Cement Bond Logging - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 192

Various additives are commonly used with cements to control such variables as
density, viscosity, setting time, and compressive strength. Table 12.2 details the
effects of additives on cements.
Other practices commonly used during cementing operations include the use of
casing centralizers, scratchers (to remove mudcake from the borehole wall), and
turbolizers (to induce turbulent fl ow in the casing/formation annulus).
The use of cement additives and/or mechanical accoutrements can dramatically
affect the quality of the fi nal cement job. Anything, within reason, that assists in
obtaining a good hydraulic seal should not be overlooked.
Table 12.2 Effects of some additives on the physical properties of cement
Note : Reprinted with permission of Halliburton Services
Denotes minor effect
Denotes major effect and/or principal purpose for which used
* Small percentages of sodium chloride accelerate thickening
Large percentages may retard API class A cement
Principles of Cement Bond Logging
Conventional CBL tools rely for their operation on the fact that a compressional
(acoustic) wave transmitted along the wall of a steel pipe becomes attenuated if the
pipe has cement bonded to it. The relationship between the compressive strength of
the cement and the attenuation rate (measured in db/ft) is shown in Fig. 12.3 . Note
that the type of cement is relatively unimportant and that, given the attenuation rate,
a cement compressive strength can be deduced.