Hydrofracking for shale gas, oil
shale, and geothermal energy
MINE 292 – Lecture 23
John A. Meech
What is Hydraulic Fracturing?
• HF is a method to transmit fluid or gas pressure
to create cracks or open existing cracks in
hydrocarbon-bearing rock to allow gas or oil to
flow more freely from the formation to the
wellbore
• Process is known as Stimulation
What is Hydraulic Fracturing?
• Method of HF depends on:
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Type of well (vertical or horizontal)
Type of well construction (cement/casing)
Type of fracturing fluid
Cost of method
Wells are fractured from 8 to 40 times over their lives
• Methods
– Pulsed Pressured Water (weeks)
– High-pressure liquid propane gel (two days)
– Explosives (not for shale gas)
Major Concerns
• Waste water treatment and disposal
• Safety of chemicals used
• Possibility of aquifer contamination
Fracturing rocks at depth
• Suppressed by confining pressure from overlying rock
• Tensile fractures require crack surfaces to move apart
• Confining pressure prevents movement
• Effective stress is reduced by increasing fluid pressure
within cracks
• Minimum principal stress is in tension and exceeds
tensile strength of the material
• Fractures are oriented perpendicular to minimum
principal stress
• Hydraulic fracturing in wellbores sometimes used to
determine orientation of principle stresses
Fracturing rocks at depth
Hydraulic fracturing is also applied:
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To stimulate groundwater wells
To precondition or induce rock to cave in mining
To enhance waste remediation (hydrocarbon waste or spills)
To dispose of waste by injection into deep rock formations
To measure rock stress
To enhance permeability for enhanced geothermal systems
To increase injection rates for CO2 sequestration
Fracturing rocks at depth
• Fluid pressure exceeds pressure gradient of the rock
• Proppant used to prevent or slow closure of cracks
• silica sand or resin-coated sand
• ceramic beads and other particulates
• Fluid leaking into permeable rock must be controlled
or else it can exceed 70% of injected fluid
• Fracking is often performed in cased wellbores
• Zones to be fractured are accessed by perforating casing
• Pressures can reach as high as 100 Mpa
• Injection rates can reach up to 265 L/s
Fracturing rocks at depth
• High-viscosity fracturing >>> large dominant fractures
• 'Slickwater' (high rate) fracturing >>> small dispersed
micro-fractures
• Fracture fluid contains water-soluble gels (guar gum) to
increase viscosity and deliver proppant into formation
• Fluid injected into the rock is a slurry of water (90%),
proppants (9.5%) and chemical additives (0.5%)
• Foams, and compressed gases (N2, CO2 and air)
sometimes used
Typical Chemical Additives
Acids - HCl (5-28%) or acetic acid for cleaning perforations
Salt - NaCl to delay breakdown of gel polymers
Polyacrylamide - to minimize fluid/pipe friction
Ethylene glycol - to prevent scale formation
Borates - to maintain fluid viscosity as temperature rises
Na2CO3 / K2CO3 - to maintain effectiveness of cross-linkers
Glutaraldehyde - to disinfect the water
Guar gum (water-soluble gels) - to increases viscosity
Citric acid - to prevent corrosion
Monitoring
• Measure pressure and rate of growth of fracture
• Measure properties of fluid and proppant
• Model length, width, & connectivity of propped fracture
• Inject radioactive tracers to determine profile and locate
fractures
• Monitor micro-seismicity using geophones to estimate
size and orientation of fractures
• Install tiltmeter arrays to monitor strain
Environment
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Practices must become transparent (IP issues)
Air
Water
Injected Fluid (chemicals)
Flowback
Seismicity
Health Effects
Environment
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Practices must become transparent (IP issues)
- methane releases
Air
- toxic gases
Water
- CO2
Injected Fluid (chemicals)
Flowback
Seismicity
Health Effects
Environment
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Practices must become transparent (IP issues)
- Huge volumes
Air
- 1.2 to 3.5 M gal/stimulation
Water
- Europe is higher due to depth
Injected Fluid (chemicals)
Flowback
Seismicity
Health Effects
Environment
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Practices must become transparent (IP issues)
Air
Water
Injected Fluid (chemicals)
Flowback - 35 out of 1,000,000 wells have caused
contamination of ground water
Seismicity - Some chemicals are known carcinogens
- Some chemicals are proprietary
Health Effects
Environment
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Practices must become transparent (IP issues)
Air
Water
Injected Fluid (chemicals)
Flowback - Dissolved metals, brine, radioactivity
- water treatment required at site
Seismicity
Health Effects
Environment
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Practices must become transparent (IP issues)
Air
Water
Microseismic events (1.5-3.0)
Injected Fluid (chemicals)
Very few wells have caused
Flowback
earthquakes of concern
Seismicity
BC Oil and Gas Commission
Health Effects concluded 38 earthquakes
from 2.2 to 3.8 occurred in
Horn River Basin from 2009 to
2011 near pre-existing faults
Environment
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Practices must become transparent (IP issues)
Air
Water
Injected Fluid (chemicals)
Flowback
Seismicity
Health Effects Short- and long-term exposure to
contaminated air & water and radon
Media Coverage
• Gasland - Josh Fox
• Truthland - Colorado Oil and Gas Conservation
Commission (COGCC)
• Promised Land - Matt Damon
• Fracknation - Phelim Mcaleer
"New" Technologies
• Hydrofracking has been in use since late 1940s
• Directional-drilling has evolved to an accuracy
previously unattainable
• "Game-Changer" technology with respect to
fossil fuels as an energy source
• These are clean techniques – no question
• Resistance exists due to "hidden-agendas"
Land Disturbance – much reduced
6 wells (8 fracs/well)
48 vertical wells
Vertical vs. Horizontal
• Alberta
– 70% in 2012
• B.C.
– 89% in 2012
• Saskatchewan
– 60% (2009-12)
Natural Gas Sources
Shale Gas
Shale gas has been produced for over 100 years
in the Appalachian and Illinois Basins in the US
Hydraulic Fracturing was first used in late 1940s
New Drilling technologies has accelerated
development and evolution of shale gas
World Shale Gas Reserves
Shale Gas Reserves – top 15
1. China
2. United States
3. Argentina
4. Mexico
5. Indonesia
6. South Africa
7. Australia
8. Canada
9. Libya
10. United Kingdom
11. Algeria
12. Brazil
13. Poland
14. Pakistan
15. Ukraine
36 Tm3
24 Tm3
22 Tm3
19 Tm3
18 Tm3
14 Tm3
11 Tm3
11 Tm3
8 Tm3
7 Tm3
7 Tm3
6 Tm3
5 Tm3
2 Tm3
2 Tm3
PriceWaterhouseCoopers
"By 2035, shale oil production could boost
world economy by up to $2.7 trillion. US
exports could reach 12% of world’s total oil
production — 14M bbl/day revolutionizing
global energy markets for many decades"
Shale gas exploration has revealed deep underground shale deposits of "tight oil" or shale oil
Canadian Shale Gas
Equipment Required During Operation
Equipment Required During Operation
Casing
Hydraulic Fracturing
First Commercial HF – Oklahoma, 1949
Hydraulic Fracturing
Location Relative to Ground Water
Location Relative to Ground Water
Permeability Ranges
• mD = milliDarcy (1 Darcy = 10-12 m2)
Permeability and Darcy's Law
 
 P
 x
where
ν = superficial fluid velocity (m/s)
κ = permeability (m2)
µ = dynamic viscosity (Pa·s)
ΔP = applied pressure (Pa)
Δx = thickness of the bed (m)
Four Step Process
Step 1
• Pressure the reservoir rock using a fluid to create a fracture
Step 2
• Grow the fracture by continuing to pump fluids into the fracture(s)
Step 3
• Pump proppant materials into the fracture (contained in fracture fluid)
Step 4
• Flow-back to the well to recover fracture fluids while keeping proppant
in place
Perforating Gun
Frac-pumping Unit
Data Collection Van
Proppant Transfer Truck
Composition of Fracture Fluid
Micro-Seismic Monitoring
Data Collection of Micro-seismics
Location of Major Shale Gas Resources
Shale Gas Resources
U.S. Domestic Energy Consumption