摘要
Based on the wave equations in cylindrically layered structures and boundary conditions, the frequency equation for axisymmetric guided waves and the expression for sound fields in a cased borehole excited by a monopole or multipole source have been derived. 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, the synthetic full waveforms and the effects of the interface conditions on the sound field in a cased borehole have been analyzed and studied respectively. Numerical results indicate that it may be difficult to distinguish well bonded, poorly bonded or unbonded intermediate layer between the steel pipe and formation if only using a monopole source or dipole source. To properly estimate the case boundary conditions, a combination of monopole source logging with dipole source logging is suggested.
Based on the wave equations in cylindrically layered structures and boundary conditions, the frequency equation for axisymmetric guided waves and the expression for sound fields in a cased borehole excited by a monopole or multipole source have been derived. 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, the synthetic full waveforms and the effects of the interface conditions on the sound field in a cased borehole have been analyzed and studied respectively. Numerical results indicate that it may be difficult to distinguish well bonded, poorly bonded or unbonded intermediate layer between the steel pipe and formation if only using a monopole source or dipole source. To properly estimate the case boundary conditions, a combination of monopole source logging with dipole source logging is suggested.
基金
The project is supported by the National Natural Science Foundation of China and Natural ScienceFoundation of Jiangsu Province
