Field Observations On The Use Of The Cement Bond Log And Its Application To The Evaluation Of Cementing Problems
Authors: Flournoy R.M. , Feaster J.H. 
Published: December 2007

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This paper was prepared for the 38th Annual Fall Meeting of the Society of Petroleum Engineers of AIME in New Orleans, La., on October 6–9, 1963, and is considered the property of the Society of Petroleum Engineers. Permission to published is hereby restricted to an abstract of not more than 300 words, with no Illustrations, unless the paper is specifically released to the press by the Editor of the Journal of Petroleum Technology or the Executive Secretary. Such abstract should contain conspicuous acknowledgement of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request providing proper credit is given that publication and the original presentation of the paper.
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Abstract
This paper presents various observations arising from the use of the cement bond log in the offshore Louisiana area. most of these observations relate to log usuage in evaluating the relative merits of various cementing practices and techniques. Also included are several pertinent observations on log response and interpretation.

Introduction
The cement bond log (CBL) has been in field use for over three years. This tool has provided, for the first time, a definite qualitative evaluation, foot by foot, of the entire cement column in place behind the casing. Previous cement evaluation methods depended to a large extent upon assumptions and theoretical calculations applied to a single actually investigated criterion - the top of the cement column.
Acceptance of this new tool has been relatively slow and painful; painful in the realization of just how poor many of our cement jobs were, particularly in deviated wells. The CBL has in some instances revealed primary cementing results differing markedly from what our previous conceptions indicated they should be; a situation largely responsible for initial reservations concerning the tool and the validity-of the log. However, subsequent observations of the logos correct or logical response to various known or otherwise substantiated aspects of cementing results have alleviated our doubts as to the ability of the log to accurately indicate in-place cement quality through the medium Of the bond between the cement and the casing. Primary among these observations to which we refer are (1) verification by temperature log of the location of a cement column top as indicated by the CBL, (2) the CBL response to specific cement conditions such as at stage collars in multistage cementing and in squeeze cemented areas, and (3) CBL repeatability when run for both the primary cement job and a subsequent squeeze job, outside of the area affected by the squeeze.
Evaluation of a cement job by the CBL usually follows two separate channels of investigation:
precise evaluation of cement quality in specific intervals associated with productive zones, and overall quality of cementation, i.e., the degree and percentage of bonding throughout the entire cemented area. It is the first of these with which we are primarily concerned in the evaluation of the individual cement job.
The second forms the basis on which we may compare one cement job with another for the Purpose of evaluating variations in cementing practices and techniques.