A 2008 presentation on fraturing in the Marcellus.

1. Hydraulic Fracturing Considerations for
Natural Gas Wells of the Marcellus Shale
Authors
J. Daniel Arthur, P.E., ALL Consulting
Brian Bohm, P.G., ALL Consulting
Mark Layne, Ph.D., P.E., ALL Consulting
Dave Cornue, P.G., ALL Consulting
Presented at
Ground Water Protection Council 2008 Annual Forum
Cincinnati, Ohio
September 21‐24, 2008
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2. Unconventional
Natural Gas
• Unconventional resource plays are
a growing source of natural gas in
the U.S.
– Coal Bed Methane
– Tight Sands
– Gas Shales
• Since 1998, unconventional natural
gas has increased nearly 65%1.
• Through 2007, total gas from
unconventional plays approached
almost 50% of total natural gas
production in the U.S.1
• For Gas shales, key technologies
have included horizontal drilling
and hydraulic fracturing.
1 Source: Navigant, 2008 Source: John Perez, Copyright ©, 2008
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3. Shale Gas History
• First Commercial Gas well – Fredonia, NY (1821)
– New York’s “Dunkirk Shale” at a depth of less than 30 feet
• Ohio Shale – Big Sandy Field (1880)
• Hydraulic Fracturing used in the Oil & Gas Industry (1950‐60s)
• Barnett Shale – Ft. Worth Basin Development (1982)
• Horizontal wells in Ohio Shales (1980s)
• Successful Horizontal Drilling in Barnett Shale (2003)
• Horizontal Drilling Technology Applied in Appalachian Basin, Ohio and
Marcellus Shales (2006)
• Active Companies in the Marcellus Shale Play
– Chesapeake Energy, Fortuna Energy, Range Resources, North Coast
Energy, Chief Oil & Gas, East Resources, Cabot Oil & Gas, Southwestern
Energy Production, Atlas Energy, and others.
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4. Gas Shale Basins of the U.S.
Marcellus/Devonian Shale
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5. Marcellus Facts
• The Marcellus is a Devonian Black Shale that spans a
distance of approximately 600 miles, trending
northeastward from West Virginia all the way into
New York. By comparison, the Barnett Shale has of
linear extent of only about 120 miles.
• America’s current proved natural gas reserves are in
the range of 200 TCF, the Marcellus has the potential
to increase this by 50 TCF or more.
• The Marcellus Shale has a low permeability, thus
releasing gas very slowly. This is why shale is one of
the last major source of undeveloped natural gas.
However, shales can hold an enormous amount of
gas and the formations are so large that their wells
can produce at steady rates for decades.
• Effective and economic horizontal drilling and
hydraulic fracturing are the primary technologies
enabling the recent surge in shale gas production
from the Marcellus and in other regions.
Outcrops of the Marcellus Shale from Leroy, NY (top) and
Lancaster, NY (bottom). Source: Penn State
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6. Data Comparison of Shale Plays
Gas Shale Basin Barnett Marcellus Fayetteville Haynesville Woodford
Est. Arial Extent (sq. mi.) 5,000 95,000 9,000 9,000 11,000
6500‐
Depth (feet) 4,000‐8,500 1,000‐7,000 10,500‐13,500 6,000‐11,000
9500
Net Thickness (feet) 100‐600 50‐200 20‐200 200 120‐220
BTW (feet) ~1200 ~850 ~500 ~400 ~400
TOC, % 4.5 3‐12 4.0‐9.8 1‐14
Total Porosity, % 4‐5 2‐8
Gas Content, scf/ton 300‐350 60‐220
Water Production (BWPD) 0
Well spacing (Acres) 60‐160 40‐160 40‐560 640
Gas‐In‐Place (TCF) 327 1500 52 717 52
Reserves (TCF) 44 262‐500 41.6 251 11.4
Est. Gas Production
338 3,100 530 625‐1800 415
(mcf/day/well)
NOTE: See paper for data sources (Arthur, et. al., September 2008)
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7. Risk of Groundwater Contamination
• A 1988 API study rated
Appalachian Basin as low risk to
Pipeline to
Christmas
Flow Process
corrosion.
Tree
and Storage • Per a 1989 API Study for basins
Surface with “reasonable” likelihood of
Casing corrosion, risk probability of
Cement injectate reaching a USDW
Intermediate
Casing
ranged from one in 200,000 to
one in 200 million for wells
Cement
Production injecting on a continuous basis.
Casing • Hydraulic fracturing events in
Tubing
the Marcellus occurs through
multiple newly installed
Cement concentric casings over a short
duration with considerable
Well Oil or Gas Zone vertical separation (thousands of
Fluids feet) between USDWs and with
Perforations
overlying formations that are
comprised of confining type
zones.
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8. Fracturing Design
• A key to hydraulic fracturing is that the fractures created during the
stimulation remain in the target zone (e.g., the Marcellus Shale).
• Fractures are designed, engineered, and monitored to assure desired
results are achieved.
• Fracture simulation (or modeling) is commonly used for purposes of
designing the fracturing process. This may include developing
specifications on volumes of fluid and proppant to use, pressures to be
applied, make‐up of fracturing fluids and slurries, etc.
• Microseismic monitoring can also be incorporated into a fracturing
event to gain additional knowledge of the fracture process.
• Data collection in advance of fracturing is also common, including
coring and core analysis, geophysical logging, reservoir characteristics
research, correlation to other wells/stimulations, fracture pressure
analysis, among others.
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9. Fracture Modeling
Example Output of a Hydraulic Fracture Stimulation Model.
Source: Chesapeake Energy Corporation.
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10. Fracture Monitoring
Monitoring is done on a
continuous basis during a
fracture treatment
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11. Microseismic Analysis
Mapping of Microseismic Events
Source: Oilfield Service Company
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12. Water Management Considerations
• Water used for fracture stimulation of the Marcellus
has generally been collected primarily from large
streams.
• Volumes ranging from ~500,000 to more than 5
million gallons of water are typically required for a
horizontal Marcellus well and approximately 300,000
to 500,000 gallons for many vertical wells.
• Fluid return water is collected into steel tanks and
hauled off‐site to approved facilities. Disposal methods
generally include injection into a Class II injection wells
and/or commercial/municipal treatment facility
capable of treating flow‐back water.
• Hydraulic fracturing of gas shales has been a routine
stimulation method for many years, with operations
designed to be protective of groundwater and the Fresh Water Storage Tanks
Source: ALL Consulting
environment.
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13. Hydraulic Fracturing Fluids
• Acids are sometimes used to treat near wellbore damage from drilling
and completion operations, open fractures near the wellbore and
dissolve calcite that is naturally occurring in the fracture system.
• Biocides to prevent growth of bacteria in the well.
• Corrosion Inhibitors to prevent degradation of steel well casings.
• Friction Reducers to assist in pumping the fracturing fluid.
• Scale inhibitors to reduce the build‐up of minerals in the well.
• Guar Gel to thicken the water to help carry the proppant (typically
sand) into the formation
• Breaker to cause the guar gel to “break back” into an easier flowing
fluid so the fluids can be pumped back to the surface without carrying
back the sands.
• Iron Stabilizer to prevent precipitation by keeping ions in a soluble
form.
• Oxygen Scavenger to prevent degradation of the well casing.
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14. Fracture Fluid Composition
NOTE: the above graphic is a hypothetical representation of fracture fluid
composition applicable to a Marcellus Shale hydraulic fracturing event. Fluid
composition varies by well and depending on a variety of factors
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15. Examples
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16. Well Sites
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17. Wellhead Configurations
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18. Perforating
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19. Connections/Seals
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20. Well Site Monitoring
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21. Manifold
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22. Sand/Proppant
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23. Flow‐Back Water
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24. Contact Information
J. Daniel Arthur, P.E.
darthur@all‐llc.com
ALL Consulting
1718 S. Cheyenne Avenue
Tulsa, Oklahoma 74119
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