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