Strategies for Characterizing Strategies for Characterizing Shallow Soil Gas FluxShallow Soil Gas Flux

and Chemistry, and Chemistry, BlanBlan Farm, Hancock County, Ky.Farm, Hancock County, Ky.

Investigators:Investigators:

Marty Parris and Michael P. SolisMarty Parris and Michael P. Solis

Kentucky Energy and Environment Cabinet, Kentucky Energy and Environment Cabinet, UK Environmental Research and Teaching UK Environmental Research and Teaching

Laboratory, Laboratory, IsotechIsotech LaboratoriesLaboratoriesPenn State UniversityPenn State University

Monitoring, Mitigation, and Monitoring, Mitigation, and Verification (MMV)Verification (MMV)

MMVMMV——portfolio of geophysical, geochemical, portfolio of geophysical, geochemical, geological, and engineering techniques used geological, and engineering techniques used to accurately document the fate of COto accurately document the fate of CO22injected into subsurface reservoirs.injected into subsurface reservoirs.DOEDOE’’ss perspectiveperspective——successful successful sequestration means that 99% of injected sequestration means that 99% of injected COCO22 remains in the reservoir for geologically remains in the reservoir for geologically significant time periods.significant time periods.““For surface and nearFor surface and near--surface soil gas surface soil gas measurements to be effective as an MMV measurements to be effective as an MMV tool, need to understand natural carbon tool, need to understand natural carbon cycle and its variability.cycle and its variability.”” (GEO(GEO--SEQ, 2004)SEQ, 2004)

Develop preDevelop pre--injection database injection database characterizing atmospheric, biologic, and characterizing atmospheric, biologic, and geologic (microseepage) contributions to geologic (microseepage) contributions to soil gas flux and chemistrysoil gas flux and chemistryUse database to resolve anomalies, if any, Use database to resolve anomalies, if any, during injection and postduring injection and post--injection phasesinjection phasesEvaluate influence of basin specific factors Evaluate influence of basin specific factors on soil gas flux and chemistry, e.g. shallow on soil gas flux and chemistry, e.g. shallow coals and reclaimed mine landscoals and reclaimed mine landsThe challenge: resolve microseepage signal The challenge: resolve microseepage signal << biologic and atmospheric signal<< biologic and atmospheric signal

Soil Gas Chemistry ObjectivesSoil Gas Chemistry Objectives

BlanBlan Farm Geologic SettingFarm Geologic Setting

++

+

++ +

1000 ft

Shallow (< 1 m) MeasurementsShallow (< 1 m) Measurements

Shallow Soil Gas ChemistryShallow Soil Gas ChemistryMeasured bulk (COMeasured bulk (CO22, CH, CH44, C, C22HH66, , CC33HH88) and carbon isotopic ) and carbon isotopic composition (composition (δδ1313CC--COCO22))Duplicate measurements per Duplicate measurements per location at 30, 60, 100 cmlocation at 30, 60, 100 cmBulk and isotopic atmospheric Bulk and isotopic atmospheric composition also measuredcomposition also measuredCharacterize season variation and Characterize season variation and anthropomorphic influencesanthropomorphic influences

Shallow Soil Gas ChemistryShallow Soil Gas Chemistry

Collecting soil gases in Robinson Forest, fall 2005Collecting soil gases in Robinson Forest, fall 2005

Soil Gas FluxSoil Gas FluxMeasure fluxes using closed chamber Measure fluxes using closed chamber methodmethodCOCO22 flux measured directly w/ flux measured directly w/ LicorLicor LILI--8100 equipped w/ infrared gas analyzer8100 equipped w/ infrared gas analyzerCHCH44 flux determined indirectly by flux determined indirectly by measuring change in chamber measuring change in chamber composition w/ timecomposition w/ timeTriplicate flux measurements per Triplicate flux measurements per location to capture variabilitylocation to capture variability

Soil Gas FluxSoil Gas Flux

Temperature Probe

Optical bench w/Infrared analyzer

FluxChamber

Average W06, S06 Soil Gas COAverage W06, S06 Soil Gas CO22

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000

CO2 Concentration (ppmv)

Dep

th (c

m)

Avg. Atmospheric CO2= 425±28 ppmv

Summer—163,424 ppmv

Winter—48,593 ppmv

Reclaimed mine land

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

0 0.5 1 1.5 2 2.5 3 3.5 4

Average W06, S06 Soil Gas CHAverage W06, S06 Soil Gas CH44

CH4 Concentration (ppmv)

Dep

th (c

m)

Avg. Atmospheric CH4= 1.94±0.03 ppmv

Summer—25 ppmv

Winter—7.6ppmv

Reclaimed mine land

COCO22 and CHand CH44 FluxesFluxes

Positive COPositive CO22 fluxes measured at all locationsfluxes measured at all locationsSummer (avg.= 15.7Summer (avg.= 15.7±±6.2 grams/m6.2 grams/m22/day, n= /day, n= 84) > winter (avg.= 4.684) > winter (avg.= 4.6±±0.8 grams/m0.8 grams/m22/day, /day, n=83)n=83)For CHFor CH44, most chamber locations (65%, n= , most chamber locations (65%, n= 106) showed no consistent decrease or 106) showed no consistent decrease or increase w/ timeincrease w/ time28% (n= 46) showed negative CH28% (n= 46) showed negative CH44 flux (avg.= flux (avg.= 1.691.69±±1.5 grams/m1.5 grams/m22/day)/day)7% (n= 11) showed positive CH7% (n= 11) showed positive CH44 flux (avg.= flux (avg.= 1.311.31±±1.4 grams/m1.4 grams/m22/day)/day)

Soil Gas AnomaliesSoil Gas Anomaliesand Microseepageand Microseepage

Positive CHPositive CH44 fluxes in oxidized soilsfluxes in oxidized soilsSoil gas CHSoil gas CH44 concentrations concentrations consistently > atmospheric in oxidized consistently > atmospheric in oxidized soilssoilsEnriched Enriched δδ1313CC--COCO22 values relative to values relative to atmosphereatmosphere--soil organic matter mixing soil organic matter mixing linelinePresence of light hydrocarbons (e.g. Presence of light hydrocarbons (e.g. CC22HH66, C, C33HH88))

Reclaimed Mine Lands and MMVReclaimed Mine Lands and MMV

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

100 1000 10000 100000

Avg. 100 cm Bulk TOC

Avg. Atmosphere

Reclaimed mine land Avg. 100 cm Bulk TIC

CO2 Concentration (ppmv)

δ13 C

-CO

2 (‰

, PD

B)

Eastern Ky conventionalreservoir gas