Hydraulic fracturing

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Tight gas ” well in the Pinedale - anticline in the US state of Wyoming , with the Rocky Mountains in the background
Halliburton fracking plant at the head of a well in the Bakken Formation , North Dakota

Hydraulic fracturing or fracking for short (from English to fracture , 'to break up', 'to tear open'; also called " hydraulic fracturing ", "fracing", fracturing or frac jobs , German also hydraulic fracturing , hydraulic breaking open , hydraulic crack generation or hydraulic stimulation ) is one Method for the creation, expansion and stabilization of cracks in the rock of a deposit in the deep subsurface with the aim of increasing the permeability of the deposit rock . As a result, the gases or liquids contained therein can flow more easily and more consistently to the bore and can be extracted.

In fracking , a liquid (“fracfluid”) is pressed into the geological horizon from which the production is to be carried out through a borehole under high pressure of typically several hundred bar . The Fracfluid is water, which is usually mixed with proppants, such as. B. quartz sand , and thickeners is added. Usually several deflected bores (laterals) are first created in the target horizon by means of directional drilling , with the drill bit being guided parallel to the layers. As a result, the available borehole length in the deposit is significantly greater, which generally increases the production yield. In high-volume hydraulic fracturing, large amounts of liquid with more than 1000 m³ per fracking phase or a total of more than 10,000 m³ per borehole are used.

Since the late 1940s, fracking has been used primarily in oil and gas production and in the development of deep aquifers for water extraction and to improve heat transport in deep geothermal energy . In the latter cases, no proppants or chemical additives are required. Since the beginning of the 1990s, and especially in the USA from around the year 2000, production by means of fracking has focused on so-called unconventional crude oil and natural gas (including " shale gas "). The fracking boom there changed the US energy market considerably and caused prices to fall. This led to a debate about the viability of the process. The US government has therefore been supporting efforts to increase the export of liquefied natural gas to Europe and Japan since around 2013 , including with accelerated approval processes.

While some voices emphasize this geostrategic component by changing international dependencies, the environmental risks and possible health hazards of the “fracking boom” lead to a controversial and ongoing professional, political and social debate, especially in Europe. Some countries and regions have banned natural gas fracking in their territories.

application areas

Schematic representation of the production of crude oil and natural gas, left: conventional deposits, right: unconventional deposits.

In the first few years after its development, the fracking method was mainly used to extend the production period of a crude oil or natural gas deposit or to reduce the drop in the production rate in the late phase of the exploitation of a deposit. These were so-called conventional reservoirs, with relatively high natural porosity and permeability of the reservoir rock.

Since the 1990s, however, fracking has increasingly been used to extract fossil hydrocarbons from so-called unconventional oil and gas reservoirs with low-porosity and impermeable reservoir rocks, with a distinction being made between primary and secondary reservoirs. In the case of secondary reservoirs , oil and gas have migrated from their host rock into what was once a sufficiently porous and permeable reservoir rock , the porosity and permeability of which has subsequently been significantly reduced, so that a production rate that is too low would be achieved today using conventional production methods. One speaks here of tight oil and tight gas .

More important is the application for extraction from primary deposits, where oil and gas are still in their bedrock. These can either be coal seams (CBM, Coal Bed Methane) or clay stones (shale gas, shale oil). Such mudstones are often incorrectly referred to petrographically as slate , which is partly traditional and partly based on an imprecise translation of the English word shale ("thin-plate claystone"). The gas and oil extracted from these claystones is therefore called shale gas or shale oil. In the case of shale oil, this can lead to ambiguities as to whether “ripe” oil from primary deposits, ie “fracking oil”, is meant, or oil that has been extracted from an “unripe” oil shale .

"Fracken" is based on several horizontal boreholes within the deposits. Each borehole is individually fracked and seismically monitored in order to be able to control the crack propagation via the pressure level. The technique itself dates from the 1940s, and was first used commercially in 1949. Other mining areas have been fracking for a long time. Since the significant price increase for oil and gas, there has been an increasing number of fracking, especially in the USA (more than fifty thousand in 2008 alone). About 90% of all US gas wells are fracked, creating a temporary oversupply of gas that led to a collapse in gas prices there.

Outside of oil and gas production, there is also fracking to stimulate reservoirs, for example to stimulate the flow of water in deep geothermal energy , from groundwater wells for drinking water supply and in mining for solid mineral resources. In some cases, wells for long-term pre - degassing of coal seams are fractured.


Fracking drilling site in the operating state with supply lines

In hydraulic fracturing , a liquid (fracfluid), which can also contain a proppant, is pressed into a hole that is usually several hundred to a maximum of 3000 meters deep. The fluid pressure reached in the area to be fracked must exceed the lowest tension in the rock and the tensile strength of the rock in order to break up the rock. If this is the case, the liquid pushes the rock apart (tensile crack). Normally, the horizontal components of the stress field are smaller than the vertical component, because the vertical component - the lithostatic pressure resulting from the weight of the overlying rock layers - increases continuously with depth and is therefore the largest of the main stress components below a certain depth. For example, fracking causes tensile cracks mainly as almost vertical crack surfaces that open in the direction of the smallest horizontal main stress and thus spread in the direction of the greatest horizontal main stress. On a small scale, the field of tension can e.g. B. be oriented significantly differently due to additional tectonic stresses.

After the formation has broken up, the injection pressure is reduced and most of the injected liquid, which is still under the pressure of the rock layer, flows back for the most part. This backflow water backflow or flowback called. The added proppant remains in the cracks and keeps them open. Also additives of Fracfluids remain partly by adhesion effect of the fluid-rock boundaries in the rock.

In order to optimally convey the dissolved gas, several boreholes, often almost horizontally in depth, but in any case within the target formation, are drilled from a drilling starting point. The deflected boreholes are precisely guided in the deposit with the help of the so-called directional drilling process. The drilling path is controlled with the help of an MWD ( measurement while drilling ) unit placed directly behind the drill bit (geo-steering).

The deflected boreholes are then fractured individually and in sections, adapted to the geological and geomechanical subsurface conditions, several times (12 to 16 times). The aim of this “multi-well pad” method is the spatial exploitation of the gas in the target horizon from a larger volume of the borehole area opened up by the fracs. Only this process enables the breakthrough to large-scale industrial use of frac technology. In contrast, some shale gas fields in the United States and elsewhere, such as the Jonah gas field in Upper Green Valley / Wyoming, were previously developed with individual vertical, undeflected wells. This required six to eight holes per square mile (equivalent to two to three holes per square kilometer). With today's technology, the number of boreholes per square kilometer and, in particular, the number of drilling sites is drastically reduced, with the possible length of the deflected borehole sections determining the drilling site grid. Today, distances of 10 km between the drilling sites are certainly conceivable.


Mixing device for adding the fracturing fluids to the water before it is injected into the borehole.

Frac fluids are liquids that are introduced into the borehole and, at high pressure, create artificial cracks in the gas-bearing target formation. With the help of certain, conditioned fracking fluids, various proppants are introduced into the pathways created by fracking in order to stabilize them for as long as possible and to guarantee gas permeability. A distinction is made between foam-based, gel-based and so-called slickwater fluids. The main component of the highly viscous , gel-based Fracfluide is usually a with additives vergeltes water, the addition mainly tempered sand and ceramic beads (proppant) are added. Gel-based fracturing fluids are mainly used in clastic rocks such as sandstones (conventional deposits).

In contrast, so-called extremely low-viscosity slickwater fluids are mainly used in clay stones (unconventional deposits), which are made extremely flowable by adding friction reducers. Slickwater fluids consist of 98–99% water with 1–1.9% proppants and less than 1% additives.

The composition of the additives is normally disclosed by the drilling and service companies to the supervisory authorities, but is kept secret from the public . In Germany, as part of the drilling approval process, the individual additives must be approved in accordance with the requirements of water law.

Examples of possible additives and the purpose of their use are:

Additive engl. designation Realizations purpose
Proppants Proppant Quartz sand , sintered bauxite , ceramic beads, e.g. B. coated with epoxy or phenolic resin Keeping open and stabilizing the cracks generated during fracking
Gels , thickeners Succeeding agent Guar gum , cellulose polymers, such as. B. MC and carbohydrate derivatives Increase in the viscosity of the fracturing fluid for better proppant transport
Foaming agent Foam CO 2 or N 2 as well as frothers: tertiary alkylamine ethoxylates, coconut betaines or α-olefin sulfonates Transport and storage of the proppant
Deposit inhibitor Scale inhibitor Ammonium chloride , polyacrylates and phosphonates Prevention of deposits and dissolution of poorly soluble mineral deposits in the borehole
Anti-corrosive agents Corrosion inhibitor Methanol , isopropanol , ammonium salts , sulfites , (e.g. amine bisulfite) Protect plant, equipment and the drill string
Chain breaker Breaker Sodium bromate , ammonium and sodium peroxodisulphate , enzymes Reduction of the viscosity of gel-based fracturing fluids for better recovery of the fluids (destruction of the gel structure)
Biocides Biocide Terpenes , glutaraldehyde , isothiazolinones such as chloromethylisothiazolinone Prevention of bacterial growth and biofilms , prevention of hydrogen sulfide formation ( desulfurication )
Fluid loss additives Fluid Loss Additives Conditioner additives with thixotropic properties Reduction of the outflow of the fracturing fluid into the surrounding rock
Friction reducer Friction reducer Latex polymers, polyacrylamide , hydrogenated light petroleum distillates Reduction of the friction within the fluids
pH buffer pH control Acetic acid , fumaric acid , potassium carbonate , borax , sodium acetate , baking soda , sodium carbonate , sodium hydroxide Buffer for adjusting the pH
Tone stabilizers Clay stabilizer Potassium salts , e.g. B. potassium chloride , ammonium salts Prevention and reduction of the swelling of clay minerals
Surfactants (wetting agents) Surfactants ethoxylated alkyl alcohols, nonylphenol ethoxylates Reduction of the surface tension of the fluids to improve the wettability
Acids Acids hydrochloric acid Cleaning the perforated sections of the drill string from cement and drilling fluid
Hydrogen sulfide scavengers H 2 S scavenger aromatic aldehydes Removal of hydrogen sulfide (corrosion protection)
Cross-linkers Crosslinker Triethanolamine , sodium tetraborate , citrus terpenes, zirconyl chloride , borates , organic zirconium complexes Cross-linking of the gelling agents, increasing the viscosity
solvent Solvents Ethylene glycol monobutyl ether , 1-propanol
Temperature stabilizer Temperature stabilizer Sodium thiosulfate Prevention of the decomposition of the gels at great drilling depths
Iron chelators Iron Control Citric acid , ethylenediaminetetraacetate Prevents the precipitation of ferrous minerals in the target formation

The composition of the fracfluids is determined separately for each borehole with the help of decision matrices and / or computer programs and depends on the mineralogical-geological properties of the target horizon and the pressure and temperature conditions prevailing in the deposit.

In contrast, clean fracking describes a new method of fracking in which only water , bauxite sand and starch are to be used.

Flowback and production water

Sign indicating the official approval of a process water extraction point in the northern catchment area of ​​the Susquehanna River (Marcellus Shale Play, Pennsylvania, USA). The maximum allowed water withdrawal per day is given as 6.0 million US gallons , about 23 million liters.
Open pit with mud created from the reflux water, near the well in the Bakken Formation, North Dakota. In Germany, such open pits would not be approved.

The mud fluid that emerges from the surface of the borehole during drilling and fracking for up to about 30 days afterwards is referred to as reflux water (flowback).

The water that is then pumped consists of mud fluid, formation water (groundwater) and any gases dissolved in it and entrained solids and is referred to as production water. About 20 to 50% of the fracturing fluid brought into the depths is returned as reflux water or with the production water and stored at the drilling site until disposal. Storage in open basins, which is common in some places in American gas fields, cannot be approved in Germany. The containers in which the flowback or production water is stored are subject to water law requirements, so that it should be prevented that liquids can seep into the ground.

The flowback and the production water must be treated and processed in several stages before reuse or final disposal. First of all, the solids (cuttings) are separated in hydrocyclone systems on the drilling site and the sludge is disposed of. The liquids that have been largely freed of solids and returned are usually brought to a treatment station by tanker trucks or through pipelines. There, the oil phase, the remaining sludge and filtrate are separated in various tank farms with phase separators and filter systems . The residual water can according to the hydro-chemical properties either be mixed with fresh water and then the mud circulation can be added or in approved Versenksonden in the edge region of previously developed and exploited hydrocarbon deposits pressed are. The light phase separated in these processes is processed further in refineries , the filtrate is disposed of by certified companies.

In addition, various treatment methods, such as UV treatment, membrane filtration , coagulation and evaporation, are used to either reuse the fracfluids or to reduce the amount to be disposed of.

historical development

The first hydraulic fracturing operation was undertaken in 1947 in a conventional reservoir in the Hugoton natural gas field in Grant County, Kansas , to increase the production rate. It was carried out by Stanolind Oil , but has not yet resulted in a significant increase in the production rate. In 1949, the Halliburton Oil Well Cementing Company (Howco) received an exclusive license after the process was patented in the same year. Only three years later hydraulic fracturing was used in the Soviet Union, mainly to complete water injection wells that serve to maintain pressure in oil reservoirs. In the following years, oil wells were increasingly subjected to hydraulic stimulation measures. River sands served as a proppant to keep cracks open. Frac measures have also been carried out in Central Europe since the 1950s. B. in Austria from 1957 or in German oil deposits such. B. in Lingen-Dalum.

Initially, thickened crude oil or kerosene served as frac fluid, from 1953 onwards water was increasingly used as the basis for the frac fluid, to which so-called additives were added, the main task of which was to change the properties of the water so that the proppants are transported into the cracks created could. Sifted sand from rivers was originally used as proppants. Today mainly quartz sand, ceramic balls or corundum are used as proppants.

As early as the mid-1950s, more than 3,000 fracking measures were carried out every month. In the whole of 2008 there were 50,000 worldwide.

The hydraulic fracking process has also been used in natural gas reservoirs in Germany since 1961. The first borehole that was subjected to such a measure was the "Rehden 15" borehole. Initially, until the end of the 1970s / beginning of the 1980s, only a few frac measures were carried out in natural gas wells in Germany. From then on there was an increase until it peaked in 2008 with nearly 30 hydraulic well treatments performed. Since 2011, despite ongoing applications, no more fracking measures have been approved due to the ongoing, controversial debate. The “Buchhorst T12” well was fractured for the last time so far.

Fracking only became economical thanks to new techniques a few years ago. In the Bakken Formation in the US states of North Dakota and Montana alone, fracking increased daily production from 0 to around 500,000 barrels of oil between 2006 and 2012 . This corresponds to around a third of Libya's funding quota. North Dakota is already producing more oil than Alaska, and the trend is rising.

The new fracking technologies, summarized under the name of superfracking , are being promoted primarily by the industry leaders Baker Hughes , Schlumberger and Halliburton . The key to success were new techniques such as RapidFrac for horizontal drilling in depth, HiWAY , a process that prevents the permeability of the fractured rock from decreasing over time (“ infinite fracture conductivity ”), and DirectConnect , a controlled technique Expansion of cracks with explosions or the rapid melting of the rock using a blasting technique instead of conventional drill heads.

Calibrating the optimal mix of water, sand, proppant, and other chemical lubricants took several decades until 1998 when Nick Steinsberger and other engineers at Mitchell Energy developed a technique called slickwater fracking .

Economic efficiency in the context of natural gas and oil production

In contrast to conventional production, in which crude oil and natural gas are extracted from permeable rock, production from dense (impermeable) rock by means of hydraulic fracturing is limited to the immediate vicinity of the horizontal borehole in the rock. As a result, the production rate of a borehole drops faster than with conventional reservoirs. According to the Federal Institute for Geosciences and Natural Resources , a borehole is 90% extracted after a maximum of two years. In order to achieve quantities comparable to those of a conventional deposit, a higher number of boreholes per area and unit of time is necessary. This may require several hundred wells a year, each costing three to ten million dollars. As a result, unconventional hydrocarbons tend to be more expensive to extract than conventional hydrocarbons, but at least in the US and at least for natural gas, production costs (including exploration and development) between US $ 2 and US $ 4 per 1000 cubic feet (5.19 to 10 , 38 euros per megawatt hour , at a dollar exchange rate of 1.30 euros) quite competitive. For shale oil, they should be around $ 15 to $ 20 a barrel.

Development of the gas price in the USA 2001–2018

A decline in the price of natural gas on the US market, which began in 2008 and ended in a record low in 2012, led to increasing numbers of investors withdrawing from fracking projects and the investment volume from $ 35 billion (2011) to $ 7 billion (2012) and most recently shrank to $ 3.4 billion (2013). US economists also warn against a systematic overestimation of the reserves of unconventional fossil hydrocarbons. In May 2014, the US Department of Energy's statistics department , the Energy Information Administration (EIA), corrected a 2011 estimate of the productivity of what is believed to be the most important shale oil deposit in the USA - the so-called Monterey shale in California - down by 96%. This corresponds to a two-thirds reduction in the estimated US shale oil reserves. Falling prices and disappointed expectations forced several companies to write off billion-dollar investments in unconventional funding projects in 2013. The low gas prices and a fall in oil prices that began again at the end of 2014 are having an impact on smaller companies in particular. If they can no longer service their loans (the total debt burden of the US fracking industry grew by 55% to around $ 200 billion from 2010 to the beginning of 2015) because their production facilities are not working economically, they have to file for bankruptcy. The boom in the first decade of the 21st century was now followed by a phase of market shakeout , although the oil price recovered in 2016 and reached new highs of up to US $ 85 in 2018.

Due to the lockdown-induced global economic crisis in the wake of the COVID-19 pandemic and the associated drastic drop in oil prices, US energy companies specializing in fracking came under severe financial pressure in March 2020. The general throttling of world production, which was achieved in April through an agreement within OPEC + ( OPEC plus major oil producing countries outside OPEC, especially Russia), which was extended at the beginning of June, led to a significant recovery in the market. However, since April 2020 there have been a number of bankruptcies, including those of larger US energy companies, including Chesapeake Energy , which is considered a pioneer in fracking .

In Europe, the costs and thus the threshold value for an economically sensible extraction of unconventional natural gas are higher than in the USA, among other things due to more complicated geological conditions, as well as the generally higher drilling and water costs. In 2010, the production costs for 1000 cubic feet of unconventional natural gas in the North German-Polish lowlands were given as 8 to 16 US $ (corresponds to 20.75 to 41.50 euros per megawatt hour). According to the results of an expert survey carried out by the Center for European Economic Research in 2013 , a significant increase in the production of unconventional natural gas in Europe is only expected at a stable wholesale price of at least 30 euros per megawatt hour. Almost a fifth of the respondents even saw the threshold at 60 euros.

Geostrategic importance

Number of active oil derricks in the US since 1988

For the USA , fracking is of particular geostrategic importance, as it increases independence from fossil hydrocarbons (HC) from the Arab region. This could lead to the United States becoming less involved in security policy in the Near and Middle East, and other states that are still dependent on oil and gas from this region, in particular the European Union and China , have to become more involved. However, because the USA no longer imports any strategically important quantities from the Middle East as a result of the oil crisis in the 1970s and the effects of the "shale revolution" have so far been limited to the natural gas market, it is currently disputed whether such a scenario will actually occur , especially since the US has no interest in increasing Chinese influence in the region.

Venezuela's President Nicolás Maduro accused the US in 2014 of using shale oil production as a weapon in an “oil war” against Venezuela and Russia . The national budgets , and thus indirectly also the political stability, of these two countries are dependent on the oil price , which, according to Maduro, has fallen significantly as a result of the "flooding of the market" with US shale oil. According to its energy authority EIA, the USA has been the world's largest producer of oil since 2013.

As part of the economic sanctions against Russia due to the crisis in Ukraine from February 2014, liquefied natural gas (LNG) from the US shale gas production was emphatically used by US politicians and Chancellor Angela Merkel as an alternative to Russian natural gas for the energy supply of the states of the European Union brought into play. In addition, in the course of the crisis, calls were made for an increased development of unconventional hydrocarbon storage sites in European countries with the help of fracking.

Potential environmental damage and hazards

Schematic representation of the potential environmental risks of a well


In general, all drilling techniques involve certain environmental risks, especially when they are related to the extraction of fossil hydrocarbons. However, these risks are increased in fracking for the production of shale oil and gas due to the high number and density of wells and drilling rigs on the one hand and on the other hand there are additional risks because the fracfluid chemicals, etc. a. Biocides. Risks in the production of crude oil and natural gas by means of fracking exist in detail with regard to:

  • contamination of the near-surface groundwater used for drinking water abstraction with fracking fluids and the chemicals contained therein through leaks in the piping
  • a contamination of surface water by the fracking fluids (the so-called backflow ) and the chemicals they contain, which emerge at the upper end of the well after the fracking process
  • Migration of substances from the deposit to other layers
  • Accidents during the removal of the process water plus the chemicals it contains
  • Vibrations during drilling and regular fracking

In addition, critics fear that in addition to the intended microquakes , larger earthquakes will also be triggered. Noticeable tremors that occurred immediately during a "frack job" have been reported in individual cases so far, the damage caused by this is not known. The probability of stronger earthquakes (magnitude> 4.0) is assessed by experts as very low, because earthquakes can only be triggered where the rock is already under increased mechanical tension (regardless of fracking) . However, due to the large water volumes, which are thereby introduced into the ground, which has compression of fracking wastewater (Engl. Deep injection to the effect a higher risk potential) as the fracking itself. In the immediate vicinity of such Verpressungsanlagen are in the USA a few Earthquakes with a magnitude> 5.0 were registered, which also caused minor damage. In view of the more than 140,000 wells in the USA used for oil and gas fracking as well as for fracking wastewater injection, the number of seismic events with magnitudes> 4.0 (see below ) that have been directly or indirectly related to fracking is negligible .

Pollution of water and soil

Söhlingen gas well (Lower Saxony)
Söhlingen gas well
Söhlingen gas well
Söhlingen gas well on the map of Lower Saxony
Use of water in fracking

In hydraulic fracturing for the purpose of extracting unconventional fossil hydrocarbons, 3 to 12 different chemicals (including biocides) are injected into the borehole, usually around 10 million liters of water and quartz sand, with a total proportion of 0.5 to 2 percent by volume . The large volumes of the pressed-in fracturing fluids lead to a correspondingly large absolute amount of chemicals. For example, a US Congress study found that between 2005 and 2009 a total of 43 million liters of chemicals were used. The effects on the environment are controversially discussed in public and criticized by water suppliers in Germany, because some of the chemicals used are toxic or, according to the German Hazardous Substances Ordinance, carcinogenic , poisonous or otherwise harmful to health.

In the states of Colorado, North Dakota, Pennsylvania and New Mexico, between 2005 and 2014 more than 6,600 above-ground leakages and spills of varying sizes were reported at drilling sites for the development of unconventional oil and gas reservoirs with a total of almost 31,500 wells. Between two and 16 percent of the plants have released potentially environmentally harmful liquids into the environment at least once a year. Depending on the state, events with at least 42 to 120 gallons (approx. 160 to 450 liters) of leaked liquid were notifiable. Around half of the leaks occurred through tanks and pipelines - only a relatively small proportion during the actual drilling and fracking activities. Follow-up examinations of such events showed that in 50% of the cases after removal of the superficial pollution, BTEX was detectable in the near-surface groundwater in concentrations above the limit values. In Germany, too, fracking wastewater ended up in the environment. For example, authorities and ExxonMobil stated that in 2007 there was contamination with BTEX in the Söhlingen gas field due to leaky wastewater pipelines. In the USA, wastewater that was inadequately treated was also discharged into surface waters.

A further problem is considered that residues of the fracturing fluids are deposited in the cracks. In the case of some additives (e.g. frac sands) this is even wanted because they keep the cracks open. Although around half of the liquid used, the so-called produced water , is pumped back to the surface, the influence of the remaining water has not been conclusively clarified and is currently being reassessed by the American Environmental Protection Agency (EPA) .

In the USA in particular, the possible contamination of groundwater by natural gas in direct connection with hydraulic fracturing has been the subject of controversial discussion. The controversial documentary Gasland from 2010 deals in detail with this topic. Among other things, it is shown that the concentration of the gas in the groundwater can be so high that it can be ignited with a lighter on an open tap. The causal connection with shale gas production is controversial, since natural gas can also find its way into aquifers close to the surface naturally . Studies conducted by Duke University in the “Marcellus Basin” ( New York and Pennsylvania ) have shown that drinking water wells in the vicinity of shale gas production wells can have increased exposure to methane, ethane and propane (so-called stray gas ). The scientists took samples from 68 and 141 private wells, respectively. Although methane was found in more than 80% of the samples, regardless of whether shale gas production activities were taking place in the vicinity or not, the methane pollution in wells within a maximum radius of one kilometer from a shale gas well was an average of 17 or six times the ethane concentration even twenty-three times higher than in other wells. Propane was also detected in the water of ten such wells. The presence of ethane and propane in the samples as well as the carbon isotope signature of methane indicated that the heavy impurities are clearly due to natural gas. According to the studies, the most likely cause of the contamination is gas leakage through leaks in the casing and annulus cement of the wells. However, such a disruption would not be fracking-specific, but can also occur when natural gas is extracted from conventional reservoirs. In the Barnett Shale production region in Texas, increased concentrations of arsenic , selenium and strontium have been detected in drinking water wells located within a radius of no more than 2 km from a drilling site .

According to the Public Herald, a Pennsylvania nonprofit, nearly 9,500 complaints from residents of shale gas drilling sites were received by the state's Environmental Protection Agency (DEP) between 2004 and 2016, with the number of annual complaints correlating with the number of annual shale gas drilling. Over 4,100 complaints related to suspected contamination of near-surface groundwater used by residents as drinking water. What is particularly explosive here is that these figures were initially not published by the DEP, and that the authority is said to have not dealt with a certain number of the complaints according to regulations.

Greenhouse gas immission

If the two-degree target for global warming is to be met with a probability of 50%, according to data from the IPCC, a maximum of between 870 and 1,240 gigatons (billion tons) of carbon dioxide may be released in the period from 2011 to 2050 . This requires a significant reduction in greenhouse gas emissions compared to the status quo, which in turn drastically restrict the use of fossil fuels requires. Converted to the global reserves, this means that in the global context, among other things, around a third of the oil reserves , half of the natural gas reserves and more than 80% of the coal reserves may not be burned.

While fracking to improve the pathways in the rock with deep geothermal energy helps to reduce the consumption of fossil fuels and thus reduce greenhouse gas emissions, the extraction of fossil hydrocarbons and their combustion naturally cause high net greenhouse gas emissions. Most of the greenhouse gas surplus from unconventional natural gas production is partly due to carbon dioxide emissions, but partly also to methane emissions . The carbon dioxide comes mainly from the combustion of the extracted gas by the end user and from the combustion of other fossil fuels in connection with the extraction of the gas. Methane, on the other hand, escapes as the main component of the unburned raw gas from conveyor systems (e.g. via pressure relief valves) and leaks in transport pipelines.

Since methane is considered to be a much more effective greenhouse gas than carbon dioxide, methane emissions are the main contributor to the greenhouse gas surplus. While the venting of gas from pressure relief valves and the escape from pipelines during the actual production occur equally in conventional (i.e. non-fracked) and unconventional natural gas reservoirs, the methane emissions are said to occur in the development of an unconventional reservoir, i.e. H. in the phase in which mainly fracking takes place, about 20 times higher than when a conventional deposit is developed. The methane escapes mainly during the flowback exit following a fracking process and during the so-called drill out at the beginning of the actual production, the drilling of closures in the horizontal conveying pipe that had previously sealed off the individually fracked sections from one another. In addition, methane can escape during so-called liquids unloading . This is a measure by which condensation water is removed which has accumulated in the course of production at the lower end of the borehole as a result of decreasing reservoir pressure, which has a negative effect on the production rate. To do this, the borehole is closed for a while ( shut-in ) so that the reservoir pressure can build up again. Then the bore is opened to the atmosphere so that the now relatively high pressure drives the water upwards out of the bore ( well blowdown ). This method also releases gas and thus methane into the atmosphere. However, liquids unloading is less necessary for unconventional pumping than for conventional pumping. Overall, methane emissions can account for up to 10% of total production from a single unconventional well.

The exact greenhouse gas balance of unconventional hydrocarbon extraction by means of fracking has so far been relatively little researched, and the assessments of the greenhouse gas balance of unconventional hydrocarbons compared to other fossil fuels are contradictory. The greenhouse gas balance of unconventional natural gas compared with that of coal , the “most harmful to the climate” among conventional energy sources, is particularly controversial . Some of the researchers come to the conclusion that replacing coal with fracking natural gas would lead to a reduction in greenhouse gas emissions and that this would be less “climate-damaging” than coal. Based on such calculations, the unconventional hydrocarbon production is often declared as a bridging technology that is intended to temporarily replace the use of coal before energy is largely generated from renewable sources in the future . However, other researchers are not predicting an effective reduction in greenhouse gas emissions, or the energy carrier unconventional natural gas is said to have a worse greenhouse gas balance than the energy carrier coal.

In the specific case of electricity generation from shale gas of the Marcellus Formation in base load power plants , it is estimated that greenhouse gas emissions are only 3% higher than with conventional natural gas produced in the USA, but up to 50% lower than with electricity generation from coal. Another study comes to the conclusion that, due to the high methane emissions, especially when developing the reservoirs, unconventionally extracted natural gas has a worse greenhouse gas balance than coal even with a conservative estimate and is only less “climate-damaging” if the extraction phase per drilling site is unrealistically long “Is. According to the assessment of the German Federal Environment Agency, there is a lack of more precise empirical data for a precise assessment, in particular with regard to methane emissions.


Fracking inevitably leads to "earthquakes", but these are microquakes whose magnitude is usually less than 1.0, because the changes in the stress conditions in the affected rock caused by the pressure of the fracking fluid are relatively small and within a few kilometers limited to the hole. If special geological conditions are met, tensions in the rock that have existed for geological time periods can be released during a fracking process, which can lead to earthquake swarms with individual, significantly stronger vibrations. In such cases, anomalous seismic events are also spoken of. In many regions of North America where fossil hydrocarbons are extracted, seismic activity has increased dramatically in the wake of the fracking boom. In the US state of Oklahoma it is currently (as of 2015) even higher than in California, the US state that is crossed by the San Andreas Fault . However, this does not say anything about the probability of occurrence of severe or very severe earthquakes, as they have already occurred in California. The strongest earthquake to date, which was probably triggered in the course of a fracking process, occurred on January 22, 2015 in Fox Creek in the Canadian province of Alberta with a magnitude of 4.4. Also in Canada, in the Horn River Basin in the northeast of the province of British Columbia , numerous seismic events with local magnitudes (M L ) above 2.0 were recorded between April 2009 and December 2011 . However, only the strongest quake was clearly noticeable with M L 3.8 ( moment magnitude M W 3.6). The remaining 8,000 or more high volume fracking operations carried out in northeast British Columbia by 2012 did not result in any anomalous seismic activity. Also worth mentioning is an earthquake swarm in the Poland Township near Youngstown in March 2014, the five strongest quakes with magnitudes between 2.1 and 3.0. The most noticeable seismic events in Europe to date consist of two tremors with magnitude 2.3 and 2.9 on April 1, 2011 and August 26, 2019, respectively, immediately east of Blackpool . The shock in August 2019 is said to have been noticeable in Preston, about 10 kilometers away . As a result of this event, the UK Department of Energy issued a shale gas fracking moratorium in November 2019, which is valid until further notice.

After more or less intensive treatment, fracking wastewater is disposed of in rock layers deep underground. In this so-called compression , sometimes enormous volumes of liquid are pumped into the corresponding target horizon. Here, too, there is a risk of earthquakes being triggered under certain geological conditions. The strongest earthquakes that have occurred so far in connection with fracking are partly presumed, partly verifiable, due to wastewater injection.

The anomalous seismic events during fracking and the earthquakes occurring in the course of wastewater injection are explained by the fact that the increasing pressure as a result of the injection of fluids in the pore space of a water-saturated, pre-tensioned (seismogenic) rock to a nearby one, appropriately in the regional field of tension oriented fault " puffs through " ( pore pressure diffusion ). This reduces the static friction on the fault surfaces, which can lead to movements taking place at the fault. These manifest themselves in the form of a swarm of earthquakes with individual vibrations, which can sometimes be significantly stronger than a microquake. There is a connection between the strength of such a triggered tremor and the volume of the injected fluid. When grouting, significantly larger volumes are brought into the subsoil than when fracking. These also remain permanently in the subsurface and the corresponding target horizon has a high conductivity for fluids ( permeability ). In the case of fracking, on the other hand, the target horizon has a low conductivity and a not insignificant part of the injected fluids emerges again at the upper end of the borehole after completion of a fracking measure ( backflow ). For these reasons, the probability of a stronger earthquake and its maximum achievable magnitude is higher with wastewater injection than with actual fracking.

Map of the region around Guy and Greenbrier, Arkansas, showing the epicentres and magnitudes of the so-called Guy-Greenbrier earthquake swarm 2010/11.

In fact, of the five seismic events recorded east of the Rocky Mountains in 2011 with major earthquakes with a moment magnitude of 4.0 or more and which were demonstrably related to hydrocarbon production, two were relatively certain and one likely to the injection of wastewater : For example, a series of stronger quakes in the Guy Greenbrier Fault in the US state of Arkansas , unknown until autumn 2010 , of which one (February 27) reached M W 4.7, led to a moratorium, which u. a. the drilling of new boreholes for the injection of sewage in the area of ​​the Guy Greenbrier fault is permanently prohibited. On August 23, an earthquake with M W 5.3 occurred near Trinidad in the Raton Basin in the south of the US state of Colorado . It was the strongest of a whole series of noticeable earthquakes that had occurred since 2001 in what had been the seismically inconspicuous region up to New Mexico . The likely trigger is the injection of large volumes of wastewater from the CBM production carried out there since 2001. The strongest series of earthquakes occurred in November near Prague in the Wilzetta oil fields in the US state of Oklahoma . Three of their earthquakes reached M W ≥ 5.0 and the strongest (6 November) even M W 5.7. So far (as of 2015) it was the worst earthquake ever recorded in Oklahoma with instruments and the worst that has so far occurred in the wake of injected sewage. It destroyed two single-family houses and damaged other buildings. Two people were injured. On December 30th, the “Northstar I” injection plant near Youngstown in Ohio had to be shut down after a tremor with an M W 2.7 could be directly attributed to its operation. A day later there was even a noticeable quake, which at 3.9 was just below the moment magnitude of 4.0. The injected wastewater came from the hydrocarbon production in the Marcellus Shale in neighboring Pennsylvania .

Health risks

Health risks from fracking arise primarily in connection with the extraction of fossil hydrocarbons. In various countries, possible and in some cases already known risks of hydrocarbon fracking are being discussed from a medical point of view.

Hazards that are closely linked to hydrocarbon fracking arise from the contamination of ground and surface water with fracking fluids or the additives they contain. With around 100 of the total of 750 additives used is known or suspected so-called endocrine disruptors (Engl. Endocrine disrupting chemicals , EDC), the human sex hormone disturb household. EDC with an estrogen-like effect are considered to be the cause of infertility and cancer. EDC, which block the docking points for male sex hormones (anti-androgenic EDC), can cause malformations of the male genitalia and infertility. Research by the University of Missouri, Columbia, in a region with a high density of unconventional natural gas production facilities in Garfield County , Colorado, found that EDC from fracturing fluids was detectable in the region's groundwater and surface water.

In addition, there are health hazards that are not or only partially specific to fracking, for example the unwanted conveyance of radioactive material from the storage sites (see also →  Radioactive waste from oil production ). On the other hand, the possible release of lung cancer-causing radon from unconventional deposits seems to be specific to fracking , which then migrates through the outer layers into the cellars and lower floors of houses. In a study carried out in the US state of Pennsylvania , which statistically evaluated measured values ​​from 763,000 buildings in the period from 1987 to 2013, the shale gas production in the Marcellus Shale was determined as one of several factors for an increased indoor air radon concentration: From 2004, Coinciding with a steady increase in shale gas production in the state, the radon concentrations in counties with a high number of production plants or a high shale gas production rate were statistically clearly higher than the concentrations in counties with low shale gas production. In Pennsylvania, however, the indoor air is generally significantly more polluted with radon than in other US states due to the regional geological conditions. There are clear differences here between large cities and rural regions. In Philadelphia , Pennsylvania's largest city, by far the lowest radon concentrations were measured. They were still well below the concentrations measured in counties with little or no shale gas extraction. In counties through which the so-called Reading Prong runs, a geological province of the Appalachian Mountains rich in gneiss , the concentrations were by far the highest in the entire measurement period, much higher than in counties with high shale gas production. The differences between Philadelphia and counties with low shale gas production or Reading-Prong counties and counties with high shale gas production were always greater than the differences between counties with low and counties with high shale gas production throughout the measurement period.

Also is not pure frackingspezifisch the contamination of air and groundwater with so-called BTEX aromatics, especially with the blood and bone marrow carcinogenic applicable benzene . They are contained in small amounts in conventional and unconventional fossil hydrocarbons and reservoir water. With fracking, however, the backflow also adds contaminated water. If this water is stored in open tanks (prohibited in Germany), BTEX aromatics and other harmful hydrocarbon compounds can escape into the air. Based on concentrations of air pollutants (including emissions from internal combustion engines of trucks and diesel generators) that have been around tight gas handling systems in Garfield County, Colorado, measured, calculated, a research group of the Colorado School of Public Health of the University of Colorado in Aurora that Residents less than half a mile (around 800 m) away from the conveyor system are exposed to a significantly higher risk of developing cancer and chronic non-cancer diseases than residents more than half a mile away. The non-profit network for environmental patients (GENUK) suspects, due to the carcinogenic effects of benzene, that this substance is the cause of a statistically significant increase in the number of "new cancer diseases of the lymphatic, hematopoietic and related tissue" in older men in the Rotenburg / Wümme district in Lower Saxony Period 2003 to 2012 is. The district is one of the centers of onshore natural gas production in Germany, including the production of tight gas, and contamination there with BTEX-containing reservoir water from leaking pipelines is documented for at least 2012. As part of two studies, one conducted in rural Colorado with almost 125,000 participants between 1996 and 2005, and the other in southwestern Pennsylvania with almost 15,500 participants between 2007 and 2010, they examined the number of unconventional natural gas production facilities in the vicinity of the home the mother or the distance from the home to these conveyor systems had an impact on the health of a newborn (the closer and / or more conveyor systems, the greater the exposure ) Neither study found an increased number of premature births in more exposed mothers. The results regarding the birth weight for term births contradicted each other. Pennsylvania also found that high exposure increases the likelihood that a newborn will be too small for its age (not studied in Colorado). The Colorado study found an increase in the number of congenital heart defects with increasing exposure and a (significantly) increased number of neural tube defects only with high exposure ( not investigated in Pennsylvania). The authors of both studies emphasize that their informative value is limited and further research is necessary.

If, as a result of the increased use of fracking, the extraction of fossil hydrocarbons spreads rapidly in relatively densely populated regions, this inevitably increases the associated (potential) pollution and consequently the health risk for the local population. Ultimately, it does not matter whether the pollutant emissions are specific to the unconventional extraction of fossil hydrocarbons by means of fracking, or whether they also occur with conventional extraction. Ultimately, it is crucial that they occur and that they would not occur without the use of fracking, provided that only unconventional production is possible in the regions concerned.

Hydraulic fracturing worldwide

Fracking became really widespread in the 1950s. For crude oil and natural gas, the main area of ​​application for fracking, there were 2.5 million frackings up to 2012. Including over a million times in the USA.


In terms of production volumes, the use of fracking is much more widespread in North America than in South America .

United States

“Fracking is harmful to health” - banner at the “Clean Energy March” in Philadelphia (July 24, 2016).

The USA is considered a pioneer in the use of fracking technology in the extraction of unconventional fossil hydrocarbons (shale gas, etc.). In the course of the first decade of the 21st century, numerous unconventional oil and gas fields were developed there in a real boom. The most important target formations for production include the Marcellus Shale (Central Devonian) in Pennsylvania, the Niobrara Shale (Upper Cretaceous) in Colorado and Wyoming, the Barnett Shale (Lower Carboniferous) in Texas, the New Albany Shale (mainly Upper Devonian) in Illinois, the Bakken Shale (Upper Devonian-Lower Carboniferous) in Montana and North Dakota and the Monterey Shale (Miocene) in California. Supplying the US market with, in particular, unconventional natural gas led to falling prices and a reduction in imports. With the global economic crisis from 2007 onwards, however, demand fell, prices continued to fall and the boom ebbed significantly. In the second half of 2015, due to the falling oil price, shale oil production fell by more than 400,000 barrels per day, but the number of tailcoats increased at the same time.

In the course of the massive expansion of the production of unconventional crude oil and natural gas by means of fracking, there were increasing voices pointing out the risks of this technology for the environment and health. This led to a heated controversy that spread to other industrialized countries. In the state of New York, for example, there has been an official ban on fracking for hydrocarbon extraction since December 12, 2014, as has been the case in Vermont since 2012 .


Fracking has been actively used in Canada since at least the 1960s. A hotspot here was the Alberta region in particular , where gas was extracted from the Spirit River Formation in the late 1970s . The social debate continued amplifies an in July 2011, when the Executive Council of British Columbia the company Talisman Energy a twenty-year license to extract water from the Williston Lake granted. A fracking moratorium has been in place in the province of Québec since 2014 .


In Colombia , fracking has been used for several decades to exploit conventional oil deposits. Due to the increasing depletion of these deposits, however, the Colombian government is considering granting concessions for the development and production of unconventional oil deposits by means of fracking under strict conditions. This is criticized by environmentalists.


South Africa

Map of concessions in the Karoo Basin

Fracking has been used in South Africa for decades to increase the yield from wells, including drinking water wells. As a result of a broad public discussion, a moratorium on fracking for the extraction of shale gas was imposed in 2011. In 2012 the moratorium was lifted again. This was justified on the one hand with the creation of new jobs, on the other hand, shale gas is cited by the South African government as a bridging technology for the transition from coal to other energy sources. Three companies received licenses to exploit the shale gas deposits on around 20% of the area of ​​South Africa. It is estimated that the supplies in the Karoo are sufficient to supply South Africa for 400 years.



In China, a shale gas source was first developed using fracking in 2011. According to a study by the EIA, China is expected to have the largest shale gas reserves in the world, outperforming those of the US by half.


In October 2013 the European Parliament voted for a binding environmental impact assessment for shale gas drilling. In January 2014, the EU Commission presented non-binding recommendations according to which environmental impacts should be examined and avoided. The implementation is left to the individual member states.

On February 27, 2015, the EU Commission published the results of its survey of the Union countries on their plans and projects relating to high-volume hydraulic fracturing.


Areas with shale gas potential in Germany (in orange). Currently, however, the focus is only on the Northwest German Basin (Lower Saxony, Westphalia), the Molasse Basin (Bavaria, Baden-Württemberg) and the Upper Rhine Rift (Baden-Württemberg).

Hydraulic fracturing has been used in Germany since 1961, in particular to increase or keep the production rates constant in conventional oil and natural gas production as well as for drinking water extraction, for remediation of contaminated sites and for geothermal drilling ("stimulation"). Around 300 tailcoat jobs have been carried out nationwide, most of them in Lower Saxony . Initially, only vertical drilling was used for fracking; For the first time in a horizontal well, fracking was used in Germany in the Söhlingen Z10 well in 1994. Commercial extraction of crude oil and natural gas from shale did not take place in Germany.

Social debate

Hydraulic fracturing has been the subject of controversial discussion both in Germany and at European level for several years. The criticism is mainly based on experiences from the USA or films like Gasland . In Germany, resistance is often formed in citizens' initiatives . Various funding companies, such as ExxonMobil, tried proactively to influence the discussion, to collect concerns in an information and dialogue process and to have them clarified by an expert group of independent scientists. Business representatives tend to be for or against fracking, depending on the branch of industry.

In particular, the environmental risks of fracking are controversial. For better classification, the German Research Center for Geosciences (GFZ), the Federal Environment Agency , the Advisory Council for Environmental Issues and the Federal Institute for Geosciences and Natural Resources (BGR) prepared much-discussed expert reports on the effects between 2010 and 2015. All of the reports came to the conclusion, with varying emphasis, that on the one hand the current data situation is insufficient for a final assessment of the possibilities and risks and on the other hand that the legal framework is not clearly defined both in the approval process and in the subsequent monitoring process. It was suggested to improve the data situation by means of controlled, transparent and step-by-step pilot drilling and other investigations and to create the legal framework, in particular for the aspect of environmental requirements. The economic profitability of the development of shale gas stocks in Germany was also critically discussed in the reports.

Legal situation

After a development process that lasted more than three years and was accompanied by numerous controversies with the participation of two federal governments, the law amending water and nature conservation regulations on the prohibition and risk minimization of fracking technology procedures ( Federal Law Gazette I p. 1972 ), commonly referred to as the "Fracking Act", passed. This article law , which includes changes in particular to the Water Resources Act and the Federal Nature Conservation Act , introduces a general ban on fracking in unconventional deposits ( shale gas , coal seam gas ). Tight gas fracking, which has been practiced for a long time in deep layers of dense sandstone, remains permitted, except in sensitive areas such as those that are important for the drinking water supply. As an exception to the fracking ban in unconventional storage sites, a total of four tests for scientific purposes are permitted nationwide - the federal states concerned must, however, expressly consent to these. An independent commission of experts is to report on the knowledge gained by 2021. In the same year, the Bundestag is to review “on the basis of the current state of science and technology” whether the fracking ban should be relaxed or finally cemented.


The Montanuniversität Leoben , together with the oil and gas group OMV, developed a pilot project in the Austrian Weinviertel in which so-called clean fracking was to be used. In clean fracking, only water, bauxite sand and starch are used as proppants. Drill cores should be obtained through test drilling in order to confirm the feasibility of clean fracking based on the geomechanical properties of the cores. It has been suggested that the method is more environmentally friendly but less economically efficient. In 2012 the project was discontinued due to inefficiency.

The test drillings in the Weinviertel were planned in the regions around the city of Poysdorf and the village of Herrnbaumgarten . Due to public protests, the political decision-makers have denied OMV the test drillings on the ground through the media. This was followed by anchoring a mandatory environmental impact assessment for shale gas drilling. A citizens' initiative was formed in Austria to point out the dangers of shale gas fracking.


In Switzerland, the use of the subsoil is subject to cantonal sovereignty. The corresponding legal bases partly date from the 19th century. The canton of Aargau recently introduced a permit requirement for exploration or use of the deep underground. The Canton of Lucerne is planning to introduce a similar regulation. The eastern and central Swiss cantons of Appenzell Innerrhoden, Appenzell Ausserrhoden, Glarus, St. Gallen, Schaffhausen, Schwyz, Thurgau, Zug and Zurich are working together on a legal basis. The French-speaking cantons of Friborg and Vaud have set a moratorium on gas exploration and extraction. In the canton of Bern gas explorations were between Aarberg and Biel granted.


After the granting of four drilling permits for shale gas extraction on a total area of ​​9,672 km² in March 2010, the flaring public debate led in July 2011 to a ban on exploring and extracting shale gas with the help of hydraulic fracturing on the French mainland for non-scientific purposes. Companies that wanted to use fracking to extract shale gas were withdrawn shortly thereafter. This was also confirmed by the French Constitutional Court in October 2013 . Shortly before, President François Hollande had once again confirmed that a permit for shale gas mining in France was not to be expected during his term of office.


French oil companies are moving abroad because of the attitude of their government. Total received a state license for test drilling in Denmark , which was carried out at Dybvad in 2015 . Shale gas deposits here are limited to the north of Jutland and their exploitation is currently not very profitable.

Other states

Within the EU, Poland in particular had planned to intensify the production of unconventional gas and in July 2013 had already awarded around 100 fracking concessions. However, due to an investment climate that energy companies perceived as unsafe and the relatively complicated geology of the reservoirs, shale gas exploration activities in Poland actually came to a standstill at the end of 2017.

Bulgaria banned shale gas production using fracking in 2012 and withdrew a license that had already been granted to Chevron .

Following a major seismic event in the area of ​​the fracking facility near Blackpool in August 2019, the UK government imposed, based on a report from the UK Oil and Gas Authority (OGA), that "unacceptable Consequences "for residents of such facilities could not be ruled out, in November 2019 a nationwide fracking ban.



In Australia , hydraulic stimulation was mainly used for extraction from conventional deposits until the mid-2000s. This practice was particularly widespread in the Cooper Basin . Shale gas occurs particularly in Western Australia in the Canning Basin. These deposits are currently in the exploration phase. The start of commercial production on a large scale is expected between 2020 and 2025.

As in the USA, regulation of the use of fracking to extract unconventional hydrocarbons is a matter for the states, and in Australia, too, there is a social debate about the risks and opportunities associated with this technology. The fracking opponents were able to record some successes here. In the state of Victoria, for example, a moratorium was imposed in 2012 that was still in force in 2014. In the state of New South Wales , BTEX aromatics were banned as additives in coal seam gas extraction that same year .

New Zealand

In the Taranaki region in New Zealand , gas has been extracted using fracking since 1993. The technology is currently mainly regulated by the Resource Management Act of 1991. Protests by environmentalists resulted in four local governments imposing a moratorium in 2012, but a nationwide moratorium was rejected by the government. A study commissioned by the Parliamentary Commissioner for the Environment came to the conclusion in an interim report that the regulation must be tightened.


Web links

Wiktionary: Fracking  - explanations of meanings, word origins, synonyms, translations
Commons : Hydraulic Fracturing  - Collection of Images, Videos and Audio Files


Background reports

Videos and reports

Individual evidence

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