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Hydrofracking for shale gas, oil shale, and geothermal energy MINE 292 – Lecture 23 John A. Meech.

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Presentation on theme: "Hydrofracking for shale gas, oil shale, and geothermal energy MINE 292 – Lecture 23 John A. Meech."— Presentation transcript:

1 Hydrofracking for shale gas, oil shale, and geothermal energy MINE 292 – Lecture 23 John A. Meech

2 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

3 What is Hydraulic Fracturing? Method of HF depends on: – 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)

4 Major Concerns Waste water treatment and disposal Safety of chemicals used Possibility of aquifer contamination

5 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

6 Fracturing rocks at depth Hydraulic fracturing is also applied: – 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 CO 2 sequestration

7 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

8 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 (N 2, CO 2 and air) sometimes used

9 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 Na 2 CO 3 / K 2 CO 3 - to maintain effectiveness of cross-linkers Glutaraldehyde - to disinfect the water Guar gum (water-soluble gels) - to increases viscosity Citric acid - to prevent corrosion

10 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

11 Environment Practices must become transparent (IP issues) Air Water Injected Fluid (chemicals) Flowback Seismicity Health Effects

12 Environment Practices must become transparent (IP issues) Air Water Injected Fluid (chemicals) Flowback Seismicity Health Effects - methane releases - toxic gases - CO2

13 Environment Practices must become transparent (IP issues) Air Water Injected Fluid (chemicals) Flowback Seismicity Health Effects - Huge volumes to 3.5 M gal/stimulation - Europe is higher due to depth

14 Environment Practices must become transparent (IP issues) Air Water Injected Fluid (chemicals) Flowback Seismicity Health Effects - 35 out of 1,000,000 wells have caused contamination of ground water - Some chemicals are known carcinogens - Some chemicals are proprietary

15 Environment Practices must become transparent (IP issues) Air Water Injected Fluid (chemicals) Flowback Seismicity Health Effects - Dissolved metals, brine, radioactivity - water treatment required at site

16 Environment Practices must become transparent (IP issues) Air Water Injected Fluid (chemicals) Flowback Seismicity Health Effects Microseismic events ( ) Very few wells have caused earthquakes of concern BC Oil and Gas Commission concluded 38 earthquakes from 2.2 to 3.8 occurred in Horn River Basin from 2009 to 2011 near pre-existing faults

17 Environment 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

18 Media Coverage Gasland - Josh Fox Truthland - Colorado Oil and Gas Conservation Commission (COGCC) Promised Land - Matt Damon Fracknation - Phelim Mcaleer

19 "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"

20 Land Disturbance – much reduced 6 wells (8 fracs/well) 48 vertical wells

21 Vertical vs. Horizontal Alberta – 70% in 2012 B.C. – 89% in 2012 Saskatchewan – 60% ( )

22 Natural Gas Sources

23 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

24 World Shale Gas Reserves

25 Shale Gas Reserves – top China36 Tm 3 2. United States24 Tm 3 3. Argentina22 Tm 3 4. Mexico19 Tm 3 5. Indonesia18 Tm 3 6. South Africa14 Tm 3 7. Australia11 Tm 3 8. Canada11 Tm 3 9. Libya 8 Tm United Kingdom 7 Tm Algeria 7 Tm Brazil 6 Tm Poland 5 Tm Pakistan 2 Tm Ukraine 2 Tm 3

26 PriceWaterhouseCoopers "By 2035, shale oil production could boost world economy by up to $2.7 trillion. US exports could reach 12% of worlds total oil production 14M bbl/day revolutionizing global energy markets for many decades" Shale gas exploration has revealed deep under- ground shale deposits of "tight oil" or shale oil

27 Canadian Shale Gas

28 Equipment Required During Operation

29

30 Casing

31 Hydraulic Fracturing

32 First Commercial HF – Oklahoma, 1949

33 Hydraulic Fracturing

34 Location Relative to Ground Water

35

36 Permeability Ranges mD = milliDarcy (1 Darcy = m 2 )

37 Permeability and Darcy's Law where ν = superficial fluid velocity (m/s) κ = permeability (m 2 ) µ= dynamic viscosity (Pa·s) ΔP = applied pressure (Pa) Δx = thickness of the bed (m)

38

39 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

40 Perforating Gun

41

42 Frac-pumping Unit

43 Data Collection Van

44 Proppant Transfer Truck

45 Composition of Fracture Fluid

46 Micro-Seismic Monitoring

47 Data Collection of Micro-seismics

48 Location of Major Shale Gas Resources

49 Shale Gas Resources

50 U.S. Domestic Energy Consumption


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