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Hydrofracking for shale gas, oil shale, and geothermal energy

Hydrofracking for shale gas, oil shale, and geothermal energy. MINE 292 – Lecture 23 John A. Meech. What is Hydraulic Fracturing?.

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Hydrofracking for shale gas, oil shale, and geothermal energy

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  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 CO2 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 it may exceed 70% of injected fluid • Fracking is often performed in cased wellbores • Zones to be fractured 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 proppantinto 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

  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 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

  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 tiltmeterarrays to monitor strain

  11. Environment • Practices must become transparent (IP issues) • Air • Water • Injected Fluid (chemicals) • Flowback • Seismicity • Health Effects - methane releases - toxic gases - CO2 - Huge volumes - 1.2 to 3.5 M gal/stimulation - Europe is higher due to depth Microseismic events (1.5-3.0) Very few wells have caused earthquakes of concern • 35 out of 1,000,000 wells have caused • contamination of ground water • - Some chemicals are known carcinogens • - Some chemicals are proprietary - Dissolved metals, brine, radioactivity - water treatment required at site 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 Short- and long-term exposure to contaminated air & water and radon

  12. Media Coverage • Gasland - Josh Fox • Truthland - Colorado Oil and Gas Conservation Commission (COGCC) • Promised Land - Matt Damon • Fracknation - PhelimMcaleer

  13. "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"

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

  15. Vertical vs. Horizontal • Alberta • 70% in 2012 • B.C. • 89% in 2012 • Saskatchewan • 60% (2009-12)

  16. Natural Gas Sources

  17. 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

  18. World Shale Gas Reserves

  19. Shale Gas Reserves – top 15 1. China 36 Tm3 2. United States 24 Tm3 3. Argentina 22 Tm3 4. Mexico 19 Tm3 5. Indonesia 18 Tm3 6. South Africa 14 Tm3 7. Australia 11 Tm3 8. Canada 11 Tm3 9. Libya 8 Tm3 10. United Kingdom 7 Tm3 11. Algeria 7 Tm3 12. Brazil 6 Tm3 13. Poland 5 Tm3 14. Pakistan 2 Tm3 15. Ukraine 2 Tm3

  20. 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 under-ground shale deposits of "tight oil" or shale oil

  21. Canadian Shale Gas

  22. Equipment Required During Operation

  23. Equipment Required During Operation

  24. Casing

  25. Hydraulic Fracturing

  26. First Commercial HF – Oklahoma, 1949

  27. Hydraulic Fracturing

  28. Location Relative to Ground Water

  29. Location Relative to Ground Water

  30. Permeability Ranges • mD = milliDarcy (1 Darcy = 10-12 m2)

  31. Permeability and Darcy's Law 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)

  32. 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 proppantin place

  33. Perforating Gun

  34. Frac-pumping Unit

  35. Data Collection Van

  36. Proppant Transfer Truck

  37. Composition of Fracture Fluid

  38. Micro-Seismic Monitoring

  39. Data Collection of Micro-seismics

  40. Location of Major Shale Gas Resources

  41. Shale Gas Resources

  42. U.S. Domestic Energy Consumption

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