FACTORS AFFECTING FORENSIC ANALYSIS AND · PDF file · 2010-10-25factors affecting...

FACTORS AFFECTING FORENSIC ANALYSIS AND FACTORS AFFECTING FORENSIC ANALYSIS AND INTERPRETATION OF IMPACTS FROM STRAY GAS INTERPRETATION OF IMPACTS FROM STRAY GAS

HYDROCARBONS HYDROCARBONS --PRESSURE, MIXING, OXIDATION, DILUTION PRESSURE, MIXING, OXIDATION, DILUTION

Anthony W. Gorody, Ph.D., C.P.G., P.G.Anthony W. Gorody, Ph.D., C.P.G., P.G.

PresidentPresidentPresidentPresident

Universal Geoscience Consulting, Inc.Universal Geoscience Consulting, Inc.

FORENSIC ANALYSISFORENSIC ANALYSIS

�� Provide defensible dataProvide defensible data

•• What and where is the gas well point source?What and where is the gas well point source?

•• When is impact attenuating?When is impact attenuating?

�� Characterize potential point sources and dischargeCharacterize potential point sources and discharge

•• Sample casing head gas and production gasSample casing head gas and production gas

•• Sample free and dissolved gas in groundwaterSample free and dissolved gas in groundwater

Compare source to dischargeCompare source to discharge�� Compare source to dischargeCompare source to discharge

•• Gas ratiosGas ratios

•• Stable isotopesStable isotopes

�� Address factors affecting composition and concentrationAddress factors affecting composition and concentration

�� Fractionation Fractionation –– migration/solubilitymigration/solubility

�� Mixing (stripping biogenic methane)Mixing (stripping biogenic methane)

�� OxidationOxidation

�� DilutionDilution22

PRESSUREPRESSURE

�� Upper 1000Upper 1000--1500 feet of crust highly permeable1500 feet of crust highly permeable

•• Vertical stress < horizontal stressVertical stress < horizontal stress

�� Well bore annulus integrity is key to stray gas Well bore annulus integrity is key to stray gas

sourcessourcessourcessources

•• Accidental blow outsAccidental blow outs

•• Improperly abandoned wells (historic practices)Improperly abandoned wells (historic practices)

•• Failed cement jobsFailed cement jobs

�� Buoyant gas finds shortest path to the surfaceBuoyant gas finds shortest path to the surface

•• Stream valleysStream valleys

•• Water wellsWater wells

•• Breakthrough limits further migration Breakthrough limits further migration 33

�� E.G. RATON E.G. RATON

BASINBASIN

•• Aquifer fluids Aquifer fluids mobilized 1/3 mobilized 1/3

EXTREME PRESSURE NOT REQUIRED TO EXTREME PRESSURE NOT REQUIRED TO MOBILIZE FLUIDS AT SHALLOW DEPTHSMOBILIZE FLUIDS AT SHALLOW DEPTHS

BaselineBaseline

4 month4 monthexcursionexcursion

Return toReturn to mobilized 1/3 mobilized 1/3 mile away while mile away while pressuring bit pressuring bit with air at 800’with air at 800’

Return toReturn tonormalnormal

44

LOW PRESSURE CBG INVADING SHALLOW LOW PRESSURE CBG INVADING SHALLOW AQUIFERS THROUGH OPEN ANNULUSAQUIFERS THROUGH OPEN ANNULUS

TERTIARYTERTIARY

QUARTERNARYQUARTERNARY

�� SAN JUAN SAN JUAN

BASINBASIN

•• Open annulus: Open annulus: historic historic

PICTURED CLIFFSPICTURED CLIFFS

MESAVERDEMESAVERDE

LEWISLEWIS

FRUITLANDFRUITLAND

production production practicespractices

55

BOUYANCYBOUYANCYPRESSURE PRESSURE

ALLOWS GAS ALLOWS GAS MIGRATIONMIGRATION

FROM FROM

OPENOPENANNULUSANNULUS SHALLOWSHALLOW

GAS GAS SOURCESSOURCES

PICEANCE BASIN

FROM FROM ANNULUSANNULUS

CEMENTEDCEMENTEDANNULUSANNULUS

66

CONTAINED GAS CONTAINED GAS RELEASE RELEASE

INTO PRODUCTION INTO PRODUCTION ANNULUSANNULUS

SURFACESURFACE

CASINGCASING

CEMENTCEMENT

FLUIDFLUID

FILLEDFILLED

ANNULUSANNULUS

PRESSUREPRESSURE

(BRADENHEAD)(BRADENHEAD)

Example: 425 psi on Casing headExample: 425 psi on Casing head

Aquifer Fluid Gradient = .438 psi/ftAquifer Fluid Gradient = .438 psi/ft

Equivalent Gas Column = 970’ Equivalent Gas Column = 970’ ORORGradient at base of casing: 0.69 psi/ftGradient at base of casing: 0.69 psi/ft

DEPTHDEPTH

PRODUCTIONPRODUCTION

CASINGCASING

FILLEDFILLED

OPENOPEN

ANNULUSANNULUS

Gradient at base of casing: 0.69 psi/ftGradient at base of casing: 0.69 psi/ft

1. GAS RELEASED1. GAS RELEASEDINTO OPENINTO OPENANNULUSANNULUS

2. GAS RELEASED2. GAS RELEASED

INTO SHALLOWINTO SHALLOW

AQUIFERSAQUIFERS

SHALLOWSHALLOWFRACTURES & FRACTURES & SAND MATRIXSAND MATRIX

GAS INVASIONGAS INVASIONINTO SANDSINTO SANDS

77

GAS FLOWGAS FLOWDEPENDENTDEPENDENT

ON DRAINAGEON DRAINAGEPROPERTIESPROPERTIES

MERCURY INJECTION

1000

10000

100000

Inje

ction P

ressure

, psi

CONVERSION TO GAS/WATER SYSTEM

0

200

400

600

800

1000

1200

0.00 0.20 0.40 0.60 0.80 1.00

Pseudo-Wetting Phase Sat'n, fraction

Ga

s/W

ate

r P

ressu

re,

psia

POROSITY: 15%POROSITY: 15%

PERMEABILITY: 5.38 PERMEABILITY: 5.38 mdmd

MAXIMUMMAXIMUM

BRADENHEAD BRADENHEAD

PRESSUREPRESSURE

1

10

100

0.000.100.200.300.400.500.600.700.800.901.00

Mercury Saturation, fraction of intruded pore space

Inje

ction P

ressure

, psi

LOWEST CAPILLARY LOWEST CAPILLARY

ENTRY PRESSURES ENTRY PRESSURES

THROUGH SHALLOW THROUGH SHALLOW

BEDDING PLANE AND BEDDING PLANE AND

HORIZONTAL FRACTURESHORIZONTAL FRACTURES90 PSI (175’ water column)90 PSI (175’ water column)

WATER WELL WATER WELL

HYDROSTATIC PRESSUREHYDROSTATIC PRESSURE

CAPILLARYCAPILLARY

ENTRY PRESSUREENTRY PRESSURE

CRITICALCRITICAL

GAS SATURATIONGAS SATURATION

88

FREE GAS MOVEMENT IN GROUNDWATER FREE GAS MOVEMENT IN GROUNDWATER UPUP--GRADIENT BOUYANT GAS MIGRATIONGRADIENT BOUYANT GAS MIGRATION

INTERSECTING WATER WELLINTERSECTING WATER WELL

NN SS

WATER WELLWATER WELL

MIGRATION THROUGHMIGRATION THROUGH

PRESSURIZEDPRESSURIZEDGAS SOURCEGAS SOURCE

FRACTURESFRACTURESMIGRATION THROUGHMIGRATION THROUGH

FRACTURES, BEDDING PLANESFRACTURES, BEDDING PLANESAND MATRIXAND MATRIX

99

�� DISCHARGEDISCHARGE

•• Topographic lows (valleys)Topographic lows (valleys)

•• Shallow lineament trends (valleys)Shallow lineament trends (valleys)

•• Water wells (alluvial valleys)Water wells (alluvial valleys)

PRESSURE IS PRESSURE IS REQUIRED TO REQUIRED TO

DISPLACE DISPLACE WATERWATER

IN A WELLIN A WELL

0’0’

50’50’

100’100’

WATER PRESSURE WATER PRESSURE

AT BASE OFAT BASE OF

175’ WATER COLUMN175’ WATER COLUMN

GAS PRESSUREGAS PRESSURE

BELOWBELOW

SEALSEAL

INCREASESINCREASES

CAPCAP

RELEASEDRELEASED

FOLLOWED BYFOLLOWED BY

FIZZINGFIZZING

150’150’

200’200’

75.15 psi75.15 psi

++

11.9 psi ATMOSPHERIC @ 5800’ 11.9 psi ATMOSPHERIC @ 5800’

= 87 PSI minimum pressure= 87 PSI minimum pressure

FIZZINGFIZZING

MINIMUMMINIMUMGAS ENTRYGAS ENTRYPRESSUREPRESSURE

INTO WELL BOREINTO WELL BORE>87 psi>87 psi

1010

DISSOLVED GAS MOVEMENT IN GROUNDWATER DISSOLVED GAS MOVEMENT IN GROUNDWATER DOWNGRADIENT DISSOLVED GAS MIGRATIONDOWNGRADIENT DISSOLVED GAS MIGRATION

NN S

WATER WELLWATER WELL

BOUYANT BOUYANT THERMOGENICTHERMOGENICGAS SOURCEGAS SOURCE1111

�� REMEDIATIONREMEDIATION

•• IImbibitionmbibition from depth to surfacefrom depth to surface

WHEN ARE GAS SOURCE SIGNATURES WHEN ARE GAS SOURCE SIGNATURES UNIQUE?UNIQUE?

�� Production gases always vary from well to wellProduction gases always vary from well to well

•• Source rock typeSource rock type

•• Source rock maturitySource rock maturity

•• Migration and migration fractionationMigration and migration fractionation

•• Reservoir Reservoir compartmentationcompartmentation (mixed @ 100,000 yrs)(mixed @ 100,000 yrs)•• Reservoir Reservoir compartmentationcompartmentation (mixed @ 100,000 yrs)(mixed @ 100,000 yrs)

�� Source to discharge composition constant when:Source to discharge composition constant when:

•• No migration fractionationNo migration fractionation

•• No mixing with other sourcesNo mixing with other sources

�� BiogenicBiogenic

�� Thermogenic (historic releases)Thermogenic (historic releases)

1212

INCREASINGINCREASING

VARYINGVARYING

SOURCE SOURCE

ROCKROCK

GAS RATIOS ARE UNIQUEGAS RATIOS ARE UNIQUE

PRODUCED GAS PRODUCED GAS DENVER BASINDENVER BASIN

THERMOGENIC BIOGENIC GAS MIXTURE


THERMALTHERMAL

MATURITYMATURITY

1313

GAS RATIOS ARE UNIQUEGAS RATIOS ARE UNIQUE


THERMALTHERMAL

MATURITYMATURITYVARYINGVARYING

SOURCE SOURCE

ROCKROCK

PRODUCED GAS PRODUCED GAS DENVER BASINDENVER BASIN

1414

SOMETIMES PRESENCE OR ABSENCE SUFFICIENTSOMETIMES PRESENCE OR ABSENCE SUFFICIENTTO ELIMINATE POTENTIAL SOURCESTO ELIMINATE POTENTIAL SOURCES

20 mg/L26 mg/L

DE

LTA

D M

ET

HA

NE

pe

r m

ilD

ELTA

D M

ET

HA

NE

pe

r m

il

23 mg/L

Fruitland Well #1

Fruitland Well #2

Fruitland Well # 3

FRUITLAND GAS NOT SOURCEFRUITLAND GAS NOT SOURCE

OF GAS IN THIS WATER WELLOF GAS IN THIS WATER WELL

DELTA DELTA 1313C METHANE per milC METHANE per mil

DE

LTA

D M

ET

HA

NE

pe

r m

ilD

ELTA

D M

ET

HA

NE

pe

r m

il

WATER WELL SITE 595

WATER WELL SITE 595

WATER WELL SITE 595

CASING HEAD CASING HEAD AND AND

PRODUCTION PRODUCTION GAS GAS

COMPOSITIONCOMPOSITIONNOT NOT

PICEANCE BASINPICEANCE BASIN

NOT NOT NECESSARILY NECESSARILY

THE SAMETHE SAME

1616

SHALLOW COMMERCIAL GAS SANDS IN RULISON FIELD SHALLOW COMMERCIAL GAS SANDS IN RULISON FIELD DIFFER FROM UNDERLYING WILLIAMS FORKDIFFER FROM UNDERLYING WILLIAMS FORK

3.4

3.6

3.8

4

4.2

4.4

4.6

C2/C

3

10 15 20 25 30 35 40

W 27-3

W 46-11

W 86-29

W 13-3

W 14-24W 14-34W 15-5

W 18-27

W 19-28

PA 21-34PA 24-21

PA 32-29PA 312-21

RMV 37-33

RMV 43-28A

GV 21-35

GV 25-27

GV 75-3

LANGSTAFF 109+ BacterialMethane Trend

Maturity Trend

Source Rock Trend

2

2.5

3

3.5

Sum

C4/S

um

C5

3.4 3.6 3.8 4 4.2 4.4 4.6

W 27-3

W 46-11

W 86-29

W 13-3 W 14-24W 14-34

W 15-5

W 18-27W 19-28

PA 21-34

PA 24-21

PA 32-29

PA 312-21

RMV 37-33

RMV 43-28A

GV 21-35

GV 25-27

GV 75-3

LANGSTAFF 109

10 15 20 25 30 35 40 C1/C2

Wasatch Williams Fork

3.4 3.6 3.8 4 4.2 4.4 4.6 C2/C3


1.1

1.2

1.3

1.4

1.5

1.6

1.7

iC5/n

C5

0.9 1 1.1 1.2 1.3 1.4 iC4/nC4

W 27-3W 46-11

W 86-29

W 13-3

W 14-24W 14-34W 15-5

W 18-27

W 19-28

PA 21-34

PA 24-21

PA 32-29PA 312-21

RMV 37-33

RMV 43-28AGV 21-35

GV 25-27

GV 75-3

LANGSTAFF 109


0.89

0.9

0.91

0.92

0.93

0.94

0.95

0.96

0.97

Dry

ness (

C1/C

1+

)

0 1 2 3 4 % Non Hydrocarbons

W 27-3W 46-11

W 86-29

W 13-3

W 14-24W 14-34

W 15-5

W 18-27

W 19-28

PA 21-34

PA 24-21

PA 32-29

PA 312-21

RMV 37-33

RMV 43-28A

GV 21-35

GV 25-27

GV 75-3

LANGSTAFF 109


17

1717

CASING HEAD CASING HEAD AND AND

PRODUCTION PRODUCTION GAS GAS

STABLE STABLE ISOTOPICISOTOPIC

COMPOSITIONCOMPOSITION

PICEANCE BASINPICEANCE BASIN

COMPOSITIONCOMPOSITIONNOT NOT

NECESSARILY NECESSARILY THE SAMETHE SAME

IMPLICATIONS?IMPLICATIONS?1818

WATER/MONITOR WELL SAMPLES FOR WATER/MONITOR WELL SAMPLES FOR COLLECTING NATURAL GAS ARE OF TWO TYPESCOLLECTING NATURAL GAS ARE OF TWO TYPES

FREE GASFREE GAS

FREE GAS COLLECTEDFREE GAS COLLECTED DISSOLVED GAS DISSOLVED GAS

FREE GASFREE GAS

DISSOLVEDDISSOLVED

GASGAS

1919

ADDRESSING DISSOLVED GAS ADDRESSING DISSOLVED GAS CONCENTRATIONCONCENTRATION

METHANE SOLUBILITY IS LOWMETHANE SOLUBILITY IS LOW

2020

DUPLICATE SAMPLESDUPLICATE SAMPLESMethod RSKMethod RSK--175175

SAMPLING VARIATIONSAMPLING VARIATION

Dissolved methane concentration in duplicateDissolved methane concentration in duplicatesamples varies by 9% samples varies by 9% plus or minusplus or minus 90 ug/L)90 ug/L)

Collected from water wells only Collected from water wells only

* ug/L = micrograms per liter or .001 milligrams per liter* ug/L = micrograms per liter or .001 milligrams per liter

SHORT TERM VARIABILTY ADDRESSED USINGSHORT TERM VARIABILTY ADDRESSED USINGMULTIPLE SAMPLES FROM SINGLE SITESMULTIPLE SAMPLES FROM SINGLE SITES

87 SAMPLE PAIRS87 SAMPLE PAIRS

CC11 Max = 0.55 + 1.14 * CMax = 0.55 + 1.14 * C11 MinMin

rr22 = 0.97= 0.97

DISSOLVED GAS COMPOSITION DISSOLVED GAS COMPOSITION AND HENRY’S LAWAND HENRY’S LAW

�� Dissolved gas phase composition obeys Henry’s Dissolved gas phase composition obeys Henry’s Law Law under equilibrium solution & exsolutionunder equilibrium solution & exsolution•• Partial pressure controls relative solubility of source gas Partial pressure controls relative solubility of source gas

in dissolved phasein dissolved phase

•• Gas Gas exsolvedexsolved in equilibrium with a headspace will reflect in equilibrium with a headspace will reflect relative concentration of free phase source gasrelative concentration of free phase source gasrelative concentration of free phase source gasrelative concentration of free phase source gas

•• Therefore gas ratios are useful for identifying source Therefore gas ratios are useful for identifying source gases in samples with dissolved gasgases in samples with dissolved gas

�� Free gas phaseFree gas phase•• Discharge of free gas driven by pressure gradient Discharge of free gas driven by pressure gradient

maintains chemical and isotopic composition of source maintains chemical and isotopic composition of source gasgas

�� Stable isotopes not affected by solution/Stable isotopes not affected by solution/exsolutionexsolution2323

USEFUL RATIOS FOR CROSS PLOTSUSEFUL RATIOS FOR CROSS PLOTS

�� [C[C11// Σ Σ CC11+] or [C+] or [C11/C/C22]] or [or [ CC11/C/C22+C+C33 ] or ] or

[C[C22+/+/ Σ Σ CC11+]+]

•• Susceptible to biogenic methane mixingSusceptible to biogenic methane mixing

�� CC22/C/C3 3 or Cor C22// Σ Σ CC22++�� CC22/C/C3 3 or Cor C22// Σ Σ CC22++

�� CC33// Σ Σ CC33++

�� Σ Σ CC44 isomers/isomers/ Σ Σ CC55 isomersisomers

�� Isomer ratiosIsomer ratios

•• iCiC44/nC/nC44

•• iCiC55/nC/nC55

2424

EXAMPLE GAS RATIO IN FREE GAS PHASE VS. DISSOLVEDEXAMPLE GAS RATIO IN FREE GAS PHASE VS. DISSOLVEDPHASE: SPATIAL/TEMPORAL CHANGES PHASE: SPATIAL/TEMPORAL CHANGES

MONITOR WELLSMONITOR WELLSTAPPING PLUMETAPPING PLUME

PLUMEPLUME

SOURCE GAS COMPOSITIONSOURCE GAS COMPOSITION

MWMW

MWMW

MWMW

MWMW

Down gradient directionDown gradient direction

of dissolved gas samplesof dissolved gas samples

In 4 monitor wellsIn 4 monitor wells

Bubbling seepsBubbling seeps

FREE GAS PHASE vs. DISSOLVED GAS PHASE FREE GAS PHASE vs. DISSOLVED GAS PHASE COMPOSITION : BUTANE ISOMERS OFFSETCOMPOSITION : BUTANE ISOMERS OFFSET

SOLUBILITY

MWMW

MWMW

MWMW

MWMW




PREFERENTIAL DISEQUILIBRIUM EXSOLUTION OF iC4

2626

mg/kgmmoles/kg

C1C2C3iC4nC4iC5nC5

24.41.52460.42.15762.41.41748.90.84361.41.05847.80.66338.50.534

SOLUBILITY

Source

STABLE ISOTOPES NOT FRACTIONATEDSTABLE ISOTOPES NOT FRACTIONATED


MWMW

MWMW

MWMW

MWMW




PLUMEPLUME

2727Source

STABLE ISOTOPE VARIABILITYSTABLE ISOTOPE VARIABILITY

PLUMEPLUME

GASGAS

RELEASERELEASE

2828

Stable isotope signaturesStable isotope signatures

Altered by mixing and oxidationAltered by mixing and oxidation

STABLE ISOTOPE SCATTER INCREASES WITH TIME STABLE ISOTOPE SCATTER INCREASES WITH TIME AND LOCATION DOWN GRADIENTAND LOCATION DOWN GRADIENT

MWMW

MWMW

MWMW

MWMW




PLUMEPLUME

±

2929


Source

MIXED GAS SOURCESMIXED GAS SOURCES

�� Biogenic methane ubiquitous in bedrock aquifersBiogenic methane ubiquitous in bedrock aquifers

•• >50 water wells with detectable dissolved methane>50 water wells with detectable dissolved methane

•• COCO22 reduction dominant reaction pathwayreduction dominant reaction pathway

�� Mixing affects gas ratios using methaneMixing affects gas ratios using methane

•• [C[C11// Σ Σ CC11+] or [C+] or [C11/C/C22]] or [or [ CC11/C/C22+C+C33 ] or [C] or [C22+/+/ Σ Σ CC11+]+]

�� Mixing affects stable isotope ratiosMixing affects stable isotope ratios

•• δδ1313C, D Methane more negativeC, D Methane more negative

•• δδ1313C, D Ethane more negativeC, D Ethane more negative

3030

COLORADO

NEW MEXICO

65% OF ALL SITES SAMPLED CONTAIN 65% OF ALL SITES SAMPLED CONTAIN

MEASURABLE AMOUNTS OF MEASURABLE AMOUNTS OF

DISSOLVED METHANEDISSOLVED METHANE3131

Denver Denver

SOURCE WELLSOURCE WELL

WELL 1WELL 1

WELL 2WELL 2

0 110 220 330 44055Feet

Basin Basin Case Case StudyStudy

UPDIPUPDIP

3232

CASE STUDY DENVER BASINCASE STUDY DENVER BASIN

Background Background

WELL 1WELL 1

WELL 2WELL 2

SOURCE WELLSOURCE WELL

Background Background

BIOGENICBIOGENIC

3333

OXIDATIONOXIDATION

�� Oxidation gradients set up within invaded zoneOxidation gradients set up within invaded zone

•• Well bore air/water interfaceWell bore air/water interface

•• Shallow alluvial sediment Shallow alluvial sediment vadosevadose//phreaticphreatic interfaceinterface

•• PhreaticPhreatic electron donor zoneselectron donor zones

�� Oxidation mediated by bacteriaOxidation mediated by bacteria

�� Observed temporal effects are rate dependentObserved temporal effects are rate dependent

•• Rate of bacterially mediated oxidation vs. Rate of Rate of bacterially mediated oxidation vs. Rate of

fresh gas deliveryfresh gas delivery

�� Preferential consumption of higher Preferential consumption of higher homologshomologs

�� Preferential consumption of straight chain isomersPreferential consumption of straight chain isomers

�� Preferential consumption of light isotopesPreferential consumption of light isotopes

3434

BUBBLING HYDROCARBONS CAN ACCELERATE BUBBLING HYDROCARBONS CAN ACCELERATE THE FOLLOWING NATURAL REACTIONS THE FOLLOWING NATURAL REACTIONS

+ COSOSO + Organics+ Organics --> Sulfide> Sulfide

AIRAIR

SulfuricSulfuric AcidAcid(corrosion)(corrosion)

+ CO2

+HardnessHardness

Mineral ScaleMineral ScalePRECIPITATIONPRECIPITATIONIncreasing SARIncreasing SAR

SOSO4 4 + Organics+ Organics --> Sulfide> Sulfide

AIRAIR

Rust StainRust StainPoor TastePoor Taste Dissolved Dissolved

IronIronIron SulfideIron SulfideGray ColorGray ColorPoor TastePoor Taste

DECREASING CONCENTRATION CHARACTERISITIC DECREASING CONCENTRATION CHARACTERISITIC OF HYDROCARBON OXIDATION OF HYDROCARBON OXIDATION

e.g. SAN JUAN BASIN e.g. SAN JUAN BASIN

3636

STABLE ISOTOPIC ENRICHMENT ASSOCIATED STABLE ISOTOPIC ENRICHMENT ASSOCIATED WITH BACTERIALLYWITH BACTERIALLY--MEDIATED OXIDATIONMEDIATED OXIDATION

QUADRATIC SURFACE

FIT TO CONCENTRATION

C1 mg/L899

Slope = 8.35

3737

5

6

7

8

Delta

13C

Pro

pane -

Delta 1

3C

Eth

ane

BACTERIALBACTERIALOXIDATION OXIDATION TRENDTREND

MULTIPLE SAMPLES OF DISSOLVEDMULTIPLE SAMPLES OF DISSOLVEDGASES IN CONTAMINATED WATER WELLGASES IN CONTAMINATED WATER WELL

CONSUMPTION RATES GREATER FOR CONSUMPTION RATES GREATER FOR PROPANE THAN FOR ETHANEPROPANE THAN FOR ETHANE

2

3

4

5

Delta

13C

Pro

pane -

Delta 1

3C

Eth

ane

2 3 4 5 6 7

C2/C3 (Vol %)

15*

15 1

16

162

Dietrich Production Bradenhead Soil Gas

TRENDTREND

WATER WELL

3838

TEMPORAL CHANGES IN COMPOSTION AND TEMPORAL CHANGES IN COMPOSTION AND STABLE ISOTOPES CORRELATEDSTABLE ISOTOPES CORRELATED

7

8

9

10

11

2

3

4

5

6

7

15-Apr-04 06-Oct-04 07-Dec-04 28-Mar-05 01-Jun-05 08-Sep-05 05-Dec-05 07-Mar-06 02-May-06

Date

Delta 13C C3-C2 (per mil) C2/C3 (Vol %)

REMEDIALREMEDIALCEMENT SQUEEZECEMENT SQUEEZE

3939

DILUTIONDILUTION

�� Screened intervals do not define water sourcesScreened intervals do not define water sources

•• Mixing via open hole or gravel pack commonMixing via open hole or gravel pack common

�� Mixing affects oxidation rates and dilutionMixing affects oxidation rates and dilution�� Mixing affects oxidation rates and dilutionMixing affects oxidation rates and dilution

•• Address remediation efficiency/ratesAddress remediation efficiency/rates

4040

PUMPING AND DRAWDOWN: PUMPING AND DRAWDOWN: WHERE DOES THE WATER COME FROM?WHERE DOES THE WATER COME FROM?

PUMP

PUMP

4141

PRINCIPAL COMPONENTS OF GROUNDWATER IN ROCKIESPRINCIPAL COMPONENTS OF GROUNDWATER IN ROCKIES

LIME : CALCIUM ANDLIME : CALCIUM AND

MAGNESIUM BICARBONATEMAGNESIUM BICARBONATE

GYPSUM GYPSUM ––

CALCIUM SULFATE CALCIUM SULFATE

SILTSILT

SANDSTONESANDSTONE

SODIUM BICARBONATESODIUM BICARBONATE

SODIUM CHLORIDESODIUM CHLORIDE

THERNARDITE THERNARDITE ––

SODIUM SULFATE SODIUM SULFATE

CALCIUM SULFATE CALCIUM SULFATE

SANDSTONESANDSTONE

SILTSILT

COALCOAL

COALCOAL4242

10

15

20

GPM

RELATIVE AMOUNTS OF WATER FROM EACH RELATIVE AMOUNTS OF WATER FROM EACH SOURCE CAN CHANGESOURCE CAN CHANGE

METHANE CONCENTRATION


0

5

10GPM

M J J A S O N D J F M A M

Months of the Year

Deep Source Shallow Source

Deep methane sourceDeep methane source



4343

TIME SERIES OF TIME SERIES OF WATER WELL WATER WELL

DATA DATA FROM A SINGLE FROM A SINGLE

WELLWELL

WHAT IS THEWHAT IS THEBEST PLOTTINGBEST PLOTTINGPARAMETER?PARAMETER?PARAMETER?PARAMETER?

4444

DISSOLVED METHANE CONCENTRATION VARIESDISSOLVED METHANE CONCENTRATION VARIESLINEARLY WITH % CHLORIDELINEARLY WITH % CHLORIDE

10

12

14

16

Dis

solv

ed

Me

than

e (

mg

/L)

27-May-04

03-Jun-04

09-Jun-04 17-Jun-04

24-Jun-04

30-Jun-04

07-Jul-04

15-Jul-0421-Sep-04

03-Nov-04

03-Nov-04

DUPLICATEDUPLICATE

DUPLICATEDUPLICATESAMPLESSAMPLES

0

2

4

6

8

Dis

solv

ed

Me

than

e (

mg

/L)

60 65 70 75 80 85 90 95 100

% Chloride

07-Mar-03

04-Aug-04

21-Sep-04

21-Sep-04

DUPLICATEDUPLICATESAMPLESSAMPLES

4545

CONCLUSIONSCONCLUSIONS

�� Gas ratios and stable isotopes most useful for Gas ratios and stable isotopes most useful for

identifying gas well point sourcesidentifying gas well point sources

•• Differentiate free and dissolved gas samplesDifferentiate free and dissolved gas samples

�� Immediate sampling is bestImmediate sampling is best

•• Sample producing wells and casing head gas within Sample producing wells and casing head gas within

½ mile radius down dip or along strike of discharge½ mile radius down dip or along strike of discharge

�� Use repeated sampling to examine remediation, Use repeated sampling to examine remediation,

and effects of oxidation and dilutionand effects of oxidation and dilution

•• Always standard set of water quality analytes both Always standard set of water quality analytes both

inorganic and organicinorganic and organic

�� Baseline sampling essential to support forensicsBaseline sampling essential to support forensics

•• Abandoned wellsAbandoned wells

•• Historical contaminationHistorical contamination 4646

Anthony W. Gorody, Ph.D., C.P.G., P.G. Anthony W. Gorody, Ph.D., C.P.G., P.G.

PresidentPresident


QUESTIONS AND ANSWERSQUESTIONS AND ANSWERS


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FACTORS AFFECTING FORENSIC ANALYSIS AND · PDF file · 2010-10-25factors affecting...

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