from resources and reserves to carbon isotope anomalies · 2015. 12. 16. · traditional coalbed...
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U.S. Shale GasFrom Resources and Reserves to Carbon Isotope Anomalies
John B. CurtisPotential Gas AgencyColorado School of Mines
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Major U.S. Basins and Shale Plays c. 2007(Where are the Haynesville and Marcellus???)
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Shale Gas Annual Production and Energy Information Administration (EIA) Forecast
0
500
1,000
1,500
2,000
2,500
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
2005
2007
2009
2011
2013
2015
2017
2019
2021
2023
2025
2027
2029
Ann
ual P
rodu
ctio
n, B
cf
CUMEIA Projection
EnCana
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U.S. Shale Gas Annual Production from Five Classic Plays to 2007
Modified and updated from Hill and Nelson, 2000
0
200
400
600
800
1,000
1,200
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
2005
Ann
ual P
rodu
ctio
n, B
cf
New AlbanyLewisBarnettAntrimOhio
Expiration ofSection 29 Tax Credit
EnCana
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Targeted Research – $150 Million
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Acquisitions – >$8 Billion
Source: Trollart.com – Ray Troll
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Resource Development – >$15 Billion
Source:devonenergy.com
Source:devonenergy.com
Source:AAPG
Source:AAPG
Source:chiefoiland gas.com
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Hydrocarbons From Shale – Never Say Die
Growth in Barnett Shale - Ft. Worth Basin
0
100
200
300
400
500
600
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
Ann
ual P
rodu
ctio
n, B
cf
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
4,500
5,000
Prod
ucin
g W
ells
Gas Production Well Count
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Exploration Considerations
• Natural fractures - Friend or Foe?• Facies changes - greater permeability• Kerogen type - I,II,IIS,III• Microbial or thermogenic gas?• Thermal maturation history• MWD - especially w/ gas isotopes
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Geochemical Properties of Gas Shales
Modified from Hill and Nelson, 2000
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Modified from original work by Ira Pasternack
Evolution of Antrim Shale Gas
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Some Elements of a Successful Shale Gas Play
Productivity
Gas-In-PlaceThickness
Organic Richness Maturation
Brittleness
Mineralogy Permeability
Pore Pressure
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Potential Supply of Natural Gas in the United States
Report of thePotential Gas Committee(December 31, 2008)
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Proved Reserves vs Resources
• Known gas reservoirs
• Existing economic conditions
• Existing operating conditions
• Discovered
• Undiscovered
• Effects of technology
• Effects of economics
POTENTIAL GAS AGENCY
COLORADO SCHOOL OF MINES
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Regional Resource Assessment
Data source: Potential Gas Committee (2009)
Traditional 1,673.4 TcfCoalbed 163.0 TcfTotal U.S. 1,836.4 Tcf
353.517.3
455.23.4
24.016.6
193.857.0
51.32.6
274.97.5
374.451.9
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PGC Resource Assessments, 1990-2008
Data source: Potential Gas Committee (2009)
Total Potential Gas Resources (mean values)
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Possible Constraints on Future Gas Supply
Sufficient Supply toMeet Demand
TechnologyResourceBase
EnvironmentalConcerns
Skilled Workforce
Regulatory &Land Issues
Gas Price PipelineCapacity
Rig Availability
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Gas Character Anomalies Found in Highly Productive Shale Gas Wells
John E. Zumberge1
Kevin A. Ferworn1
John B. Curtis2
1GeoMark Research Ltd., Houston, Texas USA2Colorado School of Mines, Golden, Colorado USA
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Pres enta tion Outline
• Background: carbon isotope fractionation; gas wetness and wellsite sample collection during drilling;
• I. Ethane isotope “rollover,” suggestive of in situ gas cracking and more productive wells;
• II. Mud gas isotope “reversals,” indicative of overpressured shales;
• III. Permeability markers from differences in methane isotopic composition between mud (free) and cuttings (adsorbed) gases.
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Background
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Dry Gas and Wet Gas Compos itions
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Wells ite Sampling for Gas Is o topes
mud gas sampling manifold
IsoTube for mud gases
IsoJar for cuttings gases
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Mud Gas and Cuttings Sampling
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Changes in Carbon Is o tope Ra tios with Thermal Matura tion (afte r M. Schoell)
After M. Schoell
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I. Barne tt Sha le Ethane Is o tope “Rollover”
C2 isotope “rollover”
Normal increasing maturity trend
Ethane isotope reversals in
mature eastern Barnett gases
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Barne tt Ethane Is o tope “Rollover”
Normal maturity trendEthane isotope reversal
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Stabilized Produc tion vs Wetnes sStabilized Production vs. Gas Wetness
0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
0 5 10 15 20 25
Gas Wetness (C2+)
Stab
ilize
d Pr
oduc
tion
(msc
f/mon
th)
C2 Isotope“Rollover”C2 Isotope“Rollover”
Wells without isotope “rollover”are never the best producers.
Poorly producing “rollover” wells are often earlier completions. Low TOC and rock properties are also important issues.
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Summary - Ethane Is o tope “Rollover”
• Ethane (and propane) isotope “rollover” occurs in increasingly high-maturity shale-gas wells.
• Behavior is also observed in numerous other gas shales in other basins.
• These wells appear to be among the most productive shale-gas wells:• ? In situ cracking increases the number of smaller
molecules, increasing fluid pressure.• ? Organic material becomes more brittle, leading to
increased kerogen porosity and permeability.
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II. Mud Gas Ethane Is o tope “Revers a ls ”
5,000
6,000
7,000
8,000
9,000
10,000
11,000
12,000
13,000
14,000
15,000-40 -35 -30 -25 -20
Ethane Carbon Isotope, δ13C (‰ )
Mea
sure
d D
epth
, MD
(ft)
5,000
6,000
7,000
8,000
9,000
10,000
11,000
12,000
13,000
14,000
15,0000 4 8 12
Wetness, (C2 - nC5) / (C1 - nC5)
Mea
sure
d D
epth
, MD
(ft)
Bossier / Cotton ValleyHaynesville top of overpressure
Haynesville Example
“normal” maturity isotopic trend
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Barne tt Sha le S tra tigraphy
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Haynesville
Eas t Texas /North La . Oil Dis tribu tion
Jurassic Carbonate SourceJurassic/Cretaceous Reservoirs
Cretaceous Shale SourceCretaceous Reservoirs
Tertiary Shale Source & Reservoir
East Texas Field
Haynes ville -Bos s ie r
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III. Sha le Gas Is o topes asPermeability Markers
4,200
4,300
4,400
4,500
4,600
4,700
4,800
4,900-50 -45 -40 -35 -30
Mea
sure
d D
epth
Headspace Gas - IsoJars
Mud Gas - IsoTubes
MoreFreeGas
More AdsorbedGas
Methane Carbon Isotope
A clear isotopic difference existsbetween methane from mud gases(black squares) and methane fromheadspace gases (red squares).
• Mud gas ~ Free / solution / lost gas
• Headspace gas ~ Adsorbed gas
Larger differences between IsoTube And IsoJar isotopes correlate with increased permeability.
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Well Log Evidence for Poros ity/Permeability Detec tion from Sha le Gas Is o topes
1 2 3 4GR
dt
DEPTH(AT10_) ISOJARS
ISOTUBESAT20CHMN -20
-20-50
-50
2000
2000
0.2
0.2
0.45SPMV-500 -300 0.45
-0.15
-0.15
NPOR LM
V/V
V/VDPHI LM
GAP0 150
Zones of maximum porosity /
permeability
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Shale Gas Analys es as Permeability Markers – Poorer Permeability
4,200
4,300
4,400
4,500
4,600
4,700
4,800
4,900-50 -45 -40 -35 -30
Mea
sure
d D
epth
Headspace Gas - IsoJars
Mud Gas - IsoTubes
MoreFreeGas
More AdsorbedGas
Methane Carbon Isotope
Poorer permeability:Gas eventually evolving off cuttings has more free gas, making methane isotopes more negative.
Headspace Gas
Mud Gas
Free Gas (more negative isotopes)
Adsorbed Gas (more positive isotopes)
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Shale Gas Analys es as Permeability Markers – Bette r Permeability
4,200
4,300
4,400
4,500
4,600
4,700
4,800
4,900-50 -45 -40 -35 -30
Mea
sure
d D
epth
Headspace Gas - IsoJars
Mud Gas - IsoTubes
MoreFreeGas
More AdsorbedGas
Methane Carbon Isotope
Free Gas (more negative isotopes)
Adsorbed Gas (more positive isotopes)
Better permeability:Gas eventually evolving off cuttings is mostly adsorbed gas.
Headspace Gas
Mud Gas
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Conclus ions
• Shale-gas well performance can be correlated to gas character anomalies seen in produced, mud and headspace gas isotopic analyses:– Ethane and propane isotope “rollovers”
indicate in situ cracking at high maturities. – Ethane isotope “reversals” within a single well
demonstrate overpressure/effective seals.– Mud (free) and headspace (adsorbed)
methane isotopic signatures can be used as permeability markers.
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Potential Gas Agency
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Traditional Coalbed Gas Total Pot. Region’sResources Resources Resources Proportion
PGC Area (Mean, Tcf) (M.L., Tcf) (Tcf) of Total L48
Regional Resource Assessment Summary
Gulf Coast 455.2 3.4 458.5 28.1%Rocky Mountain 374.4 51.9 426.3 26.1%Atlantic 353.5 17.3 370.8 22.7%Mid-Continent 274.9 7.5 282.4 17.3%Pacific 51.3 2.6 53.8 3.3%North Central 24.0 16.6 40.6 2.5%Total Lower 48* 1,484.9 99.2 1,632.5
Alaska 193.8 57.0 250.8Total U.S. (means)* 1,673.4 163.0 1,836.4
Data source: Potential Gas Committee (2009) * Separately aggregated total, not arithmetically additive.
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Regional Resource Comparison
Data source: Potential Gas Committee (2009)
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PGC Resource Assessment 2008
Data source: Potential Gas Committee (2009)
ProbableResources Possible
Resources
SpeculativeResources
Probable (existing fields) 441.4 TcfPossible (new fields) 736.9 TcfSpeculative (frontier) 500.7 TcfTotal 1,673.4 Tcf
Total Traditional Resources (mean values) by category
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PGC Resource Assessment 2008
Data source: Potential Gas Committee (2009)
ProbableResources
PossibleResources
SpeculativeResources
Probable (existing fields) 14.2 TcfPossible (new fields) 49.8 TcfSpeculative (frontier) 98.9 TcfTotal 163.0 Tcf
Total Coalbed Gas Resources (mean values) by category