geophysics at the borehole and cross-borehole … at the borehole and cross-borehole scale carole...
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Geophysics at the borehole and Geophysics at the borehole and crosscross--borehole scaleborehole scale
Carole Johnson, John Lane Carole Johnson, John Lane and John Williamsand John Williams
OGWOGW--Branch of GeophysicsBranch of Geophysics
Overview
• Historical data and Geologic maps• Surface geophysics• Borehole geophysics• Cross-hole Testing • Hydraulic Measurements hydraulic
testing, water levels, sampling, pumping tests
• Integration and iteration
Historical applicationof surface geophysics
Electromagnetics (EM)• Conductive fluids in overburden and
shallow bedrock
Seismic Refraction• Saturated thickness
and bedrocktopography
Shallow conductive anomalies
EM61
GPR and GPS
EM31
Seismic reflection Ground penetrating radar (GPR)
• Subsurface stratigraphy • Bedrock topography
Surface geophysicsSurface geophysics
Surface geophysicsSurface geophysics
Electromagnetics (EM)• Sheet-like conductive fluids or layers
in bedrockDC resistivity profiling
• Subsurface bedrock structureAzimuthal square-array resistivity
• Bedrock anisotropy – fractures and/ or lithology
0 200 400-550
-450
-350
-250
-150
-50
DIS
TA
NC
E, I
N F
EE
T
DISTANCE, IN FEET
0
-18
30
Well B13
EM 34 anomalyEM 34 anomaly30º
Modeling 2D Resistivity DataModeling 2D Resistivity DataInverted Resistivity Section
Forward Model
Inverted Resistivity Section of Forward Modeled
Synthetic Data
RES2DINV (Loke, 1997)
Conductive anomaly
OverburdenWetland
Till / weathered bedrock
RES2DMOD (Loke, 1997)
Borehole geophysicsBorehole geophysics
Characterize hydrogeology in and surrounding the borehole
• Conventional logs• Acoustic televiewer• Optical televiewer
• Radar• Borehole flowmeter• Hydraulic and geochemical testing
VIRGINIA COASTAL PLAIN
Sand
Fining upSand to Clay
Coarsening up Clay to Sand
Sand
EM CONDUCTIVITY LOGS AND DISSOLVED CHLORIDESGreat Neck, Long Island
Sea level
250
125
ft
13,00012,500
13
18
Sand and gravel Silt and clay Bedrock
Freshwater-Saltwater Interface
Confining Unit
62 ft
64 ft
Evaluate orientation of hydraulically active fracture sand structure at the field scale and site scale
CrossCross--hole geophysicshole geophysics
Radar tomography - 30 to 100m
Resistivity tomography – up to100 m
Seismic tomography – 10 to 1 km
VELOCITY ATTENUATION
HIGH
LOWMW73 MW73MW74 MW74
DE
PT
H, I
N F
EE
TRADAR
VELOCITY ATTENUATION
HIGH
LOWMW73 MW73MW74 MW74
DE
PT
H, I
N F
EE
TRADAR
FSE Well Field Site Map& Tracer Injection Method
FSE-4 FSE-3
FSE-2 FSE-1
Injection
Extraction
~9m
~13m
Extraction Injection
Packers
Pump
PVC CorePipe
Tracer
Difference Tomograms
17 Hrs 37 Hrs
Hydraulic evaluationHydraulic evaluation
Conventional single hole flowmeter logging – ambient and pumping conditions (flow prevention)
• Discrete interval hydraulic testing -pumping or injection conditions
• Discrete interval geochemical sampling• Discrete interval, long-term head
monitoring• Cross-hole flowmeter logging
CROSSHOLE TRANSIENT FLOWMETER MEASUREMENTS
Paillet (2001)
Paillet(2001)
CROSSHOLE TRANSIENT FLOWMETER MEASUREMENTS
FSE WELL FIELD
• Seismo-electric effect – work proposed by Ellefsen, and others
• Borehole stress measurements –evaluation of the stress field from induced fractures in boreholes(Hickman and others)
With concurrent tomographic diff-erencing methods (Lane and Wright)
Research TopicsResearch Topics
Hydraulic fra
cture
hmin
Hmaxx-section of well
0 10 20 30 METERS
• 2D-Azimuthal resistivity – before and after pumping to evaluate anisotropy and potentially contributing recharge area
•0
•1000
•2000
•3000
•4000•2
•17•32
•47•62
•77
•92
•107
•122•137
•152•167
•182•197
•212•227
•242
•257
•272
•287
•302•317
•332•347
•APPARENT RESISTIVITIES,•IN OHM-METERS
•AZIMUTH, IN DEGREES
Research topics Research topics -- continuedcontinued
Surface to boreholeSurface to borehole
• Borehole to surface measurements –Resistivity, EM, and Seismic (tube waves)
• Surface or borehole NMR may be useful•
• Identify correlations with surrogate data. Collect surrogate data, such as tomography data and hydraulic data and combine geostatistically (soft kriging or anealing process, Day-Lewis)
Research topicsResearch topics–– continuedcontinued
USGS Long Beach Pier C Test Well
800 ft
900 ft
GAMMA LITHOLOGY
3D Data collection and 3D Data collection and processingprocessing
• 2-D and 3-D resistivity
• 3-D Radar (Mark P. Grasmueck, RSMAS University of Miami)
• Seismic reflection
Research topicsResearch topics–– continuedcontinued
2D resistivity in a 3-D Fence Diagram
Example from Chris Braun ABF in Fort Worth, TX
3D representation ofinverted resistivityvalues along fourhorizontal planesat elevations of 192,190, 188, and 186 m.
Braun, Dodec 2001
10 m
3-D Radar ApplicationGrasmueck
10 m
3-D GPR Survey Outline
3-D Ground Penetrating Radar Acquisition
Survey lines every 10 cm
3-D GPR
Grasmueck,1996
3-D GPR
Grasmueck, 1996
Interpretation Needs• Integrate data over various scales
• Upscaling: Integrate data from multiple disciplines, including geologic mapping, geochemical data – NAWQA, isotope dating
• Assess transferablility: Can data collected at multiple sites be statistically or geostatistically meaningful? Is the measurement parameter meaningful, and at what scale?
Measurements at Regional Scale
Remote sensing:• Thematic mapping• Airborne EM• Temperature –
non urban areas
• Seismic Reflection: 1 Kilometer deep and apart (Odum)