isotopic forensic techniques for methane source …...• groundwater geochemistry • differentiate...

Imagine the result Imagine the result

Isotopic Forensic Techniques for Methane Source Discrimination

Julie K. Sueker, Ph.D., P.H., P.E., ARCADIS, Lakewood, CO Boyce L. Clark, Ph.D., P.Hg., ARCADIS, Baton Rouge, LA

George H. Cramer, P.G., ARCADIS, Baton Rouge, LA

Stray Gas Incidence and Response Forum Cleveland, Ohio July 23 – 25, 2012

© 2010 ARCADIS 30 July 2012 2

Overview • Why use stable isotope forensics for stray gas

assessments? • Methane generation mechanisms • Stray gas forensic techniques

• Geochemistry • Isotopes • Geophysics • Well integrity

• Case study • Salt dome storage cavern

gas release

Methane bubbles in swamp

Imagine the result 3

Stray Gas Forensics • Methane derived from numerous sources (biogenic,

thermogenic) • Potential methane release site may have multiple

unrelated methane sources including thermogenic sources • Methane forensic techniques used in various settings to

differentiate methane sources

© 2010 ARCADIS 30 July 2012 4

Methane Generation Mechanisms

• Thermogenic • Coal bed and oil & gas formations

• Biogenic • Methanogenesis – “swamp or

landfill gas” and “drift gas” • Acetate fermentation – “landfill gas”

• Abiogenic • Mantel gas

USGS

© 2010 ARCADIS 30 July 2012 5

Geochemical Techniques • Light hydrocarbon gas composition

• Thermogenic versus biogenic

• Composition of other gases (CO2, O2, H2, Ar, He, etc.) • Gas source, migration pathway

• Groundwater geochemistry • Differentiate water “types”

• Trace CH4 generation pathway

• Identify formation/produced water

1

10

100

1000

10000

100000

0.001 0.01 0.1 1 10

Met

hane

/ Et

hane

Carbon Dioxide / Methane

Biogenic Gas Composition

Thermogenic Gas

Composition

Mixing

© 2010 ARCADIS 30 July 2012 6

Geochemical Techniques

0.001

0.01

0.1

1

10

100

1000

10000

Ba Sr Ca Mg Na + K Cl SO4 CO3 Br

Con

cent

ratio

n (m

eq/L

)

Rainwater Limestone Shale and Sandstone

Upper Devonian Shale Lower Devonian Shale Silurian Shale

Cations Anions

© 2010 ARCADIS 30 July 2012 7


0.001

0.01

0.1

1

10

100

1000

10000


Con

cent

ratio

n (m

eq/L

)

Well A Baseline Well A Post Incident Produced Water

Cations Anions

© 2010 ARCADIS 30 July 2012 8


0.001

0.01

0.1

1

10

100

1000

10000


Con

cent

ratio

n (m

eq/L

)

Well A Baseline Well A Post Incident Produced Water Mixed Water

Cations Anions

"Mixed Water" is a hypothetical mixture of 99.7% "Well A Baseline" and 0.3% "Produced Water"

Post Incident Water ≠ Baseline + Produced Water

Imagine the result 9

What are Isotopes? • Atoms of same element with differing masses

• same # of protons, different # of neutrons

p e-

Hydrogen 1H

n p

e-

Deuterium 2H, D

n p n

e-

Tritium 3H, T

Sum of protons and neutrons is the atomic mass Lighter Heavier

© 2010 ARCADIS 30 July 2012 10

Isotope Techniques • Stable carbon and hydrogen isotopes of methane • Carbon-14 (14C) and 3H of methane • Other isotopic tracers, e.g., 87Sr/86Sr, H and O of water

0 20 40 60 80 100 120 140 160

100,000

10,000

1,000

100

10

1

Not Detected

Not Detected

Landfill Gas

Sewer Gas Swamp Gas Glacial

Drift Gas

Thermogenic Gas

Radiocarbon, 14C (pMC)

Triti

um, 3

H (T

U)

Coleman et al., 1993

© 2010 ARCADIS 30 July 2012 11

Stable Isotope Signatures

-350

-300

-250

-200

-150

-100

-100 -80 -60 -40 -20 0

δ2H

CH

4 (‰

)

δ13C CH4 (‰)

Biogenic Gas (CO2 Reduction)

Biogenic Gas (Fermentation)

Thermogenic Gas ("Natural Gas",

Coal Bed Methane)

Schoell et al., 1993

© 2010 ARCADIS 30 July 2012 12

Molecular and Isotopic Data

-60 -55 -50 -45 -40 -35 -30 -25 -20

0.016

0.014

0.012

0.010

0.008

0.006

0.004

0.002

0

δ13C Methane (‰)

1 / [

Met

hane

/ (E

than

e+Pr

opan

e)] Gas Production Wells

Gas Shows

Water Supply Wells - Baseline

Water Supply Wells - Incident

Shallow “Background” Gas

Production Gas

Mixed Gas

13 © 2010 ARCADIS 30 July 2012

Case Study

Storage Cavern C

Storage Caverns A & B

14 © 2010 ARCADIS 30 July 2012

Typical Gulf Coast Salt Dome 0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

Salt

Cap Rock

Salt Mining Wells

Prepared at the request of counsel

Based on illustration from

www solutionmining org

Natural Gas Storage Cavern

15 © 2010 ARCADIS 30 July 2012

1 5 0

4 0 0

2 , 2 0 0

0

7 0 0

2 , 0 0 0

1 , 0 0 0

Casing Breaches

Identified on

Cavern A Well

1973΄

16˝ Casing / 20˝ Borehole

1195΄


495΄


Cavern Top 2,058΄

36˝ Casing

164΄

Release @ 1,575΄ Release @ 1,535΄ Release @ 1,450΄


Hypothetical Representation

Not to scale

16 © 2010 ARCADIS 30 July 2012 16

1 5 0

3 5 0

3 9 5

5 0 0

7 0 0

3 , 3 0 0

0

1 , 0 0 0

2 , 0 0 0

Theoretical Migration Pathways 500 ft

Cavern A Cavern B

Salt Dome

Cap Rock

Over- burden

17 © 2010 ARCADIS 30 July 2012

1 5 0

4 0 0

2 , 2 0 0

0

7 0 0

2 , 0 0 0

1 , 0 0 0

Plug on Cavern A Well

1973΄


1195΄


495΄


Cavern Top 2,058΄

36˝ Casing

164΄

Plug @ 1,716΄

Release @ 1,575΄ Release @ 1,535΄ Release @ 1,450΄



Not to scale

18 © 2010 ARCADIS 30 July 2012

Preparing Cavern A Well for Snubbing Operations


Photo as of 1-2-04

19 © 2010 ARCADIS 30 July 2012

Snubbing Operations on Cavern A Well


Photo as of 1-5-04

20 © 2010 ARCADIS 30 July 2012

1 5 0

3 5 0

3 9 5

5 0 0

7 0 0

0

1 , 0 0 0

1 , 5 0 0

Theoretical Relief Venting



Not to scale

21 © 2010 ARCADIS 30 July 2012

Installation of Vent Wells


Photo as of 1-11-04

22 © 2010 ARCADIS 30 July 2012

Example of a Vent Well


Photo as of 1-18-04

23 © 2010 ARCADIS 30 July 2012 23

Relief Vent

Bubbles

Legend Storage

Caverns A & B

Prepared at the request of counsel As of 1-28-04

Storage Cavern C

Abandoned Gas Wells Southern Vent

© 2010 ARCADIS 30 July 2012 24

Geochemical Data

1

10

100

1000

10000

100000

0.001 0.01 0.1 1 10

Met

hane

/ Et

hane



Thermogenic Gas Composition

Mixing

© 2010 ARCADIS 30 July 2012 25

-215

-200

-185

-170

-155

-140

-70 -65 -60 -55 -50 -45 -40 -35

δ2H

Met

hane

(per

mil)

δ13C Methane (per mil)

All Samples

Southern Vent

Cavern Gas

Biogenic Thermogenic

Cavern C

Caverns A&B

Isotope Data – All Samples (up to one year of sample collection with several repeat locations)

© 2010 ARCADIS 30 July 2012 26

-175

-170

-165

-160

-155

-150

-145

-50.6 -50.4 -50.2 -50 -49.8 -49.6 -49.4 -49.2 -49 -48.8

δ2H

Met

hane

(per

mil)


90

174

98 77

125 114 153 159

Cavern B 132

118 139

145

70

63

47

41

Cavern C

385

202 218

189

84

244

105

Cavern A

Isotope Data – Southern Vent (one location, many samples)

27 © 2010 ARCADIS 30 July 2012 27

Relief Vent Vents -No Gas Bubbles-Match

Legend

Area of Surface Expression

of Gas (Bubbles)

Estimated Extent of Subsurface

Gas

Storage Caverns A & B

Prepared at the request of counsel As of 1-28-04

Storage Cavern C

Abandoned Gas Wells Southern Vent

Bubbles-No Match

Results

© 2010 ARCADIS 30 July 2012 29

Recent Stray Gas Event

Pipelines

Bayou

Bubbles

Tubing through hole in bottom of pool

To hand pump and sample bag

Rope Rope

6’

1’

© 2010 ARCADIS 30 July 2012 30


1

10

100

1000

10000

100000

0.001 0.01 0.1 1 10

Met

hane

/ Et

hane



Thermogenic Gas Composition

Mixing

© 2010 ARCADIS 30 July 2012 31


-215

-200

-185

-170

-155

-140

-70 -65 -60 -55 -50 -45 -40 -35

δ2H

Met

hane

(per

mil)


All Samples

Southern Vent

Cavern Gas

Biogenic Thermogenic

Cavern C

Caverns A&B

© 2010 ARCADIS 30 July 2012 33

Former Bulk Fuel Terminal

SPH Plume

Sanitary Sewer Line

Former marshland, historic landfill

Sample for gas composition, δ13C and δ2H methane, δ13C CO2, 14C methane and CO2

Demonstrate SPH degradation for natural attenuation: Source of methane in soil gas??

200 feet

© 2010 ARCADIS 30 July 2012 34

Methane Forensic Techniques

• Cost effective and definitive investigation tool

• Highest standard of environmental forensics practice

• Establish baseline conditions • Evaluate extent of gas

migration

isotopic forensic techniques for methane source …...• groundwater geochemistry • differentiate...

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