套管井声波全波列中地层波的幅度特性

套管井声全渡中的地层波可以检测固井第二界面的水泥胶结质量状况.地层波不仅受地层衰减、套管波干扰等因素影响,更主要受第二界面两侧的声阻抗差值的影响.为此,基于固体介质的声势函数和界面的边界条件,推导了固-固界面纵横波的反射系数和透射系数,以及第一临界角入射情况下反射系数和透射系数的近似公式,并且分析了透射系数与声阻抗之间的关系.数值计算结果发现,地层波幅度随第二界面两侧声阻抗差增大而减小,且这种关系是非线性的.基于临界入射的透射系数,对经过衰减校正和干扰校正的地层波进行声阻抗校正,消除地层声阻抗对地层波幅度影响.使用地层波幅度评价第二界面的水泥胶结状况,并在实际资料处理中见到了好的效果.

Amplitude features of formation wave in acoustic full waveform of casing wells

We utilize formation wave of acoustic full waveform in casing wells to detect cementing quality of the secondary interface. Except for formation attenuation and casing wave disturb, the formation wave is mainly influenced by acoustic impedance gradient of the secondary interface. Hence, based on acoustic potential function and boundary condition on solid interface, we get reflection coefficient and refraction coefficient of longitudinal wave and transverse wave on solid-solid interface, and provide approximate formula of the reflection coefficient and the refraction coefficient about the first critical angle of incidence. We analyze relation between the refraction coefficient and acoustic impedance. Numerical results show that the amplitude value of the formation wave reduces with increasing acoustic impedance gradients of the secondary interface. The relation is nonlinear. After attenuation correcting and disturb correcting, we reprocess the formation wave by acoustic impedance correcting based on refraction coefficient of critical incidence in order to eliminate formation acoustic impedance factor of influencing the formation wave. In field data processing, we utilize the formation wave amplitude to estimate cementing quality of the secondary interface, and gain good results.