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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

mailto:[email protected]

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))


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)



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



Gas fields are differentiated in:

Conventional gas and Unconventional gas


WHAT IS NATURAL GAS (5)

Conventional gas – unconventional gas


(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


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”)

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:


(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


(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)


(Masters, 1979)

Number versus quantity of resources:

ECONOMICS OF GAS EXPLOITATION (3)

Hence:

Expected large quantities of difficult to produce gas to be present


ESTIMATED RESOURCES UNCONVENTIONAL GAS


(PacWest, 2014)

POTENTIAL GAS PRODUCTION IN USA


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


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)


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)


(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

LIFE CYCLE


(Louwen, 2011)

FRACKS


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


WATER REQUIRED


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.

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)

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

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)

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.

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)

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

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

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



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 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)



Spills on surface

Should be under control by best practices and supervision

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

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

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.

EARTHQUAKES


(Hans et al., 2012)

Natural (tectonic) earthquakes

in NL:

NUISANCE FOR SURROUNDINGS


(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

EXAMPLE FIELD WITH LOCATIONS


(Halliburton, 2011)

CONCLUSION


(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,

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/strategic-

sectors/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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