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this and that proper correlation is taken into account prior to perforating. <br />Instrument Centerine <br />A. If the logging instrument is properly centered in free or poorly bonded <br />pipe, the travel time should be a reasonably precise value. <br />B. Travel time measurement is the time it takes the signal to leave the <br />transmitter and return to the receiver. This is not formation bonding. <br />There is no way to tell fonnation bonding quantitatively. Travel time can <br />be very useful It can be used to determine whether or not the tool is <br />centralized. Travel time will occur eazly if an instrument is poorly <br />centered. <br />C. Amplitude can also increase when casing is eccentered because a portion <br />of the annulaz cement sheath is either absent or extremely thin. (less than <br />3/4 inch). <br />Cycle Skippine <br />Cycle skipping to later amplitude arrivals is caused by the attenuation of pipe <br />arrivals. <br />Stretch <br />A. Travel-time stretch may occur when an attenuated first pipe arrival is <br />detected in bonded intervals. <br />B. Stretch is often an indication of adequate zone isolation. <br />Casing Collars <br />A. Casing collazs are identified as a decrease in the amplitude, a slight <br />increase in TT, and/or cleaz chevron ("W") patterns on the VDL.. <br />B. The distance between the "W" pattern corners on the V DL represents the <br />transmitter-receiver spacing. <br />C. Casing collaz anomalies are typically not appazent in well bonded casing. <br />D. Caliper information defining the size and perhaps the shape and rugosity <br />of the borehole wall behind pipe is always an important criteria to log <br />analysis of cement condition. <br />6 <br />