Copyright T. Bechtel Franklin & Marshall College 2014 Copyright T. Bechtel Franklin & Marshall College 2014 What’s Going on Down There ?!? Timothy D. Bechtel,

Copyright T. BechtelFranklin & Marshall College

2014


2014

What’s Going on Down There ?!?

Timothy D. Bechtel, Ph.D., P.G.

Department of Earth & Environment

Franklin & Marshall College

Hydraulic Fracturing


2014

Life Cycle of an Unconventional O&G Well

1. Site Selection2. Pad Construction3. Drilling and Casing4. Stimulation

a. Perforationb. Hydraulic Fracturingc. Fracture Monitoringd. Fracture Controls

5. Flowback6. Production7. Closure

“Fracking”

“Fracing”Frac’ing


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1. Site Selection

C. Scotese; The Paleomap Project


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The Modern “Shale Fairway”

EMR Canada


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The Catskill Basin

L. Fichter; JMU


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The Result of All This…


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Black Shale

• Phytoplankton, algae, pollen, spores• eaten by zooplankton

• eaten by fish and other macro-organisms

0.05mm

• Die and rain down to make a slimy mud• Far enough offshore for fine sediments only• Reducing bottom conditions for

preservation• poor circulation/anoxia/euxinia

• Compressed to make kerogen• Organic matter also collects NORM

USGS

At each trophic level, biomass is reduced by a factor of ten


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Marcellus Ingredients• Illite• Chlorite• Quartz• Kerogen: ~4 to 15%• Feldspar• Micas• Calcite• Pyrite

• Porosity: ~6 to 10%• Permeability: ~0.005 to 2 md

(Soeder, 1988)


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What Does microDarcy mean?

King, 2012

2 md0.005 md


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Biogenic vs. Thermogenic Gas

EMR Canada

• At depth, kerogen is broken down to make hydrocarbons

• Biogenic gas is only methane – produced as microbes decompose kerogen

• Thermogenic gas is produced by cracking and can generate “wet gas” with methane plus easily liquified ethane, propane, and butane

• At the bottom of the gas window, elevated heat generates “dry gas” with methane only

• Hydrogen and Carbon isotope ratios can discriminate between biogenic and thermogenic gas


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Current Hot Spots

Shallow Wet Gas

Deep High PressureDry Gas

3676 Registered Wells(fracfocus.org, 02/17/2014)


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2. Pad Construction• Roads for transport of heavy equipment for earth moving, materials

transport, and the drill rig itself• Site leveling• Erosion and sediment control structures• Pits for drilling fluids, cuttings, and flowback• Racks for drill string and casing sections• Intense activity on the site and local roads for several weeks

Towanda, PAOctober, 2010Steve Hargreaves/CNN

http://www.marcellus-shale.us/Marcellus-Air-8.htm

June, 2012




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3. Drilling and Casing

• Drill rig, drill string, drill bit

Waynesburg, PASteve Hargreaves/CNN

ABC News

Philly.com


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Drilling Mud

Energy Institute

• Water plus bentonite clay and barite (maybe xantham or guar gum)– Lubricates– Cools– Lifts cuttings

• Chips separated on a shale shaker screen– Provides weight to prevent blow-outs– Provides power for mud drive bits– Re-circulated– Recycled– May pick-up NORM

Joshua Doubek


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Casing

• Conductor Casing– Stabilizes unconsolidated surface material– 24” diameter– Extends approximately 50 feet– Cemented from bottom to surface

• Surface Casing– Protects shallow fresh water aquifers– 20” diameter– Extends ~500 feet– Cemented from bottom to surface

• Intermediate Casing– Protects deeper (often brackish) water– 133/8 ”diameter– Extends ~1,000 feet– Cemented bottom to surface

• Production Casing– Conveys fluids to and from the formation– 51/2 ” diameter– Extends to 5,000 to 10,000 feet in depth– Extends 3,000 to 12,000 feet horizontally– Cemented from toe to surface

NYS Water Resources Institute

Springer

Nearly all (?) the horror stories result from human error here


2014


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4. Stimulation

• Perforation– At completion, the production casing is not in communication

with the formation– Explosive charges in a perf gun are used to punch holes through

the casing and cement

Baker Hughes


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4a. Hydraulic Fracturing• Each well is frac’ed in stages

– Perf gun shoots holes through the casing/grout

– Stage is sealed with packer or ball in a seat

– Fluid is pumped in at high flow rate and high pressure

– Existing and incipient fractures are forced open

T. Engelder

Natural Hydraulic Fractures


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History• Directional drilling (not new)

– Patented in 1859 (for brine wells)– Used to relieve blowouts since ~1925

• Hydraulic Fracturing (not new)– First hydrofrac job in the Hugoton Field, Kansas, 1947

• Nitroglycerine frac’ing in 1890s to 1920s (yikes!)• Project Gasbuggy nuclear frac’ing in 1967 (double yikes!!)

– For the last 40+ years, 94% of gas wells have been “stimulated”

• New Combination of these two– US DOE Eastern Shale Gas Project (1972-1980)

• Initiated in response to OPEC hostilities• Deemed feasible, but not economic

• New economics– dwindling (conventional) supply– increasing demand

• Plus high volume, high pressure

1869; AlleganyHistory.org


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Hugoton Field, 1947

Stanolind Oil

This is what the first frac job looked like


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Eagleford Field, 2012

Now it looks like this


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Schematic

Water

Water

Water

Water

Water

Water

Hyd

rato

r

Gel Concentrate

Ble

nder

Chemical 1

Chemical 2

Chemical 3

Chemical n San

d C

an

Pum

p

Pum

p

Pum

pP

ump

Pum

p

Pum

p

Well

Flowback

High VolumeHigh Pressure


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Dusseault & McLennan, 2009

What is Happening Underground?

Remember 2 md ~ concrete


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Fracture Mechanics• In each frac stage;

– Fractures open primarily perpendicular to s3 (horizontal)

– Fractures propagate preferentially upward (towards the free surface)– Typically follow natural pre-existing or incipient hydraulic fractures– Proppants hold them open when the injection pressure is released– The “dilated zone” is much larger than the “sand zone”

• Shearing and self-propping on minutely flexed discontinuities beyond the sand zone and even beyond the dilated zone enhance permeability

Stress Ellipse(at a point)

s3

s1

Crack opening/orientation– Walls push against s3

– Propagates along s1


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The Nature of the Stimulated Zone

Kaiser et al., 2013

• Cracks propagate along s1

or smax

– Makes sense; they open by pushing against s3 or smin

• Proppant does not go far– Stays in “sand zone”– Creates a halo “dilated

zone”

• Cracks in dilated zone and beyond are “self-propping”


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Demo Time• Plates and shims for fracture wedging (Mode I)

• Phone book demo for shearing (Modes II and III) outside the dilated zone (and rough surfaces are self-propping – like wrinkled paper)

• Stack of blocks for widespread wedging and shearing (with self propping) in a naturally fractured rock mass


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How do we know what is going on a mile or more down and several miles away?

• Frac job monitoring (Nolte-Smith Plots)– Injection rate and bottomhole pressure (BHP)

• Tilt Meter monitoring– “dilated” zones

• Mine-Back experiments– Expensive and rare

• Microseismic monitoring– Acoustic emissions

• Events with magnitudes 1000 to 10000 times smaller than any perceptible earthquake

– Drop a jug of milk


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Microseismic Monitoring

EMR CanadaColors show frac stages


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How High Can they Propagate?

1. High strength units form intended frac barriers

o But are there pre-existing tectonic features?


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How High Can they Propagate?2. The state of stress will not allow vertical fractures at shallow depths

o But are there pre-existing tectonic features?

Vertical fractures

Horizontal fractures


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How High Can They Propagate?3. If a fracture does “go rogue”, it will stop the moment it encounters

a permeable layer– Pressure “bleed-off”

• Environmentally undesirable since this could be a migration pathway for fluids

• Economically undesirable since this could lead to loss of product

– BHP is closely monitored to prevent this• Human error ?


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How High Can they Propagate?4. Zones that are frac’ed are typically much deeper than potable wells

o But are there pre-existing tectonic features?o And are there abandoned O&G wells that extend deeper?

Marcellus Shale(Pinnacle, 2010)


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5. Flowback, 6. Production• Flowback

– Gas pressure pushes frac water back out– Flowback can go on from hours to weeks– Later water is chemically connate*

• Not frac fluid• Flaring

– CH4 as GHG is 24x more powerful than C02

• Production– Fluid gradients are towards the well

• By pipeline? Truck?– Connections = fugitive gas– CH4 24x more powerful than C02

* Brine with NORM, bromides, arsenic, lead, hydrocarbons


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7. Closure• Typically requires cement/bentonite plugs, e.g.;

– 200-foot plug straddling the end of the surface casing shoe– Plug across any oil and gas bearing strata that extends 100 feet

above– Plug extending from 50 feet below to 50 feet above any water-

bearing strata– 50-foot plug at the surface of the wellbore

Groundwater Protection Council, 2011


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Common Concerns• Distribution (5 years worth of energy, but UGI says 100 years to build pipelines)• Consumptive use of fresh water (>30% of US frack jobs occur in chronic drought areas)• Waste fluids (cuttings, drilling mud, and flowback)• Pad clearing (~10 acres per pad, but also roads and pipelines – destruction, degradation and fragmentation)• Road building (high volume of heavy trucks on rural roads)• Drinking water CH4 (biogenic? CBM? Natural pre-existing?)

• Rogue fractures (Davies et al., 2012: 1% of fractures extend >500m)• Fault reactivation (detected by microseismic monitoring)• Induced earthquakes (related to deep injection disposal not frac’ing)• Fugitive emissions (Low CO2 from NG vs. GHG power of CH4 -- Cornell vs. NRDC et al.)

• VOC emissions (frac water additives and flowback hydrocarbons)• Radiation (Radium in fluids, in wells, in cuttings, and Radon in the atmosphere and product, etc.)• Migration of lost frac water (this is the one with no evidence; too recent, or prevented by pressure gradient?)• Rise in STD’s documented in drilling areas (relative to…?)• Dust control (mostly in the arid west)• Light pollution and landscape pollution (e.g. State and National Parks and Forests)• Induced landslides• Blooms of golden algae (salinization of surface waters)• Workers’ exposure to chemicals and proppants• Community disruption Thousands of abandoned wells (from previous O&G era – next slide) Is it really an energy resource? (EROI slide also coming up…)

All of these must be addressed if we use “fracking” to mean the entire process


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Preachy Stuff Warning


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The “News” is Often Uninformed or Spun


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I Encourage You to Ponder…• How is it different from conventional oil and gas?• Do we need it ?• Should we do it ?• Should we ban it ?• Should we regulate it ?

– How tightly ?– What level of taxation ?

• Could it be a “bridge” to renewables (replacing coal)?• Will we use it as a bridge ?

– Or as energy-hungry humans burn it PLUS coal ?• Are any of the concerns truly intractable from an engineering

standpoint?– What level of risk do we accept for other energy sources ?– What about human error ?

Useful conversations must avoid conflation of distinct issues


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And, Anecdotes are not Evidence

Osborne et al. (2011 and 2013)


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Any Questions ?


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PA DEP estimates that out of >320,000 wells drilled since 1859, less than 4% have been found and plugged (2871 total since 1989, 23 last year)


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Energy Payback Ratio“cradle to grave”

Bre

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Ev

en

Charles Hall (Energy and the Wealth of Nations):“First World societies require an EROI greater than 15 for all energy production to provide enough net energy to sustain food production, water supply, housing, culture, transport, communications, advance science, health care, defense, etc.”

Shale Gas EstimatesHughes, 2013 Aucott, 2013

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Documents

Copyright T. Bechtel Franklin & Marshall College 2014 Copyright T. Bechtel Franklin & Marshall College 2014 What’s Going on Down There ?!? Timothy D. Bechtel,