Hydraulic fracturing

"Fracking" redirects here. For the expletive, see Frak (expletive).

Tower for hydraulic fracturing of 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 or hydrofracking. This type of fracturing, known colloquially as a 'frac job', creates fractures from a wellbore drilled into reservoir rock formations. The first frac job was performed in 1947, though the current fracking technique was first used in the late 1990s in the Barnett Shale in Texas. 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.

Proponents of fracking point to the vast amounts of formerly inaccessible hydrocarbons the process can extract: in the United States, for example, fracking may be able to retrieve quantities of gas equivalent to half a century's worth of national consumption, a concomitant being a return of the country's energy independence. There are environmental concerns, however, regarding the contamination of ground water, risks to air quality, the migration of gases and hydraulic fracturing chemicals to the surface, and the health effects of these.

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. This latter practice has come under scrutiny internationally, with some countries suspending it, or even banning it completely.

Mechanics

Fracturing in rocks at depth is suppressed by the confining pressure, particularly in the case of tensile (Mode 1) fractures which require the walls of the fracture to move apart. Hydraulic fracturing occurs when the effective stress is reduced sufficiently by an increase in the pressure of fluids in the rock such that the minimum principal stress becomes tensile and exceeds the tensile strength of the material. 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. In natural examples, such as dikes or vein-filled fractures, their orientations can be used to infer past stress states.

Natural examples

Rocks often contain evidence of past hydraulic fracturing events, where fluids have passed through tensile fractures.

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. 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'.

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.

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. 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.

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

• Stimulating groundwater wells
• Preconditioning rock for caving or inducing rock to cave in mining
• As a means of enhancing waste remediation processes, usually hydrocarbon waste or spills
• 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

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, 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. 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. 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. 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. 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. 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. 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.

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.

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. The large volumes of water required have raised concerns about fracking in arid areas, such as Karoo in South Africa.

Chemical additives used in fracturing fluids typically make up less than 2% by weight of the total fluid. 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) 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, 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. Their half lifes range from 40.2 hours (Lanthanum-140) to 5.27 years (Cobalt-60).

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, 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 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.

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). 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. 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. A map of these contact people can be found at FracFocus.org as well.

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.

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. 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." 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, though the subsequent, proposed guidelines were criticised for failing to specify how drillers will disclose the chemicals they use.

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.

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. Many cases of suspected groundwater contamination have been documented.

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

In the US, interviews with Environmental Protection Agency (EPA) scientists and leaked documents have shown that, since the 1980s, EPA investigations into the oil and gas industry's environmental impact—including the ongoing one into fracking's potential impact on drinking water—and associated reports had been narrowed in scope and/or had negative findings removed due to industry and government pressure.

A fairly recent example of this is a 2004 study by the EPA, which concluded that the injection of fracking fluids into coalbed methane (CBM) wells posed a minimal threat to underground drinking water sources. An early draft of the study discussed the possibility of dangerous levels of fracking-fluid contamination, and mentioned "possible evidence" of aquifer contamination; both these points were absent from the final report, which concluded simply that fracking "poses little or no threat to drinking water". An agency whistle-blower said shortly after publication that the absence could be explained by strong industry-influence and political pressure. The narrowing of scope for this particular study meant it only focused on the injection of fracking fluids, while 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 also concluded before public complaints of contamination started emerging. In 2005, hydraulic fracturing was exempted by US Congress from any regulation under the Safe Drinking Water Act, possibly due to this EPA report.

With the explosive growth of natural gas wells in the US, researcher Valerie Brown predicted in 2007 that "public exposure to the many chemicals involved in energy development is expected to increase over the next few years, with uncertain consequences." As development of natural gas wells in the U.S. since the year 2000 has increased, so too have claims by private well owners of water contamination. This has prompted EPA and others to re-visit the topic.

While the EPA recognizes the potential for contamination of water by hydraulic fracturing, EPA Administrator Lisa Jackson testified in a Senate Hearing Committee stating "I'm not aware of any proven case where the fracking process itself has affected water...". One reason for a seeming lack of documentation is the current practice of sealing the documents after a court case. While the American Petroleum Institute "dismissed the assertion that sealed settlements have hidden problems with gas drilling," some feel it represents an unnecessary risk to public safety and health. Despite these setbacks, there are, however, 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. There still however exists much contention between the oil and gas industry and the E.P.A. on the accuracy and thoroughness of this report. 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.In the town of Dimock, Pennsylvania, 13 water wells were contaminated with methane (one of them blew up), and the gas company, Cabot Oil & Gas, had to financially compensate residents and construct a pipeline to bring in clean water; the company continued to deny, however, that any "of the issues in Dimock have anything to do with hydraulic fracturing". The devices needed to prevent such water contamination cost as little as $600. 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.

Early in January 2012, 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. A week later, a group of US doctors called for a moratorium on fracking in populated areas until such studies had been done. Despite this, President Obama voiced his support for the practice during his State of the Union address at the end of the month.

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.

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. 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. However, a study for the city of Fort Worth, TX, examining air quality around natural gas sites "did not reveal any significant health threats." The Fort Worth Star-Telegram characterized that report as "the most comprehensive study of urban gas drilling to date."

Groundwater contamination

A Duke University study published in Proceedings of the National Academy of Sciences in 2011 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. 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. However, 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"). 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.

A draft report released by the EPA on December 8, 2011 suggested that the ground water in the Pavillion, Wyoming, aquifer contains "compounds likely associated with gas production practices, including hydraulic fracturing". 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 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. 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. In response, 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 reccomendations were made in 2010 and were still in place as of December 2011. Encana is funding the alternate water supplies.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.

Recent reports have 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." 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 they 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. 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 It has been 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. Wellbores and pipelines can have faulty construction or be damaged during the process, allowing the fluid to flow into aquifers. The waste water evaporation ponds allow the volatile chemicals in the waste water to evaporate into the atmosphere. The ponds may overflow when it rains, and the runoff will eventually makes its way into groundwater systems. Groundwater may become contaminated when poorly constructed pipelines used to transport the waste water to water treatment plants leak or break, allowing the waste water and fracking chemicals to flow into groundwater systems. The transportation by trucks and storage of fracking chemicals allows for groundwater to become contaminated when accidents happen during transportation to the fracking site or to its disposal destination. Disposal of fracking fluid by injection can cause earthquakes, and release of unprocessed or under-processed waste water into rivers can contaminate water supplies.

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. Individuals "smell things that don't make them feel well, but we know nothing about cause-and-effect relationships in these cases." 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. 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.

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.

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.

Directed by Congress, the U.S. EPA announced in March 2010 that it will examine claims of water pollution related to hydraulic fracturing.

Having investigated complaints about water quality in Pavillion, Wyoming, the EPA released its draft report in December 2011.

The report results aren't pretty. Wading through a mess of chemical terms and testing jargon, we get to the nitty gritty: "detections of high concentrations of benzenes, xylenes, gasoline range organics, diesel range organics and … hydrocarbons in ground water samples from … wells near pits indicates that (frack) pits are a source of shallow ground water contamination," the report says.

At some wells the researchers found "water near-saturated in methane" and in deep water wells, they also found chemicals used during the fracking process: gasoline, diesel fuel, BTEX (benzene, toluene, ethylbenzene, xylene), naphthalenes, isopropanol, and a whole slew of other things that you’d rather not drink. The report continues: "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."

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." Industry figures rejected the EPA's findings.

Radioactive contamination

The New York Times has reported radiation in hydraulic fracturing wastewater released into rivers in Pennsylvania. 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. 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. 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. The New York Times reporting has predictably been criticized by aggrieved parties, but one venerable science writer has taken issue with one instance of the newspaper's presentation and explanation of its calculations regarding dilution, charging that a lack of context made the article's analysis uninformative.

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". 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." 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.

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. 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. 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. 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.

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. 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, and is mentioned in multiple hydraulic fracturing technology patents. 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. 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. 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. The EPA and the Philadelphia Water Department are not acknowledging that iodine-131, a radioactive tracer used in hydraulic fracturing since at least 1976, may be coming from the hydraulic fracturing wastewater released into the rivers. The warning about iodine-131 was still posted on the Philadelphia Water Department web site as of February 25, 2012.

The New York Times has implicated the DEP in industry-friendly inactivity, such as only making a "request — not a regulation" of gas companies to handle their own flowback waste rather than sending them to public water treatment facilities. 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. "Every single drop that is coming out of the tap in Pennsylvania today meets the safe drinking water standard," Hanger said, but added that the environmentalists were accurate in stating that Pennsylvania's water treatment plants were not equipped to treat hydraulic fracturing water. Current Pennsylvania DEP Secretary Michael Krancer serving under Gov. Tom Corbett (R) has said it is "total fiction" that untreated wastewater is being discharged into the state's waterways, though it has been observed that Corbett received over a million dollars in gas industry contributions, more than all his competitors combined, during his election campaign. The New York Times reported that regulations are lax in Pennsylvania. 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. A recent review of the state-approved plans found them to appear to be in violation of the law. Treatment plants are still not equipped to remove radioactive material and are not required to test for it. 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. Part of the problem is that growth in waste produced by the industry has outpaced regulators and state resources. 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, and their levels are not included in public drinking water quality reports.

Earthquakes

A report in the UK concluded that fracking was the likely cause of some small earth tremors that happened during shale gas drilling. 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." 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.

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. 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. 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. 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, by Carnegie Mellon University and the University of Maryland, 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." 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." 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."

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. Furthermore, in a February 2012 campaign speech, Rick Santorum, a candidate for the 2012 Republican Party presidential nomination, referred to those objecting to hydraulic fracturing as environmental terrorists.

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.

Australia

Up until the mid 2000s, hydraulic fracturing was generally limited to conventional oil and gas wells in the Cooper Basin and limited to one, two or sometimes zero ongoing fracturing operations. However more recently, it has spread and grown in Queensland as coal seam gas drilling and production in the Surat and Bowen basins has rapidly increased. However the vast majority of coal seam gas wells have not been hydraulically fractured as the wells presently being drilled are in coal seams that have good natural permeability.

On 21 February 2011, the ABC's investigative journalism program Four Corners aired a program showing incidents of wellhead gas leaks (unrelated to hydraulic fracturing) and alleged aquifer contamination near Chinchilla, Queensland at wells owned by QGC, some of which had been hydraulically fractured.

There is currently a moratorium in place on the practice of hydraulic fracturing in the state of New South Wales.^{[citation needed]}. The moratorium will not affect exploration, drilling core holes and getting core samples. The NSW Government's restrictions on hydraulic fracturing apply to new licences only. The NSW Government has banned BTEX chemicals as additives. It also requires companies to hold a water licences for extraction of more than three megalitres per year and has banned the use of evaporation ponds.^{[citation needed]}

Bulgaria

A number of protests occurred in Bulgaria after the government's decision to grant an approval for Chevron Corporation to research the possibilities of shale gas extraction in the country's northeast in 2011. After a nationwide protest in January 2012, the government decided to ban the hydraulic fracturing technology.

Canada

Fracking has been in use in Canada at an industrial level since the 1990s. Concerns about fracking began in late July 2011, when the Government of British Columbia gave Talisman Energy a long-term water licence to draw water from the BC Hydro-owned Williston Lake reservoir, for a twenty year term. Fracking has also received criticism in New Brunswick and Nova Scotia, and the Nova Scotia government is currently reviewing the practice, with recommendations expected in March 2012. The practice has been temporarily suspended, in Quebec, pending an environmental review. The Canadian Centre for Policy Alternatives has also expressed concern.

China

China completed its first horizontal shale gas well in 2011. A global shale gas study by the US Energy Information Administration said China's technically recoverable shale gas reserves were almost 50% higher than those of the number two nation, the United States.

France

Hydraulic fracturing was banned in France in 2011 after public pressure.

Ireland

In Northern Ireland, Tamboran Resources has tested sites in County Fermanagh which they claim could supply gas to Northern Ireland for years to come. Tamboran Resources also has a license for gas exploration and plan to proceed hydraulic fracturing in the Lough Allen basin area of County Leitrim. The CEO of Tamboran Resources has declared a “zero-chemical hydraulic fracturing” pledge. The Protest group "No Fracking Ireland" has been set up by locals of counties Leitrim, Roscommon and Sligo and petitions against hydraulic fracturing are still ongoing.

New Zealand

In New Zealand, hydraulic fracturing is part of petroleum exploration and extraction on a small scale mainly in Taranaki and concerns have been raised by environmentalists.

South Africa

There is currently a moratorium on hydraulic fracturing in South Africa's Karoo region despite the interest of several energy companies.

United Kingdom

Main article: Hydraulic fracturing in the United Kingdom

Fracking is carried out in the United Kingdom by Cuadrilla Resources, though other companies have exploration licenses. Though not officially suspended, the process has not been carried out in the UK since June 2011, when Cuadrilla's operations caused two small earthquakes in Lancashire. Protest groups have emerged, including Frack Off and a number of local groups.

United States

Main article: Hydraulic fracturing in the United States

Hydraulic fracturing is most commonly used in the United States to extract natural gas from shale formations, with advances in the technology meaning shale gas has increased to 30 percent of US gas production over the past 15 years. Because of the impermeability of shale, the gas industry of the 1970s could not economically extract shale gas. Following direct investments in R&D and demonstration in massive hydraulic fracturing, directional drilling, and microseismic 3-dimensional imaging by the Department of Energy and other federal agencies, Mitchell Energy applied an innovative technique called slick-water fracturing to achieve the first economical well for the extraction of shale gas in 1998.

Hydraulic fracturing for the purpose of oil, natural gas, and geothermal production was exempted under the Safe Drinking Water Act. This was a result of the signage of the Energy Policy Act of 2005, also known as the Halliburton Loophole because of former Halliburton CEO Vice President Dick Cheney’s involvement in the passing of this exemption. The result of a 2004 EPA study on coalbed hydraulic fracturing was used to justify the passing of the exemption; however EPA whistleblower Weston Wilson and the Oil and Gas Accountability Project found that critical information was removed from the final report. Halliburton is the leading provider of fracking services in the United States.

Opposers of hydraulic fracturing in the US have focused on this 2005 exemption; however the more primary risk to drinking water is the handling and treatment of wastewater produced by hydraulic fracturing. The EPA and the state authorities do have power "to regulate discharge of produced waters from hydraulic operations" (EPA, 2011) under the Clean Water Act, which is regulated by the National Pollutant Discharge Elimination System (NPDES) permit program. Although this waste is regulated, oil and gas exploration and production (E&P) wastes are exempt from Federal Hazardous Waste Regulations under Subtitle C of the Resource Conservation and Recovery Act (RCRA) despite the fact that wastewater from hydraulic fracturing contains toxins such as total dissolved solids (TDS), metals, and radionuclides. About 750 chemicals have been listed as additives for hydraulic fracturing in a report to the US Congress in 2011. However, well-specific information can be found on FracFocus.org. Companies are still not required to provide the names of chemicals in "proprietary" formulas, so the chemical lists are incomplete.

See also

• ExxonMobil Electrofrac
• Gasland, a 2010 documentary by Josh Fox exploring the environmental impacts of hydraulic fracturing
• Eddy covariance, a method to directly measure emissions of gases displayed by hydraulic fracturing into the atmosphere
• Cost of electricity by source
• Environmental impact of the oil shale industry
• Environmental impact of petroleum
• Environmental concerns with electricity generation

Notes

a. ^{^} Also spelled "fraccing" or "fracing".

External links

• Hydraulic Fracturing slanted toward environmental issues at Earthworks
• Fracking collected news and commentary at ProPublica
• Shale gas and fracking collected news and commentary at The Guardian
• FracFocus Site indicating chemical composition of fracking fluid of individual wells
• Hydraulic fracturing shale gas extraction at YouTube