CBL was firstly design in 1960’s .
In the beginning only single transmitter and single receiver is used for amplitude measurement .
Then after evolution occurred , just like openhole acoustic log , new design introduced , which measured signal amplitude near receiver .
Eventually borehole compensated device , using dual transmitter and dual receiver were introduced in 1980’s .
2. INTRODUCTION
• CBL was firstly design in 1960’s .
• In the beginning only single transmitter and single receiver is used for
amplitude measurement .
• Then after evolution occurred , just like openhole acoustic log , new design
introduced , which measured signal amplitude near receiver .
• Eventually borehole compensated device , using dual transmitter and dual
receiver were introduced in 1980’s .
3. Principle
• Basically , this log is used to measure amplitude in borehole .
• We used sonic waves to estimate amplitude and frequency in borehole.
• Sonic waves when passes through pores , amplitude and frequency both rise
while velocity become low in hard strata .
• While in smooth strata velocity become high , while amplitude and frequency
both become low .
4.
5. Devices
• In cement bond log , we used two types of devices .
• (1) Acoustic Sonic device (2) Ultra-Sonic device
• In acoustic device , acoustic signal is travel through borehole fluid , casing , cement ,
and the formation itself .
• The signal is received , processed , and displayed on a microseismogram .
• The recorded waves are presented together with the travel time and casing
amplitude curve , which display amplitude of acoustic signal , which travel through
casing.
6. • In ultra-sonic image tool in which transmitter emits sonic
waves of 200-700Hz frequency .
7.
8.
9. Uses
• To support the casing .
• To prevent fluid from leaking to surface .
• Isolating production zone from water bearing zone .
• CBLs clearly indicate top of cement, where there is unbonded pipe.
• CBLs also indicate where the pipe is well cemented .
10. Limitation
• CBLs are not reliable as indicators of hydraulic sealing by the cement ,
because they cannot detect small channels .
• Poor running and intercepting technique .
• CBLs transducer arrays are vertical , where bonding problem need to be
investigated circumferentially .
