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声波测井过程中获取的速度到底是相速度还是群速度,目前仍存在一些争议,本文从理论分析和数值模拟的角度,使用三种模型对这一问题进行了研究。首先,构造一个相速度与群速度可调的稳态声波传播模型——不同声速的两个平面波叠加模型,利用慢度时间相关(STC)方法提取声波波速,数值模拟结果表明,无论相速度较大或是群速度较大,STC方法提取出来的波速都是相速度;其次,通过频散分析和割线积分得到刚性壁圆柱流体模型中的频散曲线与分波波形,使用STC方法得到的速度与相速度的频散曲线吻合较好,而直接读取波至获得的速度与群速度的频散曲线趋势一致;最后,利用频散分析和实轴积分方法,获得偶极子在慢地层中激发的模式及全波波形,得到的结果再次验证了刚性壁圆柱流体模型中的结论。
There are still some controversies about whether the speed obtained during sonic logging is phase velocity or group velocity. In this paper, three kinds of models are used to study this problem from theoretical analysis and numerical simulation. First of all, a steady-state sound wave propagation model with adjustable phase velocity and group velocity - two plane wave superposition models with different sound velocities is constructed, and the acoustic velocity is extracted by the slow time correlation (STC) method. The numerical simulation results show that, regardless of the phase velocity Large or large group velocity, and the wave velocity extracted by the STC method is the phase velocity. Secondly, the dispersion curve and the wave form in the rigid-wall cylindrical fluid model are obtained by the dispersion analysis and the secant integral. Using the STC method, The velocity and phase velocity of the dispersion curve are in good agreement, while the direct reading wave to obtain the velocity and group velocity dispersion curve trend; Finally, the use of dispersion analysis and real axis integration method to obtain the dipole in the slow formation And the full-wave waveform. The obtained results verify the conclusion in the rigid-wall cylindrical fluid model.