SHALE GAS ROBERT HACK FACULTY OF GEO-INFORMATION SCIENCE AND EARTH OBSERVATION (ITC), UNIVERSITY OF TWENTE, THE NETHERLANDS. PHONE:+31 (0)6 24505442; EMAIL:
[email protected]
UNIVERSITY TWENTE, The Netherlands; 13 May 2014
SHALE GAS What is shale gas? Why is it different from conventional gas? Why exploitation? Potential in the Netherlands Shale gas exploitation by fracking Possible hazards Water pollution chemicals used to free gas underground on surface Earth tremors by fracking by releasing (virgin) stress Societal consequences Nuisance due to making boreholes References Shale Gas - Hack
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WHAT IS NATURAL GAS? Natural gas consists mainly of: methane (CH4) and normally, it also includes heavier hydrocarbons, such as: ethane (C2H6) propane (C3H8) butane (C4H10) and usually some non-hydrocarbon admixtures (e.g. carbon dioxide (CO2), nitrogen (N2), and hydrogen sulfide (H2S))
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WHAT IS NATURAL GAS?(2)
Natural gas originates mainly from decay of (deeply) buried organic material (e.g. remains of plants, animals) over thousands to millions of years, and some limited sources may be of non-organic origin (e.g. volcanic) (In the Netherlands decay of peat is a main source of shallow natural gas, which in
the past, was sometimes exploited by farmers for heating and light)
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WHAT IS NATURAL GAS?(3)
Gas may stay in the geological formation where formed, or may migrate to and be trapped in a different formation, or may leak up to the Earth surface and mix with the Earth atmosphere
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WHAT IS NATURAL GAS?(4)
Gas fields are differentiated in: Conventional gas and Unconventional gas
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WHAT IS NATURAL GAS (5) Conventional gas – unconventional gas
(Total, 2014)
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WHAT IS NATURAL GAS? (6)
Conventional gas: Gas originated somewhere else (the “source” or “mother” rock) and migrated to a porous and permeable formation (the “reservoir rock” or “reservoir”) such as a sandstone or limestone layer sealed on the top by an impermeable cap layer
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WHAT IS NATURAL GAS (7)
Unconventional gas: Coalbed Methane (CBM) gas (gas formed and yet present in low permeable coal layers) Tight gas (gas migrated to a low permeability reservoir rock) Shale gas (gas originates in the shale and is still present in the shale) Gas hydrates (crystalline ice-like molecular complexes formed from mixtures of water and gas molecules) present in the top few hundred meters of sediment beneath continental margins at water depths between a few hundred and a few thousand meter, and in permafrost sediments in Arctic areas. (the terminology may be used differently, for example “shale gas” my be denoted “tight gas”) Shale Gas - Hack
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ECONOMICS OF GAS EXPLOITATION What makes gas production of a field successful economically; i.e. when has a well (borehole) a sufficient flow rate of gas (q); Not a single parameter is important, but many factors play a role:
𝑞=
𝑘 ℎ 𝑝 − 𝑝𝑤𝑓 𝑟 141.2 𝛽 𝜇 ln 𝑟𝑒 − 0.75 + 𝑠 𝑤
𝑞 = 𝑓𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 𝑘 = 𝑝𝑒𝑟𝑚𝑒𝑎𝑏𝑖𝑙𝑖𝑡𝑦 𝑝 = 𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑟𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟 𝑝𝑤𝑓 = 𝑓𝑙𝑜𝑤𝑖𝑛𝑔 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑎𝑡 𝑏𝑜𝑡𝑡𝑜𝑚 ℎ𝑜𝑙𝑒 ℎ = 𝑛𝑒𝑡 𝑝𝑎𝑦 𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 𝑜𝑓 𝑟𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟 𝑖. 𝑒. 𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 𝑜𝑓 𝑝𝑟𝑜𝑑𝑢𝑐𝑖𝑛𝑔 𝑙𝑎𝑦𝑒𝑟 𝛽 = 𝑟𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟 𝑣𝑜𝑙𝑢𝑚𝑒 𝑓𝑎𝑐𝑡𝑜𝑟 (= 𝑔𝑎𝑠 𝑝𝑟𝑜𝑝𝑒𝑟𝑡𝑦) 𝜇 = 𝑔𝑎𝑠 𝑣𝑖𝑠𝑐𝑜𝑠𝑖𝑡𝑦 𝑟𝑒 = 𝑑𝑟𝑎𝑖𝑛𝑎𝑔𝑒 𝑎𝑟𝑒𝑎 (𝑖. 𝑒. 𝑎𝑟𝑒𝑎 𝑑𝑟𝑎𝑖𝑛𝑒𝑑 𝑏𝑦 𝑤𝑒𝑙𝑙 𝑜𝑟 𝑠𝑖𝑧𝑒 𝑜𝑓 𝑟𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟) 𝑟𝑤 = 𝑟𝑎𝑑𝑖𝑢𝑠 𝑏𝑜𝑟𝑒ℎ𝑜𝑙𝑒 𝑠 = 𝑠𝑘𝑖𝑛 𝑓𝑎𝑐𝑡𝑜𝑟 (𝑓𝑎𝑐𝑡𝑜𝑟 𝑓𝑜𝑟 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑑𝑟𝑜𝑝 𝑛𝑒𝑎𝑟 𝑤𝑒𝑙𝑙) (Petrowiki, 2014)
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ECONOMICS OF GAS EXPLOITATION(2) 𝑞=
𝑘 ℎ 𝑝 − 𝑝𝑤𝑓 𝑟 141.2 𝛽 𝜇 ln 𝑒 − 0.75 + 𝑠 𝑟𝑤
𝑞 = 𝑓𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 𝑘 = 𝑝𝑒𝑟𝑚𝑒𝑎𝑏𝑖𝑙𝑖𝑡𝑦 𝑝 = 𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑟𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟 𝑝𝑤𝑓 = 𝑓𝑙𝑜𝑤𝑖𝑛𝑔 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑎𝑡 𝑏𝑜𝑡𝑡𝑜𝑚 ℎ𝑜𝑙𝑒 ℎ = 𝑛𝑒𝑡 𝑝𝑎𝑦 𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 𝑜𝑓 𝑟𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟 𝑖. 𝑒. 𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 𝑜𝑓 𝑝𝑟𝑜𝑑𝑢𝑐𝑖𝑛𝑔 𝑙𝑎𝑦𝑒𝑟 𝛽 = 𝑟𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟 𝑣𝑜𝑙𝑢𝑚𝑒 𝑓𝑎𝑐𝑡𝑜𝑟 (= 𝑔𝑎𝑠 𝑝𝑟𝑜𝑝𝑒𝑟𝑡𝑦) 𝜇 = 𝑔𝑎𝑠 𝑣𝑖𝑠𝑐𝑜𝑠𝑖𝑡𝑦 𝑟𝑒 = 𝑑𝑟𝑎𝑖𝑛𝑎𝑔𝑒 𝑎𝑟𝑒𝑎 (𝑖. 𝑒. 𝑎𝑟𝑒𝑎 𝑑𝑟𝑎𝑖𝑛𝑒𝑑 𝑏𝑦 𝑤𝑒𝑙𝑙 𝑜𝑟 𝑠𝑖𝑧𝑒 𝑜𝑓 𝑟𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟) 𝑟𝑤 = 𝑟𝑎𝑑𝑖𝑢𝑠 𝑏𝑜𝑟𝑒ℎ𝑜𝑙𝑒 𝑠 = 𝑠𝑘𝑖𝑛 𝑓𝑎𝑐𝑡𝑜𝑟 (𝑓𝑎𝑐𝑡𝑜𝑟 𝑓𝑜𝑟 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑑𝑟𝑜𝑝 𝑛𝑒𝑎𝑟 𝑤𝑒𝑙𝑙)
Hence: To increase flow: Increase permeability (fracking) Increase number of wells
(Petrowiki, 2014)
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ECONOMICS OF GAS EXPLOITATION (3) Number versus quantity of resources:
(Masters, 1979)
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ECONOMICS OF GAS EXPLOITATION (3)
Hence: Expected large quantities of difficult to produce gas to be present
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ESTIMATED RESOURCES UNCONVENTIONAL GAS
(PacWest, 2014)
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POTENTIAL GAS PRODUCTION IN USA
(EIA, 2014)
Lower 48 = the contiguous United States (48 states excluding Alaska, Hawaii, and all off-shore U.S. territories and possessions) Shale Gas - Hack
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POTENTIAL IN THE NETHERLANDS Potential shale gas formations
(between 1 and 5 km depth): Lower Jurassic: Posidonia Shale (1750-1850 m depth*)
Aalburg Formation (2075-2250 m*) Carboniferous: Geverik (926-992 m* depth in Limburg) Potential coalbed methane layers: Carboniferous (Namurian) (500-2000 m* depth) *) note depth indications are approximate and vary over The Netherlands
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POTENTIAL IN THE NETHERLANDS(2) Potential shale gas and/or oil formations1: High potential: Posidonia Shale2 (1750-1850 depth5) Pyritic dark-grey to brownish-black, bituminous, fissile3 shale4 Less potential: Aalburg Formation (2075-2250 depth5) Sequence of dark-grey, calcareous, locally silty or sandy, shale4 containing occasional thin limestone beds and containing pyrite Geverik formation (926-992 m5 depth in Limburg)
Dark-grey or black, bituminous, shaly claystones, with abundant intercalated laminae of graded siltstone and very fine-grained sandstone. Notes: 1) Descriptions from DINOloket, 2014; 2) Posidonia Shale may contain large quantities of oil; 3) Fissile means easily split along closely spaced planes; 4) By some denoted claystone (DINOloket-Aalburg, 2014, DINOloket-Posidonia, 2014); 5) depth indications are approximate and vary over The Netherlands
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POTENTIAL IN THE NETHERLANDS (3) Two concessions:
Shale: Cuadrilla (an independent UK company based in Staffordshire, specialized in shale gas exploitation)
(Coalbed methane) (concession returned) (Queensland Gas Company Ltd.(Australian company)
(Hans et al., 2012)
(Halliburton, 2011)
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FRACKING
To obtain gas flow out of shale permeability has to be increased by fracking
(Total E&P, 2014) 13/05/2014 Shale Gas - Hack
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LIFE CYCLE
(Louwen, 2011)
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FRACKS
(Baker Hughes, 2014)
The fracking fluid is pumped with high pressure into holes in the horizontal pipe (downhole fluid pressures 60-70 MPa) The fracking process causes • small fractures in the shale • typical aperture width: about a few sand grains with a maximum of 12 mm (NOGEPA, 2011) • typical length: 100 to 200 meters
The exact fracture propagation is dependent on location specific geological circumstances (i.e. virgin stress field & stiffness and strength of shale) Shale Gas - Hack
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IS FRACKING SPECIAL?
Not really: Fracking has been used for 60 years in exploitation of: conventional oil & gas geo-energy sometimes for water exploitation
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WATER REQUIRED
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WATER REQUIRED(2) Fracking water required 10,000 m3 per well (Hans et al., 2012) Quantity of water returned between 5 and 40 % of fracking fluid injected depending on characteristics shale (Hans et al., 2012) In the US water is disposed as waste water (with probably environmental consequences) Likely in NL water will be treated (cleaned) and re-used
Claims that fracking uses extreme quantities of water are strange: In Pennsylvania, US: 9.5 billion gallons of water used daily of which natural gas development consumes 1.9 million gallons a day (mgd), livestock use 62 mgd, mining, 96 mgd, and industry, 770 mgd.
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WATER REQUIRED(3)
Claims that fracking uses extreme quantities of water are strange; water usage in major shale gas fields (i.e. “plays”) in the US:
(modified after Arthur, 2009)
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ADDITIVES IN FRACKING WATER
Items normally added to the fracking water: • Sand (to keep the fracks open) • Chemicals: Additives to free the gas molecules Additives to allow easy flow of the water and gas
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ADDITIVES IN FRACKING WATER(2) Chemical additives are proprietary and confidential, and thus mostly not disclosed to the public in detail; Generally the additives are described as harmless, and equal or similar to ingredients used in households; a hydraulic fracturing company describes the additives as follows: (quote) “The rest (i.e. the additives) consists of ingredients we use every day at home or at work – things used in foods, food additives and preservatives, cosmetics and other pharmaceuticals, dishwashing liquid, laundry detergents, household cleaners, table salt, antiperspirant, and water purification.” (Baker Hughes, 2014)
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ADDITIVES IN FRACKING WATER(3) In the Netherlands it will be impossible to keep the additives completely confidential;
All details of the chemical additives have to be made available to the Government (“Staatstoezicht op de Mijnen”; SodM) and the Commission for Environmental Impact (“Commission voor de MER”), who will asses the potential risks for environment and public
Generally based on many independent assessments, the additives are not deemed to be an unacceptable risk for environment nor public, when good control and best practices are applied and strictly supervised by the government.
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RETURN FORMATION WATER
When exploiting shale gas part water will be returned that consists of: fracking fluid and formation water (i.e. natural water present in the shale)
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RETURN FORMATION WATER(2) The returned water may contain chemicals naturally present in the shale: • Radioactive material (e.g. radon, uranium, radium, iodine, thorium, and potassium) Will have to be cleaned or returned in formation • Other chemicals are yet largely unknown
In NL: water before final disposal will have to be treaded according standards for waste water
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POLLUTION OF GROUND AND DRINK WATER Possible pollution of drinking water by fracking fluids:
Possible sources: • Fracking fluid entering water reservoir formations via fracks or direct trough permeable layers between shale and drink water reservoir • Leakage along borehole
• Spills on surface
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POLLUTION OF GROUND AND DRINK WATER(2) Fracking fluid entering ground- and drink-water reservoir formations: Very unlikely to happen in NL: • Vertical distance between fracking borehole and drink water reservoir formations more than 1,000 m. • Fracking fluid with additives is too dense to migrate upwards over large distances through narrow cracks • Many near to impermeable layers present in between • Large quantity of fracking fluid is returned with the gas production (although this is not known in detail yet) • If it happens, it is possibly such a small quantity with relatively not very harmful additives that it will not be a serious risk
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POLLUTION OF GROUND AND DRINK WATER(3) An often cited literature reference to illustrate the danger of pollution of groundwater is an article by Tom Myers “Potential Contaminant Pathways from Hydraulically Fractured Shale to Aquifers” (Myers, 2012) However, this article is based on an likely overly simplified model and geology, and is heavily criticized by Saiers and Barth from Yale School of Environmental Studies (Saiers & Barth, 2012): (quote from Saiers & Barth, 2012) “We recognize models represent only approximations of reality, but Myers’ modeling framework neglects critical hydrologic processes, misrepresents physical conditions that drive groundwater flow, and is underpinned by simplifications that are too severe and unnecessary. Owing to these shortcomings, Myers’ findings should not be interpreted as reasonable predictions of the response of groundwater flow and contaminant migration to hydraulic fracturing.”
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POLLUTION OF GROUND AND DRINK WATER(4) Pollution from well; well containment: Proper installed boreholes with proper cement sealing, best practices applied, and proper governmental supervision will likely prevent leakage along boreholes Experience: many existing boreholes for conventional gas and oil production have never leaked (as far as known).
(Halliburton, 2011)
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POLLUTION OF GROUND AND DRINK WATER(4)
Spills on surface Should be under control by best practices and supervision
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GAS IN DRINK WATER “GasLand” movie with burning tap water (“GasLand” 2010): Likely at least some of the portrayed cases in the movie were because the owner had drilled his (domestic - private) water well into a formation that contained pockets with shallow natural gas, which gas had nothing to do with the drilling for and exploitation of deep shale gas nearby (OGCC, 2010)
Is pollution with gas always completely nonsense: No, if borehole is not properly cemented, gas may leak and intrude drink water formations Remedy: should be under control by best practices and supervision
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LEAKAGE AND CONVECTION ALONG BOREHOLE Theoretically possible flow of fracking fluid along borehole by convection mechanisms: Temperature along borehole relatively high (due to the high temperature gas & water in the borehole), could cause water in the formations surrounding the borehole to start moving up due to convection Never happened with existing gas and oil boreholes in NL; hence deemed to be very unlikely for shale gas boreholes
Often referred publications in which is stated that this is a serious risk are probably highly questionable. The publications are often based on an extremely (over-) simplified geology which has nothing to do with reality
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EARTH TREMORS Fracking may cause earth tremors and may trigger earthquakes Tremors due to fracking process: • In the UK < 2.5 magnitude • Unlikely to be more • Only a problem for very (extremely) sensitive installations Triggering Tectonic Earthquakes: • The insertion of fluid under high pressure in an existing (tectonic) fault may release stored deformation energy and hence earthquakes • Magnitude unknown • Remedy: Safe area has to be defined around existing faults (Bremmer et al., 2013) Note that “compaction earthquakes”, i.e. Earthquakes as result of compaction of the shale (Groningen field (The Netherlands) type earthquakes) are highly unlikely because the shale is a very tight structure that will not or only marginally compact when gas is exploited. Shale Gas - Hack
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EARTHQUAKES Natural (tectonic) earthquakes in NL:
(Hans et al., 2012)
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NUISANCE FOR SURROUNDINGS Many more boreholes have to be drilled for shale gas exploitation than for a conventional gas field. Many different locations (distances in the order of 5 to 10 km) and many boreholes per location (up to 14)
Needs relatively large quantities of large equipment to be transported
Noise
May be tremors from fracking
(Halliburton, 2011)
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EXAMPLE FIELD WITH LOCATIONS
(Halliburton, 2011)
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CONCLUSION For one of the other reason unconventional gas exploitation has a bad name, and a massive discussion is the result: In which many bogus arguments are used, but On the other hand some serious concerns are certainly justified too, such as triggering earthquakes, pollution from bad practices, and nuisance for the surroundings. Are the risks controllable:
Yes, seems very well controllable, although yet unknowns have to be filled in by test drilling
(Halliburton, 2011)
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REFERENCES Arthur, J.D., 2009. Prudent and sustainable water management and disposal alternatives applicable to shale gas development. In: The Ground Water Protection Council, San Antonio, Texas, January 2009. ALL Consulting, Tulsa, OK, USA. 20 slides. http://energyindepth.org/docs/pdf/ALL-Shale-Gas-Water.pdf [Accessed: 10 May 2014] Baker Hughes, 2014. View of fractured rock. Baker Hughes Incorporated, Houston, USA. http://public.bakerhughes.com/shalegas/fracturing.html [Accessed: 12 May 2014] Bremmer, J.M., Van de Graaff, W.J.E., Hack, H.R.G.K., Heimovaara, T.J., Huizer, J.A., Soppe, M.A.A., Van der Spek, K.A.A., Verheijen, L.H.J. & Vogel, R.L., 2013. Beoordeling effectstudie schaliegaswinning. 023-114. Commissie voor de milieueffectrapportage (MER), Utrecht, The Netherlands. ISBN: 978-90-421-3853-7. p. 24 (in Dutch) DINOloket, 2014. Geological Survey - TNO, Utrecht, The Netherlands. http://www.dinoloket.nl/ [Accessed: 10 May 2014] DINOloket-Aalburg, 2014. Aalburg Formation ATAL. Geological Survey - TNO, Utrecht, The Netherlands. http://www.dinoloket.nl/aalburg-formation-atal [Accessed: 10 May 2014] DINOloket-Posidonia, 2014. Posidonia Shale Formation ATPO. Geological Survey - TNO, Utrecht, The Netherlands. http://www.dinoloket.nl/posidonia-shale-formation-atpo [Accessed: 10 May 2014] EIA, 2014. Annual Energy Outlook 2014 with projecttions to 2040 DOE/EIA-0383(2014). U.S. Energy Information Administration (EIA); Office of Communications, Washington. p. 269. www.eia.gov/forecasts/aeo [Accessed: 12 May 2014] Halliburton, 2011. EBN; Notional Field Development; Final Report. p. 239 Hans, I., De Vos, S. & IJpelaar, G., 2012. Shale gas production in a Dutch perspective; Final public report. EBN; Royal Haskoning, Nijmegen, The Netherlands. p. 77. http://www.ebn.nl/Actueel/Documents/2012_Shale-gas-production-in-a-Dutch-perspective_Haskoning.pdf [Accessed: 7 May 2014] Louwen, A., 2011. Comparison of Life Cycle Greenhouse Gas Emissions of Shale Gas with Conventional Fuels and Renewable Alternatives.; Comparing a possible new fossil fuel with commonly used energy sources in the Netherlands. Brolsma, M.J., Worrell, E. & Nieuwlaar, E. (Advs). MSc thesis. Department of Science, Technology and Society, Utrecht University, Utrecht Masters, J.A., 1979. Deep Basin gas trap, western Canada. AAPG Bulletin. 63 (2). pp. 152-181. Myers, T., 2012. Potential Contaminant Pathways from Hydraulically Fractured Shale to Aquifers. Groundwater. 50 (6). DOI: 10.1111/j.1745-6584.2012.00933.x. ISSN: 1745-6584. pp. 872-882. NOGEPA, 2011. Fact sheet: Fracking nader toegelicht. Netherlands Oil and Gas Exploration and Production Association (NOGEPA), The Hague, The Netherlands. http://www.groenerekenkamer.nl/download/NOGEPA-Fact-Sheet-Fracking-NL-Rev3-1.pdf [Accessed: 12 May 2014] (in Dutch) OGCC, 2010. Gasland correction document; Statement of the State of Colorado Oil & Gas Conservation Commission (COGCC) regarding Gasland. Department of Natural Resources; State of Colorado; Oil & Gas Conservation Commission, Denver, USA. www.colorado.gov/cogcc [Accessed: 12 May 2014] PacWest, 2014. Shale/Unconventional Resources. PacWest Consulting Partners, Houston, TX, USA. http://pacwestcp.com/education/shaleunconventional-resources/ [Accessed: 10 May 2014] Peters, R., 2012. Unconventional gas field in the Netherlands; Nederland Gasland; Schaliegas nieuw gas voor NL? TNO Energie, Utrecht Saiers, J.E. & Barth, E., 2012. Potential Contaminant Pathways from Hydraulically Fractured Shale Aquifers. Groundwater. 50 (6). DOI: 10.1111/j.1745-6584.2012.00990.x. ISSN: 1745-6584. pp. 826-828. Total, 2014. Three Main Sources of Unconventional Gas. Total S.A., Paris, France. http://total.com/en/energies-expertise/oil-gas/exploration-production/strategicsectors/unconventional-gas/presentation/specific-fields [Accessed: 10 May 2014] Total E&P, 2014. Total E&P Denmark B.V.; Total/Nordsøfonden, København, Denmark. http://en.skifergas.dk/technical-guide/what-is-hydraulic-fracturing.aspx [Accessed: 12 May 2014]
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