from floating golf greens to burning cities - usgs · from floating golf greens to burning cities...
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From Floating Golf GreensFrom Floating Golf Greensto Burning Cities to Burning Cities ––
Some reflections on the past, present, Some reflections on the past, present, and future of stray gas identificationand future of stray gas identification
USGS & Pennsylvania DEP
Stray Gas WorkshopNovember 4-6, 2009
Pittsburgh, Pennsylvania
Presented by
Dennis ColemanIsotech Laboratories, Inc.
www.isotechlabs.com
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DISCLAIMERDISCLAIMER
lAlthough the graphics used in this presentation are based on real observations, to protect the confidentiality of the data, in some case studies only “representative data” is shown.
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Definition of Stray GasDefinition of Stray Gas
A plant that occurs where it is not wanted is considered a weed, even a rose can be a weed.
STRAY GAS is a gaseous weed – it is any gas, whether harmful our not, that occurs where it is not wanted.
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HistoryHistory
Prior to the 1970s, natural gases were only distinguishable by differences in their chemical compositions.
For example, bacterial gases can sometimes be differentiated from thermogenic gases by the relative concentrations of hydrocarbons heavier than methane.
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Bacterial gases do not contain significant concentrations of ethane, propane, butane, etc.
Swamp Gas & Landfill Gas
Nitrogen20% Carbon Dioxide
32%
Methane48% Methane
80%
Nitrogen10%
CO210%
Deeper BacterialGases
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Wet ProductionWet ProductionGasGas
Methane 75%
Ethane 10%Propane 5%
Butanes 2%Pentanes 1%Nitrogen 5%
CO2 2%
DryDryProductionProduction
GasGas
Methane98% Nitrogen 1%
CO2 1%
Methane 93%
Propane 1%Nitrogen 2%Other 1%
Ethane 3%
PipelinePipelineGasGas
Most thermogenic gases contain heavier hydrocarbons, Most thermogenic gases contain heavier hydrocarbons, but some do not.but some do not.
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HistoryHistory
Isotopic fingerprinting of stray storage gas was demonstrated at Manlove Underground Gas Storage Field, Fisher Illinois, in the early 1970s
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CH4
Methane
C H
H
H
H
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THE ISOTOPES OF CARBONTHE ISOTOPES OF CARBON
PP
PPP
PN
N
N
N
NN
PP
PPP
PN
N
N
N
NN
N
6 protons7 neutrons
Carbon-13
1.1%
mass = 13
6 protons6 neutrons
Carbon-12
98.9%
mass = 12
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Vacuum
+2500Volts
Magnet
COInlet
2IonizationChamber
ISOTOPE RATIOMASS SPECTROMETER
CO122
.. . . .. . ..... .... .. ... ... .. .
CO132+
+
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StandardSample
0 1 2 3 4 5 6 7 8 9-1-2-3-4-5-6-7-8-9
R = 0.01124P = 1.1112
R = 0.01115P = 1.1024
= -8.0 = 0.0
R = 13C / 12
C
P = 13C%
DELTA SCALE
=R - R
x 1000s x
R sδ
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Preparation of hydrocarbon gasesPreparation of hydrocarbon gasesfor highfor high--precision isotope analysisprecision isotope analysis
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DualDual--inlet isotope ratio mass inlet isotope ratio mass spectrometryspectrometry
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In the 1960s there were only a few active researchers in the area of the geochemistry of natural gas such as
•Silverman•Zartman•Wasserburg•Hitchon•Colombo•Sacket•Stahl
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These Researchers had demonstrated These Researchers had demonstrated thatthat
lMethane produced by bacteria was depleted in 13C and thus had more negative δ13C values than thermally produced methane.
lThe carbon isotopic composition of thermogenic methane varied depending on the nature of the source material and the thermal maturity of the source rock. That is, what went into the pot and how much it was cooked.
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BACTERIA PREFER
“LITE” ISOTOPES
12C
13C
12C 12C 13C13C
13C13C13C 13C
13C13C
Tastes great!!
Less Filling!!
12C
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Storage Gas IdentificationStorage Gas Identification
lStray gas that had leaked from an underground gas storage field was distinguished from the bacterial methane in the groundwater by carbon isotope analysis when compositional analysis alone proved ineffective.
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Hydrocarbon Concentrations, Manlove AreaHydrocarbon Concentrations, Manlove Area
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Variations in Carbon IsotopesVariations in Carbon Isotopes
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Storage Gas IdentificationStorage Gas Identification
lBecause the natural gas brought into the Midwest by pipeline was formed under much different conditions than the native gases in the area, in most situations native thermogenic gas and pipeline gas can also be differentiated.
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NOTE: Slide intentionally reversed to adopt currently accepted convention with negative values to the left.
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lIn the 1970’s, carbon was our only isotopic indicator for differentiating gases.
lMartin Schoell and his group at the German Geological Survey (BGR) introduced the use of hydrogen isotope analysis as another tool in gas identification.
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CH4
Methane
C H
H
H
H
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The Isotopes of HydrogenThe Isotopes of Hydrogen
PN
Deuterium1 proton1 neutron
P
Protium1 proton
0 neutrons
0.01%99.99%mass = 2mass = 1
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δ13C of CH4 (o/oo)
δD o
f CH
4(o / o
o)Isotopic Composition of Methane
Methane from Deep-Sea Sediments and
Water Wells
Methane from Oil and Gas Wells and
Pipelines
-90
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Gas FingerprintingGas Fingerprinting
lTwo genetic groups of gases were identified, Microbial Methane and Thermogenic Methane.
lThe isotopic fingerprint of thermogenic methane was related to thermal maturity.
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(Carbon Dioxide Reduction)
Thermogenic
Marine
Fresh Water
Microbial Gas
C of Methane ( )o/oo13δ
-300
-360-340-320
-280-260-240-220-200-180-160-140-120-100
D o
f Met
hane
(
)/o o o
δ
Gas
Maturat
ion
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4.2
2.3
0.0
0.0
0.0
0.00.0
Thermogenic gas in fresh-water aquifer
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-43.5
-22.6
-91.2
-78.1
-83.3
-84.8-79.4
? Unusual isotopic data resulted in recognizing the effects of bacterial oxidation.
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Oxidation EffectOxidation Effect
lThe discovery of thermogenic methane with an unusually high 13C concentration in a shallow aquifer led us to investigate the affects of bacterial oxidation on the isotopic composition of methane.
lMethanotrophic bacteria were cultured and the composition of the residual, un-oxidized methane, was monitored.
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Methane Oxidation StoryMethane Oxidation Story
• Culture A, 26°CCulture B, 11.5°CCulture B, 26°C
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lThe systematic variations observed in the bacterial cultures allowed us to predict the affect that oxidation would have on the carbon and hydrogen isotopic composition of partly degraded methane
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(Carbon Dioxide Reduction)
Thermogenic
Marine
Fresh Water
Microbial Gas
C of Methane ( )o/oo13δ
-300
-360-340-320
-280-260-240-220-200-180-160-140-120-100
D o
f Met
hane
(
)/o o o
δ
Gas
Oxid
atio
n Ef
fect
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llOn a project where we were asked to test every On a project where we were asked to test every available source of methane overlying a proposed gas available source of methane overlying a proposed gas storage field we found that:storage field we found that:
– Samples from water wells had δ13C values from -70 to -100
– Near surface samples from lakes and swamps had values in the range of -45 to -65, extending into the thermogenic gas range
– The assumption was that this near surface gas was partially oxidized.
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lBut hydrogen isotope analysis indicated that this near-surface gas was not enriched in deuterium as would be expected for partial oxidation, and was instead highly depleted in deuterium (very negative δD values).
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(Carbon Dioxide Reduction)
Thermogenic
Marine
Fresh Water
Microbial Gas
C of Methane ( )o/oo13δ
-300
-360-340-320
-280-260-240-220-200-180-160-140-120-100
D o
f Met
hane
(
)/o o o
δ
Gas
++
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+
Soil Gas and Landfill Gas
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lFollow up work at the BGR demonstrated that this deuterium-depleted methane was in fact bacterial methane that was formed by a different metabolic pathway than were the microbial gases previously observed.
lThe deuterium-depleted near-surface methane was formed by fermentation whereas more deeply-seated microbial methane was formed by CO2 reduction.
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(Carbon Dioxide Reduction)
Thermogenic
Marine
Fresh Water
Microbial Gas
(Fermentation)
Microbial Gas
C of Methane ( )o/oo13δ
-300
-360-340-320
-280-260-240-220-200-180-160-140-120-100
D o
f Met
hane
(
)/o o o
δ
Gas
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At a golf course overlying a gas storage reservoir, methane was observed as a “bubble” in a golf green and it actually “floated” the saturated sod mat. Walking on the green was like walking on an air mattress.
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When the very tight layer of sod When the very tight layer of sod was punctured, the escaping was punctured, the escaping gas could be ignited.gas could be ignited.
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-300
(Carbon Dioxide Reduction)
Thermogenic Microbial Gas
(Fermentation)
Microbial Gas
C of Methane ( )o/oo13δ
-360-340-320
-280-260-240-220-200-180-160-140-120-100
D o
f Met
hane
(
)/o o o
δ
Gas
Storage Storage GasGas
Seep GasSeep Gas
Isotopic analysis indicated that the Isotopic analysis indicated that the gas was microbial methane and not gas was microbial methane and not leakage gas from the storage leakage gas from the storage reservoir.reservoir.
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Further investigation revealed that the Further investigation revealed that the green had been created over buried brush green had been created over buried brush and other organic material. An unusually and other organic material. An unusually high water table resulted in enhanced high water table resulted in enhanced bacterial activity and the generation of bacterial activity and the generation of fermentation methane.fermentation methane.
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Playa VistaPlaya Vista(old Howard Hughes (old Howard Hughes
property)property)
Marina del Rey
LAXLAX
Playa del Playa del ReyRey
UndergroundUnderground
Gas StorageGas Storage
FieldField
Gas seeps in the Playa Vista area of Los Angeles delayed construction until the source of the gas could be identified.
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Oxid
atio
n Ef
fect
GasThermogenic
(Carbon Dioxide Reduction)Microbial Gas
Microbial Gas
C of Methane ( )o/ooδ 13-90 -80 -70 -60 -50 -40 -30
-300
-360-340-320
-280-260-240-220-200-180-160-140-120-100
D o
f Met
hane
(
)/o o o
δ
(Fermentation)
Seep GasesSeep Gases
Monitoring Monitoring ProbesProbes
Storage GasStorage Gas
The gas seeps were found to be natural seeps, and not related toThe gas seeps were found to be natural seeps, and not related tothe gas storage field.the gas storage field.
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Hutchinson Kansas ExplosionHutchinson Kansas ExplosionIn January of 2001 water and then gas suddenly erupted from several abandoned brine wells throughout the city
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(Carbon Dioxide Reduction)
Thermogenic Microbial Gas
(Fermentation)
Microbial Gas
C of Methane ( )o/oo13δ
-300
-360-340-320
-280-260-240-220-200-180-160-140-120-100
D o
f Met
hane
(
)/o o o
δ
Gas
Seeps and vents Seeps and vents within Hutchinsonwithin Hutchinson
Yaggy Storage GasYaggy Storage GasSE Kansas Native GasesSE Kansas Native Gases
Oxid
atio
n Ef
fect
Isotopic analysis was used to compare the seep gases to potential sources in the area
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-180
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-140
-120
-50 -45 -40 -35
δ13C of Methane
δD
of M
etha
neYaggy Storage GasHutchinson SamplesNative Gases
Isotopic analysis showed that the seep gases were very similar to the Yaggy Storage gas, but some native gases also had similar values.
Oxidation Effect
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0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10
Ethane/Methane
Prop
ane/
Met
hane
Yaggy Storage GasHutchinson SamplesNative Gases
Compositional data allowed more completely eliminating native gas as a likely source of the seep gases that had caused the fires
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The gas storage field was nearly 7 miles from downtown Hutchinson
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Gas migration along gravel zone
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(Carbon Dioxide Reduction)
Marine
Fresh Water
Microbial Gas
(Fermentation)
Microbial Gas
C of Methane ( )o/oo13δ
-300
-360-340-320
-280-260-240-220-200-180-160-140-120-100
D o
f Met
hane
(
)/o o o
δ
Thermogenic Gas
Maturat
ion
Early Thermogenic
(Diagenetic?)
The standard genetic classification scheme was based on commercially viable gas deposits. When we consider also trace levels of gas, at the very early stages of thermogenic gas generation, the compositional range must be expanded.
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Diffusion Effect
-500
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0
-110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20
(Carbon Dioxide Reduction)
Marine
Fresh Water
Microbial Gas
(Fermentation)
Microbial Gas
GasThermogenic
D o
f Met
hane
(
)/o o o
δ
C of Methane ( )o/oo13δ
Data from leaking gas bags
Methane samples in gas bags that appeared questionable were re-analyzed several days later. In all cases, the data points were strongly shifted to the right on this figure. This is diffusion fractionation.
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(Carbon Dioxide Reduction)
Thermogenic Microbial Gas
(Fermentation)
Microbial Gas
C of Methane ( )o/oo13δ
-300
-360-340-320
-280-260-240-220-200-180-160-140-120-100
D o
f Met
hane
(
)/o o o
δ
Gas
Migrated Gas
Residual Gas
Diffusion Fractionation
Migrated Gas
Residual GasOriginal Gas
The migrated gas is The migrated gas is depleted in the heavier depleted in the heavier isotopes and the isotopes and the residual gas becomes residual gas becomes enriched in the heavier enriched in the heavier isotopesisotopes
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RULES OF THUMBRULES OF THUMB
lDiffusion fractionation of methane causes a change in δ13C of about 1.4 times the change in δD
lBecause of the scale of our drawings, it appears to affect carbon much more than hydrogen.
lBoth migrating methane and the residual methane may show the effect.
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lAn unaltered migration front is less frequently observed than is an unaltered residual gas– The migrated gas is more likely to occur in an aerobic
environment where it can be consumed by bacteria– The migrated gas is always at lower concentration and is
thus more impacted by oxidation changeslDiffusion fractionation is normally only significant
with small quantities of gas at low concentrations migrating strictly under a concentration gradient.
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-500
-400
-300
-200
-100
0
-110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20
(Carbon Dioxide Reduction)
Marine
Fresh Water
Microbial Gas
(Fermentation)
Microbial Gas
GasThermogenic
D o
f Met
hane
(
)/o o o
δ
C of Methane ( )o/oo13δ
Gas in a well that has not been adequately purged (stagnant gas) can be highly altered.
Gas from storage reservoir
Stagnant gas in unpurged monitoring wells
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Proposed Reaction Pathway for Generation Proposed Reaction Pathway for Generation of Fermentation Methane in a Stagnant Wellof Fermentation Methane in a Stagnant Well
H2O + CO2 H2CO3
lH2CO3 + Fe FeCO3 + H2
l4H2 + CO2 CH4 + 2H2O
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(Carbon Dioxide Reduction)
Thermogenic
Marine
Fresh Water
Microbial Gas
(Fermentation)
Microbial Gas
C of Methane ( )o/oo13δ
-300
-360-340-320
-280-260-240-220-200-180-160-140-120-100
D o
f Met
hane
(
)/o o o
δ
Gas Oxid
atio
n Ef
fect
Diffusion Effect
Stagnant Water Effect
Secondary Effects
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Stable isotope analysis tells us about the formation mechanism of methane but is only slightly impacted by what the source material was.
Naturally occurring radioactive isotopes provide information on the source material from which the methane was formed but are insensitive to the formation mechanism
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Use of “natural” radioactive tracersUse of “natural” radioactive tracers
Radiocarbon and tritium both exist naturally in the atmosphere where they are produced by cosmic raysBoth currently have elevated concentrations in the atmosphere due to the testing of thermo-nuclear bombs in the 1950s and 1960s
Radiocarbon and tritium can be used as tracers of recently formed bacterial methane
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PN
3H (tritium)1 proton, 2 neutrons
~10-15 %
T1/2 = 12.33 yrs
NP
P
PPP
P
N
N
NN
N
6 protons, 8 neutrons
14C (radiocarbon)
~10-10 %
N
T1/2 = 5730 yrs
NN
Natural Radioactive IsotopesNatural Radioactive Isotopes
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6 protons, 8 neutrons
14C
Radioactive Decay of Radioactive Decay of 1414CC
PP
PPP
P
N
N
NN
NN
T1/2 = 5730 yrs
NN
PP
PPP
P
N
N
NN
P
7protons, 7 neutrons
14N
NN
N
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PN N
Tritium1 proton2 neutrons
PN P
Helium-32 protons1 neutron
Half-Life
12.3 Years
DECAY OF TRITIUM
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Year
Triti
um in
Pre
cipi
tatio
n (T
U)
14C
in A
tmos
pher
ic C
O2
(pM
C)
10,000
1,000
100
10
200
180
160
140
120
100
14CTritium
Tritium Decay Curve
Ottawa
St. Louis
Bomb Affect – From atmospheric testing of nuclear devices
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101 samples from 73 landfills
Tritium concentration (TU)0 50 100 500 1,000 5,000 10,000 50,000
Num
ber o
f Sam
ples
0
5
10
15
20
25
30
35Tritium in Landfill Leachates
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0.1 1.0 10 100 1,000 10,000 100,000
Tritium Concentration (T.U.)
LandfillLeachate
GroundWater
SurfaceWater
Freq
uenc
y
Tritium in landfills is mostly from the disposal of luminous paints
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1
10
100
1000
10000
100000
0 20 40 60 80 100 120 140 160
Radiocarbon (pMC)
Triti
um (T
U)
Swamp Gasand
Marsh Gas
LandfillGas
notdetected
SewerGas
Glacial Drift Gas
ThermogenicGas
notdetected
Source Source IdentificationIdentificationof Methaneof Methane
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CONCLUSIONCONCLUSIONIsotopic analysis is a very powerful tool for
identifying the source of stray gas
BUT
It is NOT A SILVER BULLET
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As is always the case for good scienceAs is always the case for good science
It is necessary to consider all available data and lines of evidence
You must be aware of the limitations of your data
And you should choose the solution that best fits the preponderance of the reliable evidence.
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REFERENCESREFERENCESl Coleman, D.D., 1979, The origin of drift-gas deposits as determined by radiocarbon dating of methane, in R. Berger and H.E. Suess,
eds., Radiocarbon Dating: Univ. of Calif. Press, p. 365-387.l Coleman, D.D., 1999. Carbon and hydrogen isotopic composition of early thermogenic gas. AAPG Hedberg Conference, “Natural
Gas Formation & Occurrence,” Durango, CO, June 6-10, 1999.l Coleman, D.D., 2004. Source identification of stray gases by geochemical fingerprinting. Proceedings of the Solution Mining
Research Institute Spring 2004 Technical Meeting, Wichita, Kansas, April 18-20, 2004l Coleman, D. D., C.-L. Liu, K. C. Hackley, and S. R. Pelphrey (1995). Isotopic identification of landfill methane. Environmental
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