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THIS SINGLE MEASUREMENT (AMPLITUDE), AND THE OVERSIMPLIFIED <br />INTERPRETATION OF IT, IS FREQUENTLY THE SOURCE OF MUCH OF <br />THE CONTROVERSY AND ERROR REGARDING CEMENT BOND LOG <br />ANALYSIS. <br />To analyze a bond log, ignore the amplitude curve initially, go to the V DL and measure <br />the casing signal for free pipe. If the casing signal is not present, the signal must have <br />been attenuated. Then, go to the amplitude curve. Determine the time of the first arrivals <br />and their character. VDL formation signals should generally correlate with the gamma <br />log. The V DL is practically tamper-proof. The operator cannot change the property of <br />the rock, thus the time required for the signal to be transmitted. <br />Pitfalls in Bond Interpretation from Amplitude Response <br />A. Amplitude detection method -fixed gate or floating gate.. <br />B. Instrument centering.. <br />C. Insufficient curing time for cement. <br />D. Cement sheath less than 314 inch with either well centered or poorly <br />centered casing . <br />E. Micro annulus. <br />F. Gas bubbles in the borehole fluid. <br />G. Void spaces in the cement sheath. <br />H. Fast formation. <br />Cement bonded to the pipe. but not to the formation. <br />J. Changes in acoustic properties of the borehole fluid density and viscosity <br />die to pressure. temperature, and content. <br />K. Minimum amplitude signal in well bonded casing varies with respect to <br />casing size and casing weight. <br />L. Cements are mixed to pazticulaz specifications and maybe designed with <br />different compressive strengths. <br />M. Cement is sometimes gas cut. <br />4 <br />