套管井体胶结状态对井孔中声传播的影响

从波动方程出发,利用匹配边界条件,木文推导出套管井中由单极子和多极子声源激发的井内声场定解表达式及相应的导波色散方程.利用实轴积分法和快速傅里叶交换数值方法,具体计算了套管井中不同胶结情况时由单极子声源和偶极子声源激发的井轴上不同源距处的全波列波形。结合套管井中的轴对称导波模式,分析了胶结状况对套管井中单极子和偶极子声源激发的声场的影响.研究结果表明:仅利用普通单极子声源或偶极子声源进行套管井测井,难以区分出套管胶结良好、套管与水泥为滑移胶结和自由套管情况三种不同的胶结情况;只有把普通单极子声源测井与偶极子声源测井结合起来,才有可能准确评价套管的胶结情况。

The effects of bonding conditions on the propagation of acoustic wave along a cased borehole

Based on the wave equations in cylindrically layered structures and boundary conditions, we have derived the frequency equation for axisymmetric guided waves and the expression for sound fields in a cased borehole excited by a monopole and multipole source. The synthetic full waveforms excited by the monopole and dipole source are simulated using a real axis integration and FFT method. According to the axisymmetric guided wave modes, we have analyzed the synthetic full waveforms and studied the effects of the interface conditions on the sound field in cased boreholes. Numerical results indicate that it may be difficult to distinguish well-bonded, poor bonded or unbonded intermediate layer between the metal tube and formation if only using a monopole source or dipole source. To precisely estimate the case boundary conditions, a combination of monopole source logging with dipole source logging is suggested.