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
Borehole geophysics is the collection of
geologic and hydrologic information in
wells by lowering and raising probes on
a wire
Much 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
Fractures and water-bearing zones (location
and orientation)
Structural features
Lithology and lithologic contacts
Aquifer hydraulic characteristics
Groundwater flow system
Hydraulic head differences
Well construction
• For new monitor wells
Proper location to set well screen
Aquifer characteristics
Hydraulic connections between monitor
wells
BOREHOLE GEOPHYSICS
BOREHOLE GEOPHYSICS
• For existing (domestic) wells
Well construction characteristics
(depth, casing length, water-bearing
zones)
Aquifer hydraulic characteristics
Water quality
BOREHOLE GEOPHYSICS
STANDARD LOG SUITE
Caliper
Natural gamma
Single-point electric
Fluid resistivity
Fluid temperature
Flowmeter
Television
Acoustic 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.
0 50 100 150 2005.5 6 6.5 70
20
40
60
80
100
120
140
160
0
20
40
60
80
100
120
140
160
DIABASE
BRUNSWICKGROUP
HOLE DIAMETER,
IN INCHES
NATURAL GAMMA, IN
COUNTS PER SECOND
DE
PT
H,
IN F
EE
T B
EL
OW
LA
ND
SU
RF
AC
E
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 INCHES
NATURAL GAMMA,
COUNTS PER SECOND
SINGLE POINT RESISTANCE
IN OHMS
8 10 1 10 100 2,000 4,000 6,000 8,000
DE
PT
H,
IN F
EE
T B
EL
OW
LA
ND
SU
RF
AC
E
0
50
100
150
200
250
300
350
400
500
450
STOCKTONFORMATION
PALEOSOL
CARBONATEROCK
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
W
E3-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
Around borehole
To other boreholes
• Discrete-depth water
samples
ANALYSIS OF A SUITE OF BOREHOLE
GEOPHYSICAL LOGS
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