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)