Numerical Simulation Of Segmented Bond Tool And The Investigation On Attenuation Of The Casing Wave

AbstractSegmented bond Tool(SBT) is an excellent technology applied to Primary Cement Evaluation, and it has recently been servicing in Field Producing. It has many advantages over conventional ones such as CBL and VDL. However, logging company at home has to buy the tool and its relevant software with lots of money, as a result the logging cost is very high and this tool cannot be widely used. The working Principle of SBT in Cased Hole under Different Bonded Conditions is studied through numerical modeling by combining experiment measurement in the paper to provide some useful advice for those engineers who develop the tool.In view of the casing well structure,establish a theory calculation model for multilayered medium in the round tube and the thin plank,and calculate the phase velocity dispersion curves and the attenuation curves about the Lamb wave(the extension wave and the flexural wave)generated in the round tube and the thin plank. The result is that the phase velocity dispersion curves and the attenuation curves generated in the thin plank under SBT logging spectrum(60k Hz~100k Hz)is in basic agreement on that in the round tube which establishes a theoretical basis of the stud y about the Lamb wave generated in SBT by calculating a easier model for multilayered medium in the thin plank. Then, further study the phase velocity dispersion feature and attenuation feature of Lamb wave generated in different casing thickness,different cement density and different acoustic impedance. And gain the rule about casing wave attenuation changing with casing dimension and cement density. The full waveforms generated by SBT in Cased Hole under Different Bonded Conditions are numerically investigated by the method of the real axis integration and finitude difference. Discuss the influence attached the skateboard is to the recorded waveform and find that the results of numerical simulation and experimental results are in good agreement.Lamb wave generated by SBT is dispersion wave, the attenuation value gained by ratio calculating the peak of the waveform directly is bigger than theoretical value because of the influence of dispersion. The result is that the compensating acoustic attenuation can not reflect the real stratum acoustic attenuation. This study eliminate the attenuation caused by Lamb wave dispersion with dispersion correction, and to some extent gain the attenuation coefficient directly related to the bonded conditions.