Cement Bond Log

Exploration Technique: Cement Bond Log

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Exploration Technique Information
Exploration Group:	Downhole Techniques
Exploration Sub Group:	Well Log Techniques
Parent Exploration Technique:	Acoustic Logs
Information Provided by Technique
Lithology:
Stratigraphic/Structural:
Hydrological:
Thermal:
Cost Information
Low-End Estimate (USD):	0.850.85 TUSD 0.85 MUSD 0.85 kUSD 85 centUSD / foot
Median Estimate (USD):	1.251.25 TUSD 1.25 MUSD 1.25 kUSD 125 centUSD / foot
High-End Estimate (USD):	3.003 TUSD 3 MUSD 3 kUSD 300 centUSD / 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

Cement Bond Log:

A representation of the integrity of the cement job, especially whether the cement is adhering solidly to the outside of the casing. The log is typically obtained from one of a variety of sonic-type tools. The newer versions, called cement evaluation logs, along with their processing software, can give detailed, 360-degree representations of the integrity of the cement job, whereas older versions may display a single line representing the integrated integrity around the casing.

Other definitions:Wikipedia Reegle

Introduction

Cement-bond logging usually employs a single receiver to obtain information on the quality of the bond between casing and cement and between cement and borehole wall. Most cement-bond logs are a measurement only of the amplitude of the early arriving casing signal. Although a small amount of the total acoustic energy may be received from the rock when the casing is free to vibrate, the formation signal usually is not detectable. The detection of channeling through cement in the annular space is one of the main objectives of cement-bond logging. The fundamental principle is that the acoustic signal will be more attenuated in the presence of cement than if the casing were uncemented.

Use in Geothermal Exploration

A cement bond log can be done to test the integrity of a geothermal exploration well.

Related Techniques

Acoustic/Sonic log

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.

Environmental Mitigation Measures

Cement bond logs are required to evaluate the isolation and protection of usable mineral resources, ground water aquifers. This protection an isolation is generally required in federally approved wells to a depth of 2,000' in non geothermal wells. Geothermal wells are cemented behined each casing string.

Data Access and Acquisition

A circuit is employed to convert the difference in time of arrival of the P-wave at the two detectors to transit time (t) in ms/ft.

Best Practices

Analysis and interpretation of a cement bond log is necessary to assure integrity of the cement job, and if an adequate bond is not present throughout the interval the drilling contractor will be required to place plugs and perforate the casing and squeeze cement (perf and squeeze) into the zone. A cement bond log is required to determine whether the perf and squeeze was effective.

Potential Pitfalls

Even expert analysis of a cement-bond logs will not always locate all channels through the cement accurately.

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. A cement bond log is required to determine whether there is an adequate bond between the casing and well bore. if the analysis of the cement bond logs indicates that the seal is not adequate the drilling contractor will be required to per and squeeze the zone prior to continuing operations.

References

EPA-Environmental Geophysics-Geophysical Methods-Acoustic Logging

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Cement Bond Log

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Exploration Technique: Cement Bond Log