套管井声波测井中首波幅度衰减研究

讨论了套管波首波幅度关于源距衰减变化随着激发声源中心频率的变化而变化的关系.通过考察套管波首波幅度衰减快慢随声源中心频率变化规律,在理论上利用这些规律区分套管井第Ⅰ、Ⅱ界面均胶结良好和自由套管井2种情况,为实际固井质量定量解释提供一定的参考依据.对在不同声源中心频率作用下的套管首波的不同波峰幅值、不同波谷幅值和波峰-波谷峰峰值进行计算研究,为分析实际测井波形,以合适的幅度为更加准确地表征首波衰减提供了基础参数.认为当声源中心频率从低到高变化时,第Ⅰ、Ⅱ界面均胶结良好的套管井中首波幅度随源距的衰减系数的变化相差不大,但是在自由套管井中首波幅度随源距的衰减其系数有着明显的变化.

Study of Numerical Simulation on Amplitude Attenuation of First Arrivals in Cased-hole Acoustic Logging

Study on wave attenuation of first arrivals of acoustic logging in cased-hole might be helpful in quantitative cementation quality evaluation with acoustic logging.In cased-hole models with different cementation qualities,a series of acoustic logging waves are numerically simulated with real axis integral method,then several characteristic amplitude values(amplitude of first arrival,amplitudes of peaks,valleys and peak-valleys in front several vibrations of the first arrival) are fitted with source spacings by a exponential function to obtain so called "spacing attenuation factors" which quantitatively describe the attenuation process.Analysis results show that in well bonded cased-hole,the spacing attenuation factors are not close relative to varieties of center frequencies of the transmitter,nevertheless that are close related in free-pipe casing condition.