic fracturing".[104][105][106] The EPA discovered traces of methane and foaming agents in several water wells near a gas rig. Samples of water taken from EPA’s deep monitoring wells in the aquifer were found to contain gasoline, diesel fuel, BTEX (benzene, toluene, ethylbenzene, xylene), naphthalenes, isopropanol, and synthetic chemicals (e.g., glycols and alcohols) used in gas production and hydraulic fracturing fluid, and high methane levels. Benzene concentrations in the samples were well above Safe Drinking Water Act standards.[104] The EPA report stated concerns about the movement of contaminants within the aquifer and the future safety of drinking water in the context of the area’s complex geology. EPA's sampling of Pavillion area drinking water wells found chemicals consistent with those reported in previous EPA reports, including but not limited to methane and other petroleum hydrocarbons, indicating migration of contaminants from areas of gas production.[104] The report also said that contaminants in wells near pits indicated that (frack) pits are a source of shallow ground water contamination. It also said, "Detections of organic chemicals are more numerous and exhibit higher concentrations in the deeper of the two monitoring wells … (which) along with trends in methane, potassium, chloride, and pH, suggest a deep source of contamination." Their observations of chemical reactions in the field led them to suggest that upward migration of chemicals from deep underground is the culprit. They also found that the reports companies filed detailing jobs listed chemicals as a class or as "proprietary," "rendering identification of constituents impossible."[107]}} The draft report also stated: "Alter­na­tive expla­na­tions were care­fully con­sid­ered to explain indi­vid­ual sets of data. How­ever, when con­sid­ered together with other lines of evi­dence, the data indi­cates likely impact to ground water that can be explained by hydraulic fracturing."[108] Industry figures rejected the EPA's findings.[109] In response, in 2010 the U.S. Department of Health and Human Services’ Agency for Toxic Substances and Disease Registry recommended that owners of tainted wells use alternate sources of water for drinking and cooking, and ventilation when showering. These recommendations were still in place as of December 2011. Encana is funding the alternate water supplies.[104]During the investigation Luke Chavez (EPA investigator), commented that the contaminants could have come from cleaning products or oil and gas production, but said that in either case, their presence suggested problematic practices.[94]

It is important to note that not every instance of groundwater methane contamination is a result of hydraulic fracturing. Often, local water wells drill through many shale and coal layers that can naturally seep methane into the producing groundwater. This methane is often biogenic (created by organic material decomposition) in origin as opposed to thermogenic (created through "thermal decomposition of buried organic material"[110]). Thermogenic methane is the methane most often sought after by oil & gas companies deep in the earth, whereas biogenic methane is found in shallower formations (where water wells are typically drilled). Through isotope analysis and other detection methods, it is often fairly easy to determine whether the methane is biogenic or thermogenic, and thus determine from where it is produced.[110] The presence of thermogenic methane does not confirm the source of gas. The gas composition and isotopic finger print must compared by experts with other known sources of gas to confirm a match.[111]

In 2011 a Duke University study published in Proceedings of the National Academy of Sciences examined methane in groundwater in Pennsylvania and New York states overlying the Marcellus Shale and the Utica Shale. It determined that groundwater tended to contain much higher concentrations of methane near fracking wells, with potential explosion hazard; the methane's isotopic signatures and other geochemical indicators were consistent with it originating in the fracked deep shale formations, rather than any other source.[19]

The 2011 University of Texas study described the environmental impact of each of the separate parts of the overall hydraulic fracturing process, or "phases of the shale gas development life cycle."[24] These parts include of (1) drill pad construction and operation, (2) the construction, integrity, and performance of the wellbores, (3) the injection of the fluid once it is underground (which proponents consider the actual "fracking"), (4) the flowback of the fluid back towards the surface, (5) blowouts, often unreported, which spew hydraulic fracturing fluid and other byproducts across surrounding area, (5) integrity of other pipelines involved and (6) the disposal of the flowback, including waste water and other waste products.[87][86] Associated problems include (1) Groundwater Contamination, (2) Blowouts and House Explosions, (3) Water Consumption and Supply, (4) Spill Management and Surface Water Protection, (5) Atmospheric Emissions, (6) Health Effects[24] All but the injection stage were reported to be sources of contamination in the University of Texas study.[24] The study concluded that if hydraulic fracturing is to be conducted in an environmentally safe manner, these issues need to be addressed first.[24] Proponents have reported that groundwater contamination doesn't come directly from the "fracking" part of the process (the injection of hydraulic fracturing chemicals into Shale rock formations) but from other parts of the hydraulic fracturing process. Injection cannot be accomplished, however, without the accompanying stages. Poorly constructed or damaged wellbores and pipelines can allow the fluid to flow into aquifers.[24] Volatile chemicals held in waste water evaporation ponds can to evaporate into the atmosphere, or overflow. In one of the cases described by a 2012 Cornell University study (conducted in Colorado, Louisiana, New York, Ohio, Pennsylvania and Texas) impounded wastewater was released into a field and pond, killing at least 70 animals.[79] The runoff can also end up in groundwater systems. Groundwater may become contaminated by trucks carrying fracking chemicals and wastewater if they are involved in accidents on the way to fracking sites or disposal destinations. Disposal of fracking fluid by injection can cause earthquakes, and release of unprocessed or under-processed waste water into rivers can contaminate water supplies.[24] Critics have noted that it is "difficult for researchers to be objective if their university receives a lot of grants and funds from the industry.”[112] An Energy Institute spokesperson said that the study was not funded by the industry. He said funds came from the university, which has a variety of funding sources.[112] There are extensive links between UT and the oil & gas industry, with the giving of Royal Dutch Shell to the university currently standing at more than $24.8 million, $4m alone having been handed over for 2012.[113][114] Since 2011, Shell has partnered Texas in a program called Shell-UT Unconventional Research, and the university has a similar research program in place with Exxon Mobil.[115] Halliburton, the largest supplier of fracking services in the United States, has also given millions of dollars to the university.[116] Statoil announced a $5m research agreement (part of which will focus on oil shale) with UT's Bureau of Economic Geology in September 2011, whose program director, Ian Duncan, was the senior contributor for the parts of the Texas study to do with the environmental impacts of shale gas development.[16][24][117]

In DISH, Texas, elevated levels of disulphides, benzene, xylenes and naphthalene have been detected in the air, alongside numerous local complaints of headaches, diarrhea, nosebleeds, dizziness, muscle spasms and other problems.[citation needed] Additionally, the Colorado Oil & Gas Conservation Commission has found some wells containing thermogenic methane due to oil and gas development upon investigating complaints from residents.[118] Cause-and-effect relationships have not been established.[93]

A 2011 report by the Massachusetts Institute of Technology addressed groundwater contamination, noting "There has been concern that these fractures can also penetrate shallow freshwater zones and contaminate them with fracturing fluid, but there is no evidence that this is occurring. There is, however, evidence of natural gas migration into freshwater zones in some areas, most likely as a result of substandard well completion practices by a few operators. There are additional environmental challenges in the area of water management, particularly the effective disposal of fracture fluids". This study encourages the use of industry best practices to prevent such events from recurring.[119]

Radioactive contamination

The New York Times has reported radiation in hydraulic fracturing wastewater released into rivers in Pennsylvania.[120] It collected data from more than 200 natural gas wells in Pennsylvania and has posted a map entitled Toxic Contamination from Natural Gas Wells in Pennsylvania. Sand containing gamma-emitting tracer isotopes is used to trace and measure fractures.[52] The Times stated "never-reported studies" by the United States Environmental Protection Agency and a "confidential study by the drilling industry" concluded that radioactivity in drilling waste cannot be fully diluted in rivers and other waterways.[121] Despite this, as of early 2011 federal and state regulators did not require sewage treatment plants that accept drilling waste (which is mostly water) to test for radioactivity. In Pennsylvania, where the drilling boom began in 2008, most drinking-water intake plants downstream from those sewage treatment plants have not tested for radioactivity since before 2006.[122] The New York Times reporting has predictably been criticized by aggrieved parties,[123] but one venerable science writer has taken issue with one instance of the newspaper's presentation and explanation of its calculations regarding dilution,[124] charging that a lack of context made the article's analysis uninformative.[125]

According to a Times report in February 2011, wastewater at 116 of 179 deep gas wells in Pennsylvania "contained high levels of radiation," but its effect on public drinking water supplies is unknown because water suppliers are required to conduct tests of radiation "only sporadically".[126] The New York Post stated that the Pennsylvania Department of Environmental Protection reported that all samples it took from seven rivers in November and December 2010 "showed levels at or below the normal naturally occurring background levels of radioactivity", and "below the federal drinking water standard for Radium 226 and 228."[127] However the samples taken by the state at at least one river, (the Monongahela, a source of drinking water for parts of Pittsburgh), were taken upstream from the sewage treatment plants accepting drilling waste water.[128]

In Pennsylvania, much of this wastewater from hydraulic fracturing operations is processed by public sewage treatment plants. However, many sewage plants say that they are incapable of removing the radioactive components of this waste, which is often released into major rivers. Industry officials, though, claim that these levels are diluted enough that public health is not compromised.[120] This is a major concern as it provides the possibility for radioactive waste to enter into public water supplies. In April 2011, Environmental Protection Agency (EPA) found elevated iodine-131 levels in Philadelphia's drinking water and milk from Little Rock, Arkansas.[62][129] The National Cancer Institute has reported that children exposed to iodine-131, especially those drinking a great deal of milk, may have an increased risk of thyroid cancer. [130] Both Philadelphia and Little Rock are located downstream from shale formations in which hydraulic fracturing is occurring. Iodine-131 was also found in the drinking water of other cities near other hydrofracturing sites.[62][131][132]

In response to the Environmental Protection Agency (EPA) findings, the Philadelphia Water Department also posted a notice that Iodine-131 had been found in the water supply.[133] The notice omits the fact that Iodine-131 is popular radioactive tracer used in hydrofracturing fluid to determine the injection profile and location of fractures created by hydraulic fracturing,[51] and is mentioned in multiple hydraulic fracturing technology patents.[52][53][54] In the notice, the Philadelphia Water Department attributes the presence of Iodine-131 to nuclear energy production and the March 2011 Japanese nuclear incident instead. When iodine-131 was still found in the Wissahickon Creek, and at several sewage treatment plants along the creek near Philadelphia in late July, long after the fallout from the Japanese incident would have decayed, Philadelphia Water Department officials became concerned.[134][64] They reviewed Philadelphia's U.S. Environmental Protection Agency records and found that iodine-131 had been found in several Philadelphia drinking water samples long before the Fukushima accident. In fact, Environmental Protection Agency (EPA) records showed that Philadelphia's iodine-131 levels were the highest in the last decade in the set of those measured at 59 locations across the United States.[64] The Philadelphia Water Department is currently attributing the elevated levels to cancer patients' urine from undetermined sources because iodine-131 is used in the treatment of thyroid cancer.[64] The EPA and the Philadelphia Water Department are not specifically acknowledging that iodine-131, a radioactive tracer used in hydraulic fracturing since at least 1976,[52] may be coming from the hydraulic fracturing wastewater released into the rivers.[64] The EPA, however, is concerned about radionuclide levels in drinking water. The EPA has asked the Pennsylvania Department of Environmental Protection (PDEP) to require "community water systems (CWSs) near publicly owned treatment works (POTWs) and centralized wastewater treatment (CWT) facilities receiving Marcellus Shale wastewater to conduct sampling immediately for radionuclides." They note that "in previous monitoring, radionuclides were not detected or were detected at levels less than one-half of maximum contaminant levels," but that "the CWS have not sampled after the introduction of Marcellus Shale operations. The EPA letter adds that "Discharges from these operations could increase radionuclide levels substantially."[135] The warning about iodine-131 was still posted on the Philadelphia Water Department web site as of February 25, 2012.[133]

The New York Times has implicated the DEP in industry-friendly inactivity, requesting rather than requiring them to handle their own flowback waste rather than sending it to public water treatment facilities.[136] However, former Pennsylvania DEP Secretary John Hanger, who served under Gov. Ed Rendell (D), has affirmed that municipal drinking water throughout the state is safe, but added that the environmentalists were accurate in stating that Pennsylvania's water treatment plants were not equipped to treat hydraulic fracturing water.[137] Current Pennsylvania DEP Secretary Michael Krancer serving under Gov. Tom Corbett (R) has denied that untreated wastewater is being discharged into the state's waterways.[138] It has been observed that Corbett received over a million dollars in gas industry contributions,[139] more than all his competitors combined, during his election campaign.[5] The New York Times reported that regulations are lax in Pennsylvania.[120] The oil and gas industry is generally left to police itself in the case of accidents. Unannounced inspections are not made by regulators: the companies report their own spills, and create their own remediation plans.[120] A recent review of the state-approved plans found them to appear to be in violation of the law.[120] Treatment plants are still not equipped to remove radioactive material and are not required to test for it.[120] Despite this, in 2009 the Ridgway Borough’s public sewage treatment plant, in Elk County, PA, facility was sent wastewater containing radium and other types of radiation at at 275-780 times the drinking-water standard. The water being released from the plant was not tested for radiation levels.[120] Part of the problem is that growth in waste produced by the industry has outpaced regulators and state resources.[120] It should be noted that "safe drinking water standards" have not yet been set for many of the substances known to be in hydrofracturing fluids or their radioactivity levels,[120] and their levels are not included in public drinking water quality reports.[140]

Earthquakes

A report in the UK concluded that fracking was the likely cause of some small earth tremors that happened during shale gas drilling.[141][142][143] In addition, the United States Geological Survey (USGS) reports that, "Earthquakes induced by human activity have been documented in a few locations" in the United States, Japan, and Canada, "the cause [of which] was injection of fluids into deep wells for waste disposal and secondary recovery of oil, and the use of reservoirs for water supplies."[144] The disposal and injection wells referenced are regulated under the Safe Drinking Water Act and UIC laws and are not wells where hydraulic fracturing is generally performed.[citation needed]

Several earthquakes—including a substantial, magnitude 4.0 one on New Year's Eve—that had hit Youngstown, Ohio, throughout 2011 are likely linked to a disposal well for injecting wastewater used in the hydraulic fracturing process, according to seismologists at Columbia University.[145]

Greenhouse gas emissions

The use of natural gas rather than oil or coal is often viewed as a way of alleviating global warming: natural gas burns more cleanly, and gas power stations can produce up to 50% less greenhouse gases than coal stations.[146] However, an analysis by Howarth et al. of the well-to-consumer lifecycle of fracked natural gas concluded that 3.6–7.9% of the methane produced by a well will be leaked into the atmosphere during the well's lifetime. According to the analysis, methane is such a potent greenhouse gas, this means that over short timescales, shale gas is actually worse than coal or oil. Methane gradually breaks down in the atmosphere, forming carbon dioxide, so that over very long periods it is no more problematic than carbon dioxide; in the meantime, even if shale gas is burnt in efficient gas power stations, its greenhouse-gas footprint is still worse than coal or oil for timescales of less than fifty years.[147] This analysis by Howarth et al. refers to the 2011 study by the same authors published in Climatic Change Letters in which they controversially claimed that the extraction of shale gas may lead to the emission of as much or more greenhouse gas emissions than oil or coal.[148] However, several studies have argued that the paper was flawed and/or come to completely different conclusions, including assessments by experts at the US Department of Energy,[149] by Carnegie Mellon University[150] and the University of Maryland,[151] as well as by the Natural Resources Defense Council, which concluded that the Howarth et al. paper's use of a 20-year time horizon for global warming potential of methane is "too short a period to be appropriate for policy analysis."[152] In January 2012, Howarth's colleagues at Cornell University responded with their assessment, arguing that the Howarth paper was "seriously flawed" because it "significantly overestimate[s] the fugitive emissions associated with unconventional gas extraction, undervalue[s] the contribution of 'green technologies' to reducing those emissions to a level approaching that of conventional gas, base[s] their comparison between gas and coal on heat rather than electricity generation (almost the sole use of coal), and assume[s] a time interval over which to compute the relative climate impact of gas compared to coal that does not capture the contrast between the long residence time of CO2 and the short residence time of methane in the atmosphere."[153] The authors of that response conclude that "shale gas has a GHG footprint that is half and perhaps a third that of coal," based upon "more reasonable leakage rates and bases of comparison." Howarth et al. responded to this criticism: "We stand by our approach and findings. The latest EPA estimate for methane emissions from shale gas falls within the range of our estimates but not those of Cathles et al, which are substantially lower."[154][155]

Public relations

The considerable opposition against fracking activities in local townships has led companies to adopt a variety of public relations measures to assuage fears about fracking, including the admitted use of "mil­i­tary tac­tics to counter drilling oppo­nents". At a conference where public relations measures were discussed, a senior executive at Anadarko Petroleum was recorded on tape saying, "Download the US Army / Marine Corps Counterinsurgency Manual, because we are dealing with an insurgency", while referring to fracking opponents. Matt Pitzarella, spokesman for the most important fracking company in Pennsylvania, Range Resources, also told other conference attendees that Range employed psychological warfare operations veterans. According to Pitzarella, the experience learnt in the Middle East has been valuable to Range Resources in Pennsylvania, when dealing with emotionally-charged township meetings and advising townships on zoning and local ordinances dealing with fracking.[156][157] Furthermore, in a February 2012 campaign speech, Rick Santorum, a candidate for the 2012 Republican Party presidential nomination, claimed opponents of hydraulic fracturing were trying to scare people in a "reign of environmental terror".[158]He accused President Obama of catering to "radical environmental groups"[158] although President Obama supports the practice of hydraulic fracturing as well.[159]

Hydraulic fracturing by country

Main article: Hydraulic fracturing by country

Hydraulic fracturing has become a contentious environmental and health issue with France banning the practice and a moratorium in place in New South Wales (Australia), Karoo basin (South Africa), Quebec (Canada), and some of the states of the US.

See also

Notes

a. ^ Also spelled "fraccing"[160] or "fracing".[161][162]

References

  1. ^ Charlez, Philippe A. (1997). Rock Mechanics: Petroleum Applications. Paris: Editions Technip. p. 239.
  2. ^ "Definition of frac job". Oilfield Glossary. Schlumberger. Retrieved 22 February 2012.
  3. ^ a b c Anthony Andrews; et al. (30 October 2009). "Unconventional Gas Shales: Development, Technology, and Policy Issues" (PDF). Congressional Research Service. Retrieved 22 February 2012. {{cite web}}: Explicit use of et al. in: |author= (help)
  4. ^ Charlez (1997). Rock Mechanics. p. 239.
  5. ^ a b Bill McKibben (8 March 2012). "Why Not Frack?". The New York Review of Books. 59 (4). Retrieved 21 February 2012.
  6. ^ "World Energy Outlook 2011: Are We Entering a Golden Age of Gas?" (PDF). International Energy Agency. 9 November 2011. Retrieved 3 March 2012. Based on the assumptions of the GAS Scenario, from 2010 gas use will rise by more than 50% and account for over 25% of world energy demand in 2035—surely a prospect to designate the Golden Age of Gas.
  7. ^ Ian Urbina (28 January 2012). "New Report by Agency Lowers Estimates of Natural Gas in U.S." The New York Times. Retrieved 23 February 2012.
  8. ^ Rich Miller, Asjylyn Loder and Jim Polson (7 February 2012). "Americans Gaining Energy Independence With U.S. as Top Producer". Bloomberg. Retrieved 21 February 2012.
  9. ^ a b Gies, Erica (24 February 2012). "Push to Export Natural Gas Could Threaten U.S. Energy Security". Green Tech. Forbes. Retrieved 4 March 2012.
  10. ^ a b "LNG Exports Dominion Receives DOE Authorization to Export LNG". Dominion. October 2011. Retrieved 6 March 2012.
  11. ^ Barnhardt, Laura (19 April 2006). "Firm to hold meetings on LNG pipeline plan". Baltimore Sun. Retrieved 6 March 2012.
  12. ^ "$1B natural gas pipeline proposed for Pa., would connect to Baltimore, DC areas". Associate Press. 2 March 2012. Retrieved 6 March 2012.
  13. ^ Barnhardt, Laura (12 August 2008). "Information sessions on LNG pipeline Federal officials to meet with property owners about route (correction)". Baltimore Sun. Retrieved 4 March 2012.
  14. ^ Rascoe, Ayesha (7 February). "Sierra Club opposes Maryland LNG export terminal". Reuters. Retrieved 5 March 2012. {{cite web}}: Check date values in: |date= (help)
  15. ^ Prezioso, Jeanine (28 July 2011). "Analysis: U.S. shale gas sector girds for next battle: pipeline". Reuters. Retrieved 6 March 2012.
  16. ^ a b Scott, Mark (17 October 2011). "Norway's Statoil to Acquire Brigham Exploration for $4.4 Billion". Dealb%k. New York Times. Retrieved 4 March 2012.
  17. ^ Polson, Jim, & Haas, Benjamin (4 February). "Sinopec Group to Buy Stakes in Devon Energy Oil Projects". Bloomberg Businessweek. Retrieved 4 March 2012. {{cite web}}: Check date values in: |date= (help)CS1 maint: multiple names: authors list (link)
  18. ^ Carroll, Joe & Polson, Jim (9 January). "U.S. Shale Bubble Inflates After Near-Record Prices for Untested Fields". Bloomberg Businessweek. Retrieved 4 March 2012. {{cite web}}: Check date values in: |date= (help)CS1 maint: multiple names: authors list (link)
  19. ^ a b Osborn, Stephen G.; Vengosh, Avner; Warner, Nathaniel R.; Jackson, Robert B. (2011-05-09). "Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing". Proceedings of the National Academy of Sciences. doi:10.1073/pnas.1100682108. Retrieved 2011-10-14.
  20. ^ "Expanded Site Investigation - Analytical Results Report, Pavillion Area Groundwater Report" (PDF). U.S. EPA Region 8. August 30, 2010.
  21. ^ David Biello (30 March 2010). "What the Frack? Natural Gas from Subterranean Shale Promises U.S. Energy Independence--With Environmental Costs". Scientific American. Retrieved 21 February 2012. {{cite web}}: |author= has generic name (help); External link in |author= (help)CS1 maint: numeric names: authors list (link)
  22. ^ Daphne Wysham (6 February 2012). "Fracking Perils: A Dangerous Misstep on the Road to U.S. Energy Independence". Common Dreams. Retrieved 22 February 2012.
  23. ^ "Incidents where hydraulic fracturing is a suspected cause of drinking water contamination". U.S. NRDC. December 2011. Retrieved 23 February 2012.
  24. ^ a b c d e f g h i j "Fact-Based Regulation for Environmental Protection in Shale Gas Development" (PDF). Retrieved 29 February 2012.
  25. ^ a b c d e Ian Urbina (3 March 2011). "Pressure Limits Efforts to Police Drilling for Gas". The New York Times. Retrieved 23 February 2012.
  26. ^ Daphne Wysham (6 February 2012). "Fracking Perils: A Dangerous Misstep on the Road to U.S. Energy Independence". Common Dreams. Retrieved 22 February 2012.
  27. ^ Editorial (16 February 2012). "Energy Independence Gives Opening for Renewables". Bloomberg. Retrieved 21 February 2012.
  28. ^ Charlez (1997). Rock Mechanics. p. 239.
  29. ^ "Wikipedia: Shale Gas Geology"
  30. ^ "National Research Council, 1988, A review of the management of the Gas Research Institute"
  31. ^ The Breakthrough Institute. Interview with Dan Steward, former Mitchell Energy Vice President. December 2011.
  32. ^ "US Government Role in Shale Gas Fracking: An Overview"
  33. ^ Fjaer, E. (2008). "Mechanics of hydraulic fracturing". Petroleum related rock mechanics. Developments in petroleum science (2 ed.). Elsevier. p. 369. ISBN 9780444502605. Retrieved 6 March 2012.
  34. ^ Price, N.J.; Cosgrove, J.W. (1990). Analysis of geological structures. Cambridge University Press. pp. 30–33. ISBN 9780521319584. Retrieved 5 November 2011.
  35. ^ Manthei, G.; Eisenblätter, J.; Kamlot, P. (2003). "Stress measurement in salt mines using a special hydraulic fracturing borehole tool". In Natau, Fecker & Pimentel (ed.). Geotechnical Measurements and Modelling (PDF). pp. 355–360. ISBN 9058096033. Retrieved 6 March 2012.
  36. ^ Zoback, M.D. (2007). Reservoir geomechanics. Cambridge University Press. p. 18. Retrieved 6 March 2012.
  37. ^ Laubach, S.E. (2004). "Coevolution of crack-seal texture and fracture porosity in sedimentary rocks: cathodoluminescence observations of regional fractures". Journal of Structural Geology. 26 (5). Elsevier: 967–982. doi:10.1016/j.jsg.2003.08.019. Retrieved 5 November 2011. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  38. ^ Sibson, R.H. (1975). "Seismic pumping--a hydrothermal fluid transport mechanism". Journal of the Geological Society. 131. London: Geological Society: 653–659. doi:10.1144/gsjgs.131.6.0653. Retrieved 5 November 2011. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  39. ^ Gill, R. (2010). Igneous rocks and processes: a practical guide. John Wiley and Sons. p. 102. ISBN 9781444330656. Retrieved 5 November 2011.
  40. ^ "The Barnett Shale" (PDF). North Keller Neighbors Together.
  41. ^ a b David Wethe (19 January 2012). "Like Fracking? You'll Love 'Super Fracking'". Businessweek. Retrieved 22 January 2012.
  42. ^ "Production Decline of a Natural Gas Well Over Time". Geology.com. The Geology Society of America. 3 January 2012. Retrieved 4 March 2012.
  43. ^ Gidley, J.L. et al. (editors), "Recent Advances in Hydraulic Fracturing", SPE Monograph, SPE, Richardson, Texas, 1989.
  44. ^ Yew, C.H., "Mechanics of Hydraulic Fracturing", Gulf Publishing Company, Houston, Texas, 1997.
  45. ^ Economides, M.J. and K.G. Nolte (editors), "Reservoir Stimulation", John Wiley & Sons, Ltd., New York, 2000.
  46. ^ 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); Unknown parameter |month= ignored (help)
  47. ^ Brown, Edwin Thomas (2007) [2003]. Block Caving Geomechanics (2nd ed.). Indooroopilly, Queensland: Julius Kruttschnitt Mineral Research Centre, UQ. ISBN 978-0-980-36220-6.
  48. ^ Frank, U.; Barkley, N. (February 1995). "Remediation of low permeability subsurface formations by fracturing enhancement of soil vapor extraction". Journal of Hazardous Materials. 40 (2): 191–201. doi:10.1016/0304-3894(94)00069-S. ISSN 0304-3894. {{cite journal}}: More than one of |work= and |journal= specified (help)
  49. ^ "Geothermal Technologies Program: How an Enhanced Geothermal System Works". .eere.energy.gov. 2011-02-16. Retrieved 2011-11-02.
  50. ^ a b Ground Water Protection Council; ALL Consulting (2009), Modern Shale Gas Development in the United States: A Primer (PDF), DOE Office of Fossil Energy and National Energy Technology Laboratory, retrieved 24 February 2012 {{citation}}: External link in |author1= and |author2= (help); Unknown parameter |month= ignored (help); Unknown parameter |separator= ignored (help)
  51. ^ a b c Reis, John C. (1976). Environmental Control in Petroleum Engineering. Gulf Professional Publishers.
  52. ^ a b c d e f g h [1] Scott III, George L. (03-June-1997) US Patent No. 5635712: Method for monitoring the hydraulic fracturing of a subterranean formation. US Patent Publications.
  53. ^ a b c d e f [2]Fertl; Walter H. (15-Nov-1983) US Patent No. US4415805: Method and apparatus for evaluating multiple stage fracturing or earth formations surrounding a borehole. US Patent Publications.
  54. ^ a b c d e f [3] Scott III, George L. (15-Aug-1995) US Patent No. US5441110: System and method for monitoring fracture growth during hydraulic fracture treatment. US Patent Publications.
  55. ^ Seale, Rocky (July/August 2007). "Open hole completion systems enables multi-stage fracturing and stimulation along horizontal wellbores" (PDF). Drilling Contractor (Fracturing stimulation ed.). Retrieved October 1, 2009. {{cite journal}}: Check date values in: |date= (help)
  56. ^ "Water Usage". Chesapeake Energy site hydraulicfracturing.com.
  57. ^ Ian Urbina (30 December 2011). "Hunt for Gas Hits Fragile Soil, and South Africans Fear Risks". The New York Times. Retrieved 23 February 2012. Covering much of the roughly 800 miles between Johannesburg and Cape Town, this arid expanse—its name [Karoo] means "thirsty land"—sees less rain in some parts than the Mojave Desert.
  58. ^ http://www.hydraulicfracturing.com/Fracturing-Ingredients/Pages/information.aspx
  59. ^ a b "Chemicals Used in Hydraulic Fracturing" (PDF). Committee on Energy and Commerce U.S. House of Representatives. April 18, 2011.
  60. ^ "Household Products Database". U.S. Department of Health and Human Services.
  61. ^ [4] Gadeken, Larry L., Halliburton Company (08-Nov-1989). Radioactive well logging method.
  62. ^ a b c d Jeff McMahon (10 April 2011). "EPA: New Radiation Highs in Little Rock Milk, Philadelphia Drinking Water". Forbes. Retrieved 22 February 2012.
  63. ^ "Japanese Nuclear Emergency: Radiation Monitoring". EPA. 30 June 2011. Retrieved 23 February 2012.
  64. ^ a b c d e f Sandy Bauers (21 July 2011). "Cancer patients' urine suspected in Wissahickon iodine-131 levels". Philadelphia inquirer, Carbon County Groundwater Guardians. Retrieved 25 February 2012. Cite error: The named reference "Carbon County" was defined multiple times with different content (see the help page).
  65. ^ "Documents: Natural Gas's Toxic Waste". New York Times. 2011-02-26. Retrieved 2 May 2011.
  66. ^ Chemicals Used in Hydraulic Fracturing. U.S. House of Representatives Committee on Energy and Commerce Minority Staff. April 2011. http://democrats.energycommerce.house.gov/sites/default/files/documents/Hydraulic%20Fracturing%20Report%204.18.11.pdf
  67. ^ Kris Fitz Patrick (November 17, 2011). ["http://sites.duke.edu/sjpp/2011/ensuring-safe-drinking-water-in-the-age-of-hydraulic-fracturing/" "Ensuring Safe Drinking Water in the Age of Hydraulic Fracturing"]. {{cite web}}: Check |url= value (help)
  68. ^ ["http://www.caslab.com/Fracking-Regulations/" "Fracking Regulations"]. {{cite web}}: Check |url= value (help)
  69. ^ About Gas: Regulation. http://www.aboutgas.com.au/regulation.html.
  70. ^ a b Colborn, Theo; Kwiatkowski, Carol; Schultz, Kim; Bachran, Mary (2011). "Natural Gas Operations from a Public Health Perspective" (PDF). Human and Ecological Risk Assessment: An International Journal. 17 (5). Taylor & Francis: 1039–1056. doi:10.1080/10807039.2011.605662.
  71. ^ "Energy In Depth" (PDF). Gasland Debunked.
  72. ^ Josh Fox, “Affirming Gasland,” http://www.damascuscitizens.org/Affirming-GASLAND.pdf
  73. ^ Ed Crooks (25 January 2012). "US set to require disclosure from 'frackers'". The Financial Times. Retrieved 26 January 2012.
  74. ^ Katarzyna Klimasinska (7 February 2012). "Draft Fracking Rule Has 'Good Elements,' Environmentalist Says". Businessweek. Retrieved 22 February 2012. The draft of the measure only says the information "will become a matter of public record." . . . Among his [Dusty Horwitt, senior counsel of the Environmental Working Group] concerns are an exemption from disclosure of trade secrets. "Our concern is whether the exemption would swallow the rule," he said.
  75. ^ a b c d Template:Cite article
  76. ^ "Incidents where hydraulic fracturing is a suspected cause of drinking water contamination". U.S. NRDC. December 2011. Retrieved 23 February 2012.
  77. ^ a b "EPA's Study of Hydraulic Fracturing and Its Potential Impact on Drinking Water Resources". EPA. Retrieved 24 February 2010.
  78. ^ "Documents: The Debate Over the Hydrofracking Study's Scope". NYTimes.com. 3 March 2011. Retrieved 23 February 2012.
  79. ^ a b c Ramanuja, Krishna (7 Martch 2012). "Study suggests hydrofracking is killing farm animals, pets". Cornell Chronicle Online. Cornell University. Retrieved 9 March 2012. {{cite web}}: Check date values in: |date= (help)
  80. ^ a b Ian Urbina (3 August 2011). "A Tainted Water Well, and Concern There May be More". The New York Times. Retrieved 22 February 2012.
  81. ^ a b Template:Cite article
  82. ^ "Evaluation of Impacts to Underground Sources of Drinking Water by Hydraulic Fracturing of Coalbed Methane Reservoirs; National Study Final Report" (PDF). EPA. June 2004. Retrieved 23 February 2011.
  83. ^ "Japanese Nuclear Emergency: Radiation Monitoring". EPA. 30 June 2011. Retrieved 23 February 2012.
  84. ^ Alex Wayne (4 January 2012). "Health Effects of Fracking Need Study, Says CDC Scientist". Businessweek. Retrieved 29 February 2012.
  85. ^ Mark Drajem (11 January 2012). "Fracking Political Support Unshaken by Doctors' Call for Ban". Bloomberg. Retrieved 19 January 2012.
  86. ^ a b Vaughan, Vicki (16 February 2012). "Fracturing 'has no direct' link to water pollution, UT study finds". Retrieved 3 March 2012.
  87. ^ a b Munro, Margaret (17 February 2012). "Fracking does not contaminate groundwater: study released in Vancouver". Retrieved 3 March 2012.
  88. ^ "Pathways To Energy Independence: Hydraulic Fracturing And Other New Technologies". U.S. Senate. May 6, 2011.
  89. ^ "Toxicology and human health effects following exposure to oxygenated or reformulated gasoline" (PDF). US EPA. May 2001. {{cite journal}}: Cite journal requires |journal= (help)
  90. ^ "Ozone mitigation efforts continue in Sublette County, Wyoming". Wyoming's Online News Source. March 2011.
  91. ^ "City of Fort Worth: Natural Gas Air Quality Study" (PDF). July 13, 2011.
  92. ^ "Study: No 'significant health threats' from natural gas sites in Fort Worth". Fort Worth Star-Telegram. July 15, 2011.
  93. ^ a b Schmidt, Charles W. "Blind Rush? Shale Gas Boom Proceeds Amid Human Health Questions". Environmental Health Perspectives (119(1)).
  94. ^ a b Jad Mouawad (7 December 2009). "Dark Side of a Natural Gas Boom". The New York Times. Retrieved 3 March 2012. {{cite news}}: Unknown parameter |coauthor= ignored (|author= suggested) (help)
  95. ^ Christopher Bateman (21 June 2010). "A Colossal Fracking Mess". VanityFair.com. Retrieved 3 March 2012.
  96. ^ Jim Snyder (10 January 2012). "Pennsylvania Fracking Foes Fault EPA Over Tainted Water Response". Bloomberg. Retrieved 19 January 2012. {{cite news}}: Unknown parameter |coauthor= ignored (|author= suggested) (help)
  97. ^ Jim Efstathiou Jr. (23 December 2012). "Fracking Opens Fissures Among States as Drillers Face Many Rules". Bloomberg. Retrieved 19 January 2012. {{cite news}}: Unknown parameter |coauthor= ignored (|author= suggested) (help)
  98. ^ "The Facts Behind EPA's Dimock Two-Step". 01/23/12. Retrieved 02/09/12. {{cite news}}: Check date values in: |accessdate= and |date= (help)
  99. ^ "Gasland". 2010.
  100. ^ Honan, Edith (2010-06-17). "Film challenges safety of U.S. shale gas drilling". Reuters. Retrieved 2010-06-28.
  101. ^ Energy in Depth (June 9, 2010). "Debunking GasLand" (PDF). Retrieved December 17, 2011.
  102. ^ "Affirming Gasland" (PDF). 2010-07. Retrieved 2010-12-21. {{cite news}}: Check date values in: |date= (help)
  103. ^ "Expanded Site Investigation - Analytical Results Report, Pavillion Area Groundwater Report" (PDF). U.S. EPA Region 8. August 30, 2010.
  104. ^ a b c d Larry Jackson (8 December 2011). [http://yosemite.epa.gov/opa/admpress.nsf/1e5ab1124055f3b28525781f0042ed40/ef35bd26a80d6ce3852579600065c94e! OpenDocument "EPA Releases Draft Findings of Pavillion, Wyoming Ground Water Investigation for Public Comment and Independent Scientific Review"]. Retrieved 27 February 2012. {{cite news}}: Check |url= value (help); line feed character in |url= at position 108 (help)
  105. ^ "Groundwater Investigation: Pavillion, WY". EPA. Retrieved 6 February 2012. Pavillion, Wyoming is located in Fremont County, about 20 miles northwest of Riverton. In 2003, the estimated population was 166 residents. The concern at the site is potential groundwater contamination, based on resident complaints about smells, tastes and adverse changes in water quality of their domestic wells. The report itself is here.
  106. ^ Christopher Helman (8 December 2011). "What If Fracking Did Pollute Wyoming Water?". Forbes.com. Retrieved 6 February 2012.
  107. ^ "EPA Releases Report on Water Contamination By Fracking, As GA Pushes Fee Bills". PhillyNow blog. Philadelphia Weekly. 9 December 2011. Retrieved 6 February 2012.
  108. ^ Susan Phillips (8 December 2011). "EPA Blames Fracking for Wyoming Groundwater Contamination". StateImpact Penn­syl­va­nia. WITF, WHYY & NPR. Retrieved 6 February 2012. {{cite web}}: soft hyphen character in |work= at position 17 (help)
  109. ^ Jim Efstathiou (8 December 2011). "Gas-Fracking Chemicals Detected in Wyoming Aquifer, EPA Says". Bloomberg. Retrieved 6 February 2011.
  110. ^ a b Department of Natural Resources. "Gasland Correction Document". Denver, CO. State of Colorado Oil & Gas Conservation Commission. p. 1. {{cite news}}: |format= requires |url= (help)
  111. ^ "Methane in Pennsylvania water wells unrelated to Marcellus shale fracturing". Oil & Gas Journal. Retrieved 14 March 2012.
  112. ^ a b "Fracturing 'has no direct' link to water pollution, UT study finds". Fuel Fix. 17 February 2012. Retrieved 20 March 2012.
  113. ^ "Shell Oil Company Invests Nearly $4 Million in The University of Texas at Austin". UT Austin website. 14 February 2012. Retrieved 5 March 2012.
  114. ^ Sandra Zaragoza (15 February 2012). "Shell Oil invests $3.9M in UT". Houston Business Journal. Retrieved 5 March 2012.
  115. ^ Brett Clanton (13 September 2011). "Shell, UT to study better shale production methods". Houston Chronicle. Retrieved 5 March 2011.
  116. ^ "Halliburton Gives $90,000 in Grants to The University of Texas at Austin". UT Austin website. 28 February 2007. Retrieved 5 March 2012. Energy services company Halliburton has contributed $90,000 to support academic programs at The University of Texas at Austin, bringing the company's total university giving to nearly $7 million.
  117. ^ Barry Harrell (19 September 2011). "Norway-based energy company, UT agree on $5 million research program". The Austin American-Statesman. Retrieved 5 March 2012.
  118. ^ "Gasland Correction Document" (PDF). Colorado Oil & Gas Conservation Commission. Retrieved 25 January 2012.
  119. ^ "The Future of Natural Gas: An Interdisciplinary MIT Study" (PDF). MIT Energy Initiative. June 2011. {{cite journal}}: Cite journal requires |journal= (help)
  120. ^ a b c d e f g h i Ian Urbina (26 February 2011). "Regulation Lax as Gas Wells' Tainted Water Hits Rivers". The New York Times. Retrieved 22 February 2012.
  121. ^ "Documents: Natural Gas's Toxic Waste". New York Times. February 26, 2011. {{cite journal}}: Cite journal requires |journal= (help)
  122. ^ "Regulation Lax as Gas Wells' Tainted Water Hits Rivers". New York Times. February 26, 2011. {{cite journal}}: Cite journal requires |journal= (help)
  123. ^ "Natural Gas Drilling, the Spotlight". The New York Times. 5 March 2011. Retrieved 24 February 2012.
  124. ^ Ian Urbina (1 March 2011). "Drilling Down: Wastewater Recycling No Cure-All in Gas Process". The New York Times. Retrieved 22 February 2012.
  125. ^ Charles Petit (2 March 2011). "Part II of the fracking water problems in PA and other Marcellus Shale country". Knight Science Journalism Tracker. MIT. Retrieved 24 February 2012. {{cite web}}: External link in |author= (help)
  126. ^ Don Hopey (5 March 2011). "Radiation-fracking link sparks swift reactions". Pittsburgh Post-Gazette. Retrieved 23 February 2012.
  127. ^ Shocker: New York Times radioactive water report is false March 8, 2011 ι Abby Wisse Schachter. Report is from a Rupert Murdoch tabloid, The New York Post
  128. ^ Ian Urbina (7 March 2011). "E.P.A. Steps Up Scrutiny of Pollution in Pennsylvania Rivers". The New York Times. Retrieved 23 February 2012.
  129. ^ "Japanese Nuclear Emergency: Radiation Monitoring". EPA. 30 June 2011. Retrieved 23 February 2012.
  130. ^ "Press release: NCI Completes Nationwide Study of Radioactive Fallout from 1950s Nuclear Tests". National Cancer Institute. Retrieved 25 February 2012.
  131. ^ "Find a Well". FracFocus Chemical Disclosure Registry. 11 January 2011. Retrieved 23 February 2012.
  132. ^ "Don't Get Fracked (maps)". Natural Resources Defense Council. 16 September 2011. Retrieved 23 February 2012.
  133. ^ a b "Iodine 131 Found in Philadelphia's Drinking Water" (PDF). Philadelphia Water Department. April 12, 2011. Retrieved 12 February 2012.
  134. ^ Sandy Bauers (21 July 2011). "Cancer patients' urine suspected in Wissahickon iodine-131 levels (short version)". Philadelphia inquirer. Retrieved 25 February 2012.
  135. ^ March 7, 2011 Letter from the EPA to Pennsylvania Department of Environmental Protection
  136. ^ Griswold, Eliza (17 November 2011). "The Fracturing of Pennsylvania". The New York Times Magazine. Retrieved 21 November 2011.
  137. ^ "State Official: Pa. Water Meets Safe Drinking Standards". CBS Pittsburgh. January 4, 2011.
  138. ^ "Pennsylvania DEP Secretary Defends States' Ability to Regulate Hydraulic Fracturing". PR Newswire. November 17, 2011.
  139. ^ Don Hopey (February 24, 2011). "Corbett repeals policy on gas drilling in parks". Pittsburgh Post-Gazette. Retrieved April 19, 2011.
  140. ^ "Annual Drinking Water Quality Report, 2010" (PDF). Philadelphia Water Department. Spring 2011. Retrieved 7 February 2012.
  141. ^ BBC News (8 June 2011). "Shale gas fracking: MPs call for safety inquiry after tremors". BBC. Retrieved 22 February 2012.
  142. ^ BBC News (2 November 2011). "Fracking tests near Blackpool 'likely cause' of tremors". BBC. Retrieved 22 February 2012.
  143. ^ C.J. de Pater and (2 November 2011). "Geomechanical Study of Bowland Shale Seismicity" (PDF). Cuadrilla Resources. Retrieved 22 February 2012. {{cite web}}: Unknown parameter |coauthor= ignored (|author= suggested) (help)
  144. ^ "FAQs - Earthquakes, Faults, Plate Tectonics, Earth Structure: Can we cause earthquakes? Is there any way to prevent earthquakes?". USGS. 27 October 2009. Retrieved 22 February 2012.
  145. ^ "Ohio Quakes Probably Triggered by Waste Disposal Well, Say Seismologists". Lamont-Doherty Earth Observatory Institute, Columbia University. 6 January 2012. Retrieved 22 February 2012.
  146. ^ Engelder, Terry (15 September 2011). "Should Fracking Stop? Extracting gas from shale increases the availability of this resource, but the health and environmental risks may be too high. Counterpoint: No, it's too valuable". Nature (477): 271–275.
  147. ^ Howarth, Robert W.; Ingraffea, Anthony (15 September 2011). "Should Fracking Stop? Extracting gas from shale increases the availability of this resource, but the health and environmental risks may be too high. Point: Yes, it's too high risk". Nature (477): 271–275.
  148. ^ Howarth, Robert W.; Santoro, Renee; Ingraffea, Anthony (2011). "Methane and the greenhouse gas footprint of natural gas from shale formations". Climatic Change. 106 (4): 679–690. doi:10.1007/s10584-011-0061-5. {{cite journal}}: |access-date= requires |url= (help)
  149. ^ Skone, Timothy J. (12 May 2011). "Life Cycle Greenhouse Gas Analysis of Natural Gas Extraction & Delivery in the United States" (PDF). National Energy Technology Laboratory. Retrieved 4 February 2012.
  150. ^ Mohan Jiang; et al. (2011). "Life cycle greenhouse gas emissions of Marcellus shale gas". Environmental Research Letters. 6 (3). doi:10.1088/1748-9326/6/3/034014. {{cite journal}}: |access-date= requires |url= (help); Explicit use of et al. in: |author= (help)
  151. ^ Nathan Hultman; et al. (2011). "The greenhouse impact of unconventional gas for electricity generation". Environmental Research Letters. 6 (4). doi:10.1088/1748-9326/6/4/044008. {{cite journal}}: |access-date= requires |url= (help); Explicit use of et al. in: |author= (help)
  152. ^ Lashof, Dan (12 April 2011). "Natural Gas Needs Tighter Production Practices to Reduce Global Warming Pollution". Natural Resources Defense Council. Retrieved 4 February 2012.
  153. ^ Cathles, Lawrence M.; Brown, Larry; Taam, Milton; Hunter, Andrew (2011). Climatic Change. doi:10.1007/s10584-011-0333-0. {{cite journal}}: |access-date= requires |url= (help); Missing or empty |title= (help)
  154. ^ Howarth, Robert W.; Santoro, Renee; Ingraffea, Anthony (2012). "Venting and leaking of methane from shale gas development: Response to Cathles et al" (PDF). Climatic Change. Retrieved 4 February 2012. Article is currently in press.
  155. ^ Stephen Leahy (24 January 2012). "Shale Gas a Bridge to More Global Warming". IPS. Retrieved 4 February 2012.
  156. ^ Javers, Eamon (8 Nov 2011). "Oil Executive: Military-Style 'Psy Ops' Experience Applied". CNBC.
  157. ^ Phillips, Susan (9 Nov 2011). "'We're Dealing with an Insurgency,' says Energy Company Exec of Fracking Foes". National Public Radio.
  158. ^ a b Adam Aigner-Treworgy. "Santorum takes on 'environmental terror'". CNN. Retrieved 24 February 2012.
  159. ^ Erich Schwartzel (29 January 2012). "Obama's backing of shale gas aimed at voters in Marcellus region". Pittsburgh Post-Gazette. Retrieved 29 January 2012.
  160. ^ "Chemicals that may be used in Australian CSG fraccing fluid" (PDF). Australian Petroleum Ptoduction & Exploration Association Limited. Retrieved 22 February 2012.
  161. ^ Stephen D. Simpson (12 July 2010). "Will The EPA Crack Down On 'Fracking'?". Investopedia. Retrieved 22 February 2012.
  162. ^ "HydraulicFracturing.com". HydraulicFracturing.com. Retrieved 2011-07-13.
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