Caliper Log

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Exploration Technique: Caliper Log

Exploration Technique Information
Exploration Group: Downhole Techniques
Exploration Sub Group: Well Log Techniques
Parent Exploration Technique: Well Log Techniques
Information Provided by Technique
Cost Information
Low-End Estimate (USD): 0.4040 centUSD
4.0e-4 kUSD
4.0e-7 MUSD
4.0e-10 TUSD
/ foot
Median Estimate (USD): 0.7878 centUSD
7.8e-4 kUSD
7.8e-7 MUSD
7.8e-10 TUSD
/ foot
High-End Estimate (USD): 3.00300 centUSD
0.003 kUSD
3.0e-6 MUSD
3.0e-9 TUSD
/ foot
Time Required
Low-End Estimate: 0.35 days9.582478e-4 years
8.4 hours
0.05 weeks
0.0115 months
/ job
Median Estimate: 0.46 days0.00126 years
11.04 hours
0.0657 weeks
0.0151 months
/ job
High-End Estimate: 0.69 days0.00189 years
16.56 hours
0.0986 weeks
0.0227 months
/ job
Additional Info
Cost/Time Dependency: Depth, Temp, Resolution
Caliper Log:
A caliper log is a well logging tool that provides a continuous measurement of the size and shape of a borehole along its depth and is commonly used in hydrocarbon exploration when drilling wells. The measurements that are recorded can be an important indicator of cave ins or shale swelling in the borehole, which can effect the results of other well logs.
Other definitions:Wikipedia Reegle

A caliper log provides a representation of the diameter of a borehole along its depth. Wellbores are usually irregular in diameter, it is important to have a tool such as the caliper log that measures diameter at multiple locations. The drilling engineer will use the caliper measurement as a qualitative indication of both the condition of the wellbore and the degree to which the mud system has maintained hole stability. This is also critical information when calculating the cement volume when the casing is cemented. Caliper logs can also give some indication of formation types and whether or not the rocks are hard and compact or loose gravel.

Field Procedures
The geophysical/well logging service company conducts the down hole logging operation and produces both digital and hard copy logs. The Drilling contractor trips the drill pipe and bit and conditions the well bore for logging.

Data Access and Acquisition
Caliper logs are usually measured mechanically, with only a few using ultrasonic devices which provide full azimuthal coverage with high resolution. The tools measure diameter at a specific chord across the well.
Best Practices
A single axis caliper provides a single diameter at a specific chord across the borehole. A multi-axis caliper has multiple arms and can measure the diameter of the well bore in multiple locations simultaneously. This provides useful information as to the shape of the borehole and when run in conjunction with a orientation tool can give understanding to the stress orientation.
Potential Pitfalls
An unstable well bore (sluffing, wash outs, etc) can be of concern in any well logging operation. In extreme condition, the loss of the logging tool down hole could possibly result in the loss of the hole and would require premature abandonment or the necessity to side track to complete the well drilling operation.

NEPA Analysis
Well logging is a standard operation associated with the drilling permit approval and is included in the down hole analysis of the drilling program.

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