关于充流体钻孔中的纵波和横波

虽然钻井中的声波传播理论已比较成熟，但在纵、横渡的激发机制方面仍存在着一些不同的观点。本文通过对纵、横波割线积分进行分析，导出了其远场近似解的表达式，并探讨了稳态情况下的共振和非共振纵、横波振幅的衰减问题，获得的主要结论如下：（1）共振纵、横波皆有几何扩散现象。其中，共振纵波的振幅按Z－1衰减；而共振横波的振幅则近似按衰减。（2）共振纵波的振幅与岩石、流体密度比P2／P1及纵、横波速度vP和vs有关；而共振横渡的幅度值除与上述几个因素有关外，还与共振频率、井半径α和流体速度vf有关。（3）非共振纵波的几何衰减介于z－1和［zln（z／α）］－1之间；而非共振横渡的几何衰减则介于z－2和之间。（4）在纵、横渡远场近似解中不存在奇点。

Compressional and shear waves in fluid-filled borehole

Although the propagation theory of acoustic wave in borehole is quite perfect,there are still some different opinions in the shot mechanisms of compressional andshear waves. Far field approximate solutions of compressional and shear waves areformulated by making analysis of secant line integrals of compressional and shearwaves. We analyse the amplitude attenuations of resonant and nonresonant com-pressional (shear) waves under stable condition. The analysis leads to the conclu-slons:. Resonant compressional and shear waves all show geometrical diffusionphenomena. The amplitude of resonant compressional waves attenuates in z-1,while the amplitude of resonant shear waves attenuates nearly in [ln(z/a). The amplitude of resonant compressional wave is related to both the ratio ofrock density to fluid density (P2/P1 ) and the velocities (VP and vs) of compressionaland shear waves;and the amplitude of resonant shear wave is related to not 0nly theabove factors but also resonant frequency ,borehole radius a and fluid velocityvf.. Geornetrical attenuation of nonresonant compressional wave ranges from z-1to; and the geometrical attenuation of nonresonant shear wave is be-tween z -2 and . No singular point exists in the far field approximate solutions of compres-sional and shear waves.