This document discusses caliper logs, which measure the size and shape of a borehole. It describes different types of caliper tools, including multi-finger, dual caliper, and ultrasonic caliper tools. The document explains that caliper logs provide information about borehole shape and volume, mud cake buildup, lithology, and cement volume. More arms on a caliper tool provide more accurate measurements of borehole cross-section and shape. Caliper logs are often run with acoustic or neutron-density logs.

1. PETE-303: Well Logging
Spring 2016
Week #02
Eng. Khaled Abdelgawad
Department of Petroleum Engineering
KFUPM ENGINEERING
Well Logging
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2. Caliper Log

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Passive Measurements
Caliper
Spontaneous Potential
Gamma Ray

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Caliper Log 4
Continuous measurement of the size and
shape of a borehole along its depth.
Measures the variation in borehole diameter
as it is withdrawn from the bottom of the
hole, using two or more articulated arms that
push against the borehole wall
Arms
Bit Size
Multifinger
Tool
4 Arms
Caliper
3 Arms
Caliper
Dualcaliper

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Caliper Log 5
Continuous measurement of
the size and shape of a
borehole along its depth.

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Why Caliper Log?
Borehole Shape and volume
Environmental correction
Quantitative interpretation
Cement Volume calculation
Push a section of a probe against the side of the borehole
Indicate build-up of mud cake.
Selection of consolidated formations
Borehole breakout analysis
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Log Presentation 7
Borehole
Volume
Ticks (ft3)

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Caliper configurations
The more arms, the more accurate the
measurement of the shape and cross-
sectional area of the wellbore.
Caliper logs are usually run simultaneously
with an acoustic or a neutron-density log.
An average hole diameter is calculated and
recorded.
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Caliper Interpretation
Hole volumes
- In general, more arms give better accuracy
- Two arms < 100% error
- Three arms < 20% error
Mud cake
- If dcaliper < dbit
- hmc = (dbit - dcaliper)/2
Lithology
- Shales may indicate borehole enlargement
- Spikey curve may indicate fractures
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Caliper configurations
A one-arm device caliper and three-arm
bow-spring device caliper obtained in
the same borehole interval.
How to explain the disagreement ?!
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Different Caliper logs 11
CALN Compensated Neutron Caliper (Diameter)
CALD Litho Caliper (Diameter)
CALM Micro Spherically Focused Tool Caliper (Diameter)

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Different Caliper logs 12

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Different Caliper logs 13

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Caliper Log Interpretation 14
ℎ 𝑚𝑐 =
𝑉ℎ =
𝑉𝑐𝑒𝑚𝑒𝑛𝑡 =

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Dipmeter Tool 15

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Caliper Log Interpretation
Types of enlarged borehole and their caliper log response
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Four-arm caliper -Example
Four-arm caliper log plot
displaying borehole breakouts
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Ultrasonic caliper
Using high-frequency acoustic signals.
A transducer emits a high-frequency pulse that
is reflected by the pipe or borehole wall and
received by the transducer.
The diameter is determined from the time of
flight of this echo and the fluid acoustic
velocity.
The transducer is rotated to produce a cross
section of the borehole size and full-coverage
images of the borehole wall.
The measurement has high resolution and is
used to detect deformations, the buildup of
scale, or metal loss due to corrosion.
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Standoff (d) = (vmt)/2
Dh = Dt + 2d
3-D internal
diameter
caliper
image

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Ultrasonic caliper 19
Standoff (d)=(vmt)/2
Dh = Dt+2d