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J - <br />Circumjerentia! Acoustic Scanning Tool (CAST) impedance values for Fluids are very consistent and manifests itself as a fairly straight line on the log. Cement slurries, <br />are more variable and show up as curves with much more activity or variability. By analyzing the value and the character of [he vnpedance curves, it is possible [o <br />successfully evaluate the cement quality ofconventional and lightweight cements. Typical impedance values for common materials or fluids are: <br />Gas or au < .5 high activity curve response <br />Water I.5 flat consistent curve response <br />Drilling Mud I.5 - 2.5 flat consistent curve response <br />Lightweight Cements <1 - 4 high activity curve response <br />Conventional Cements 2 - 6 medium to high activity curve response depending consistency of slurry <br />Cement Bond Log (CBL) tools evaluate cement bonding to pipe and formation by measuring the changes in sound waves traveling through casing, cement, <br />and formation. Log presentations include a pipe amplitude curve and aMicro-Seismogram ®display in the form of light to dark shades. The amplitude <br />curve in lightweight cements will not read as low as published values for com-entional cements. Comparisons to lowest value and to free pipe value are <br />necessary to fully evaluate. Pipe signal will not completely disappear in lightweight cement as in conventional cements. <br />Respectfully, <br />Tom Riebel <br />Halliburton Energy Services <br />