[PDF] sloto_geophysical_characterizati

34870_7sloto_geophysical_characterization_and_borehole_geophysical_tools_to_aid_monitor_well_placement_and_completion.pdf

U.S. Department of the Interior

U.S. Geological Survey GEOPHYSICAL

CHARACTERIZATION AND

BOREHOLE GEOPHYSICAL TOOLS

TO AID MONITOR WELL

PLACEMENT AND COMPLETION Ron Sloto

U.S. Geological Survey

Pennsylvania Water Science Center

ƒBorehole geophysics is the collection of

geologic and hydrologic information in wells by lowering and raising probes on a wire ƒMuch more can be learned by the analysis of a suite of geophysical logs as a group than by the analysis of the same logs individually

GEOHYDROLOGIC

CHARACTERIZATION

ƒFractures and water-bearing zones (location

and orientation)

ƒStructural features

ƒLithology and lithologic contacts

ƒAquifer hydraulic characteristics

ƒGroundwater flow system

ƒHydraulic head differences

ƒWell construction

For new monitor wells

ƒProper location to set well screen

ƒAquifer characteristics

ƒHydraulic connections between monitor

wells BOREHOLE GEOPHYSICS

BOREHOLE GEOPHYSICS

For existing (domestic) wells

ƒWell construction characteristics

(depth, casing length, water-bearing zones)

ƒAquifer hydraulic characteristics

ƒWater quality

BOREHOLE GEOPHYSICS

STANDARD LOG SUITE

ƒCaliper

ƒNatural gamma

ƒSingle-point electric

ƒFluid resistivity

ƒFluid temperature

ƒFlowmeter

ƒTelevision

ƒAcoustic televiewer

USGS Pennsylvania Water

Science Center Logger

Provides a continuous record of average borehole diameter Used to identify fractures, water-bearing openings, and changes in lithology CALIPER LOG 0 50
100
150
200
250
300
350
400
450
500
5 D E P T H , I N F E E T B E L O W L A N D S U R F A C E 10 15 20 5 10 15 20 550

GAMMA LOG

Records the natural- gamma radiation emitted from rocks penetrated by the borehole. The gamma log often is used to define lithology and correlate geologic units between boreholes. Caliper and natural-gamma logs of well BK-2202, Bridgetown Township, northern Bucks County.050 100 150 2005.5 6 6.5 70 20 40
60
80
100
120
140
1600
20 40
60
80
100
120
140

160DIABASE

BRUNSWICK

GROUPHOLE DIAMETER,

IN INCHESNATURAL GAMMA, IN

COUNTS PER SECONDDEPTH, IN FEET BELOW LAND SURFACE Electrical resistance increases with grain size and decreases with borehole diameter, density of water-bearing fractures, and increasing dissolved-solids concentration of borehole fluid SINGLE-POINT RESISTANCE

ELECTRIC LOG 6

HOLE DIAMETER,

IN INCHESNATURAL GAMMA,

COUNTS PER SECONDSINGLE POINT RESISTANCE

IN OHMS

810110 1002,000 4,000 6,000 8,000DEPTH, IN FEET BELOW LAND SURFACE

0 50
100
150
200
250
300
350
400
500

450STOCKTON

FORMATION

PALEOSOL

CARBONATE

ROCK FLUID TEMPERATURE LOG Provides a continuous record of the temperature of the fluid in the borehole. FLUID RESISTIVITY LOG Measures the electrical resistance (fluid conductivity) of fluid in the borehole.

Logs reflect changes in the dissolved-solids

concentration of the borehole fluid. l 5.0 l 2.9 l 1.2 l 0.7 HOLE DIAMETER,

IN INCHES

7 0 50
100
150
200
250
350
D E P T H , I N F E E T B E L O W L A N D S U R F A C E

FLUID TEMPERATURE,

IN DEGREES CELSIUS FLUID RESISTIVITY,

IN OHM-METERS

9 11 450
12 12.5 13 150 450 300 300
400
WELL BK-1845, WARMINSTER TOWNSHIP, BUCKS COUNTY FLUID

TEMPERATURE

AND FLUID

RESISTIVITY

LOGS Where would

you set the screen?

HEATPULSE FLOWMETER

Measures rate and direction

of borehole flow under static conditions Measures contribution of individual fractures under pumping conditions

Differences in hydraulic head

Delineates transmissive fractures

Defines relative vertical hydraulic

gradients

CALIPER LOG HOLE

DIAMETER, IN

INCHES 8 16 8 10 12 14 0

400
50
100
150
200
250
300
350
D E P T H , I N F E E T B E L O W L A N D S U R F A C E BOREHOLE TELEVISION

VERTICAL FRACTURE IN WELL AT 138

FEET BELOW TOP OF CASING

BOREHOLE TELEVISION

Corehole in Marcellus Shale Play

The acoustic borehole televiewer log is a magnetically oriented, 360, photograph-like image of the acoustic reflectivity of the borehole wall. Digital images from the televiewer are recorded by the computer collecting logging data. Televiewer logs indicate the location and strike and dip of fractures and lithologic contacts ACOUSTIC TELEVIEWER N E S W N

Projected

N S

WE 3-D NAWC SUPPLY WELL 3 BOREHOLE

DEVIATION STRUCTURAL

ORIENTATION

BOREHOLE FLUID SAMPLER

Wireline sampler

Captures borehole fluid

from a discrete depth

Largest sampler

collects up to 1 liter of fluid

AQUIFER-ISOLATION (PACKER) TESTS

Isolation of individual

fractures or fracture zones Hydraulic properties with depth (K, specific capacity)

Hydraulic connections

ƒAround borehole

ƒTo other boreholes

Discrete-depth water samples

ANALYSIS OF A SUITE OF BOREHOLE

GEOPHYSICAL LOGS