hydraulic fracturing considerations for natural gas wells of the marcellus shale
DESCRIPTION
A 2008 presentation on fraturing in the Marcellus.TRANSCRIPT
September 23, 2008 Copyright (c), ALL Consulting, 2008 1
Hydraulic Fracturing Considerations for Hydraulic Fracturing Considerations for Natural Gas Wells of the Marcellus ShaleNatural Gas Wells of the Marcellus Shale
Authors
J. Daniel Arthur, P.E., ALL ConsultingBrian Bohm, P.G., ALL Consulting
Mark Layne, Ph.D., P.E., ALL ConsultingDave Cornue, P.G., ALL Consulting
Presented at
Ground Water Protection Council 2008 Annual ForumCincinnati, Ohio
September 21‐24, 2008
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Unconventional Unconventional Natural GasNatural Gas
Source: John Perez, Copyright ©, 2008
•
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
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Shale Gas HistoryShale 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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Gas Shale Basins of the U.S.Gas Shale Basins of the U.S.Marcellus/Devonian Shale
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Marcellus FactsMarcellus 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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Data Comparison of Shale PlaysData Comparison of Shale PlaysGas Shale Basin Barnett Marcellus Fayetteville Haynesville Woodford
Est. Arial Extent (sq. mi.) 5,000 95,000 9,000 9,000 11,000
Depth (feet) 6500‐9500 4,000‐8,500 1,000‐7,000 10,500‐13,500 6,000‐11,000
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 (mcf/day/well) 338 3,100 530 625‐1800 415
NOTE: See paper for data sources (Arthur, et. al., September 2008)
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Risk of Groundwater ContaminationRisk of Groundwater Contamination•
A 1988 API study rated Appalachian Basin as low risk to corrosion.
•
Per a 1989 API Study for basins with “reasonable”
likelihood of corrosion, risk probability of injectate reaching a USDW ranged from one in 200,000
to one in 200 million
for wells injecting on a continuous basis.
•
Hydraulic fracturing events in the Marcellus occurs through multiple newly installed concentric casings over a short duration with considerable vertical separation (thousands of feet) between USDWs and with overlying formations that are comprised of confining type zones.
ChristmasTree
Pipeline to Flow Process and Storage
Surface Casing
Intermediate Casing
Cement
Cement
WellFluids
Oil or Gas Zone
Perforations
Production Casing
Cement
Tubing
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Fracturing DesignFracturing 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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Fracture ModelingFracture Modeling
Example Output of a Hydraulic Fracture Stimulation Model.Source: Chesapeake Energy Corporation.
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Fracture MonitoringFracture Monitoring
Monitoring is done on a continuous basis during a
fracture treatment
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Microseismic AnalysisMicroseismic Analysis
Mapping of Microseismic EventsSource: Oilfield Service Company
September 23, 2008 Copyright (c), ALL Consulting, 2008 12
Water Management ConsiderationsWater 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 environment.
Fresh Wa
ter Storage TanksSource: ALL Consulting
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Hydraulic Fracturing FluidsHydraulic 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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Fracture Fluid CompositionFracture 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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ExamplesExamples
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Well SitesWell Sites
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Wellhead ConfigurationsWellhead Configurations
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PerforatingPerforating
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Connections/SealsConnections/Seals
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Well Site MonitoringWell Site Monitoring
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ManifoldManifold
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Sand/ProppantSand/Proppant
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FlowFlow‐‐Back WaterBack Water
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Contact InformationContact Information
J. Daniel Arthur, P.E.darthur@all‐llc.comALL Consulting
1718 S. Cheyenne AvenueTulsa, Oklahoma 74119