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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
13/05/2014Shale Gas - Hack 2
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))
13/05/2014Shale Gas - Hack 3
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)
13/05/2014Shale Gas - Hack 4
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
13/05/2014Shale Gas - Hack 5
WHAT IS NATURAL GAS?(4)
Gas fields are differentiated in:
Conventional gas and Unconventional gas
13/05/2014Shale Gas - Hack 6
WHAT IS NATURAL GAS (5)
Conventional gas – unconventional gas
13/05/2014Shale Gas - Hack 7
(Total, 2014)
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
13/05/2014Shale Gas - Hack 8
WHAT IS NATURAL GAS (7)
13/05/2014Shale Gas - Hack 9
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”)
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:
13/05/2014Shale Gas - Hack 10
(Petrowiki, 2014)
𝑞 =𝑘 ℎ 𝑝 − 𝑝𝑤𝑓
141.2 𝛽 𝜇 ln𝑟𝑒𝑟𝑤
− 0.75 + 𝑠
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 𝑙𝑎𝑦𝑒𝑟𝛽 = 𝑟𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟 𝑣𝑜𝑙𝑢𝑚𝑒 𝑓𝑎𝑐𝑡𝑜𝑟 (= 𝑔𝑎𝑠 𝑝𝑟𝑜𝑝𝑒𝑟𝑡𝑦) 𝜇 = 𝑔𝑎𝑠 𝑣𝑖𝑠𝑐𝑜𝑠𝑖𝑡𝑦
𝑟𝑒 = 𝑑𝑟𝑎𝑖𝑛𝑎𝑔𝑒 𝑎𝑟𝑒𝑎 (𝑖. 𝑒. 𝑎𝑟𝑒𝑎 𝑑𝑟𝑎𝑖𝑛𝑒𝑑 𝑏𝑦 𝑤𝑒𝑙𝑙 𝑜𝑟 𝑠𝑖𝑧𝑒 𝑜𝑓 𝑟𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟) 𝑟𝑤 = 𝑟𝑎𝑑𝑖𝑢𝑠 𝑏𝑜𝑟𝑒ℎ𝑜𝑙𝑒𝑠 = 𝑠𝑘𝑖𝑛 𝑓𝑎𝑐𝑡𝑜𝑟 (𝑓𝑎𝑐𝑡𝑜𝑟 𝑓𝑜𝑟 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑑𝑟𝑜𝑝 𝑛𝑒𝑎𝑟 𝑤𝑒𝑙𝑙)
ECONOMICS OF GAS EXPLOITATION(2)
Hence:
To increase flow:
Increase permeability (fracking)
Increase number of wells
13/05/2014Shale Gas - Hack 11
(Petrowiki, 2014)
𝑞 =𝑘 ℎ 𝑝 − 𝑝𝑤𝑓
141.2 𝛽 𝜇 ln𝑟𝑒𝑟𝑤
− 0.75 + 𝑠
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 𝑏𝑜𝑟𝑒ℎ𝑜𝑙𝑒𝑠 = 𝑠𝑘𝑖𝑛 𝑓𝑎𝑐𝑡𝑜𝑟 (𝑓𝑎𝑐𝑡𝑜𝑟 𝑓𝑜𝑟 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑑𝑟𝑜𝑝 𝑛𝑒𝑎𝑟 𝑤𝑒𝑙𝑙)
ECONOMICS OF GAS EXPLOITATION (3)
13/05/2014Shale Gas - Hack 12
(Masters, 1979)
Number versus quantity of resources:
ECONOMICS OF GAS EXPLOITATION (3)
Hence:
Expected large quantities of difficult to produce gas to be present
13/05/2014Shale Gas - Hack 13
POTENTIAL GAS PRODUCTION IN USA
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Lower 48 = the contiguous United States (48 states excluding Alaska, Hawaii, and all
off-shore U.S. territories and possessions)
(EIA, 2014)
POTENTIALIN THE NETHERLANDS
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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
POTENTIAL IN THE NETHERLANDS(2)
13/05/2014Shale Gas - Hack 17
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
POTENTIAL IN THE NETHERLANDS (3)
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(Hans et al., 2012)
Two concessions:
(Halliburton, 2011)
Shale:
Cuadrilla (an independent UK company
based in Staffordshire, specialized in
shale gas exploitation)
(Coalbed methane)
(concession returned) (Queensland Gas
Company Ltd.(Australian company)
FRACKING
13/05/2014Shale Gas - Hack 19(Total E&P, 2014)
To obtain gas flow
out of shale
permeability has to
be increased by
fracking
FRACKS
13/05/2014Shale Gas - Hack 21
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)
(Baker Hughes, 2014)
IS FRACKING SPECIAL?
Not really:
Fracking has been used for 60 years in exploitation of:
conventional oil & gas
geo-energy
sometimes for water exploitation
13/05/2014Shale Gas - Hack 22
WATER REQUIRED(2)
13/05/2014Shale Gas - Hack 24
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.
WATER REQUIRED(3)
13/05/2014Shale Gas - Hack 25
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)
ADDITIVES IN FRACKING WATER
13/05/2014Shale Gas - Hack 26
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
ADDITIVES IN FRACKING WATER(2)
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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)
ADDITIVES IN FRACKING WATER(3)
13/05/2014Shale Gas - Hack 28
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.
RETURN FORMATION WATER
13/05/2014Shale Gas - Hack 29
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)
RETURN FORMATION WATER(2)
13/05/2014Shale Gas - Hack 30
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
POLLUTION OF GROUND AND DRINK WATER
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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
POLLUTION OF GROUND AND DRINK WATER(2)
13/05/2014Shale Gas - Hack 32
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
POLLUTION OF GROUND AND DRINK WATER(3)
13/05/2014Shale Gas - Hack 33
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.”
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).
13/05/2014Shale Gas - Hack 34
(Halliburton, 2011)
POLLUTION OF GROUND AND DRINK WATER(4)
13/05/2014Shale Gas - Hack 35
Spills on surface
Should be under control by best practices and supervision
GAS IN DRINK WATER
13/05/2014Shale Gas - Hack 36
“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
LEAKAGE AND CONVECTION ALONG BOREHOLE
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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
EARTH TREMORS
13/05/2014Shale Gas - Hack 38
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.
NUISANCE FOR SURROUNDINGS
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(Halliburton, 2011)
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
CONCLUSION
13/05/2014Shale Gas - Hack 42
(Halliburton, 2011)
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
REFERENCES
Arthur, J.D., 2009. Prudent and sustainable water management and disposal alternatives applicable to shale gas development. In: The Ground Water Protection Council,
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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.
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2014]
DINOloket-Posidonia, 2014. Posidonia Shale Formation ATPO. Geological Survey - TNO, Utrecht, The Netherlands. http://www.dinoloket.nl/posidonia-shale-formation-atpo
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Washington. p. 269. www.eia.gov/forecasts/aeo [Accessed: 12 May 2014]
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Society, Utrecht University, Utrecht
Masters, J.A., 1979. Deep Basin gas trap, western Canada. AAPG Bulletin. 63 (2). pp. 152-181.
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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.
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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
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