摘要
偶极横波远探测技术作为近年来发展起来的一门地球物理测井技术,一个重要应用前景就是在裸眼井和套管井测井时寻找井外地层中的油气构造.本文从井中偶极声场积分表达式的远场渐近解出发,对裸眼井及套管井中偶极声源的辐射场进行了对比分析,首次得到了偶极声源在不同声源频率和不同地层类型下的辐射特征.并深入研究了套管井中偶极声源的SH横波远场辐射特性,给出了不同耦合情况下的SH横波远场辐射特性的变化规律,对比了套前套后SH横波远场辐射的异同.结果表明:井中偶极声源的远场辐射特性受声源频率和地层类型影响较大;在套管井中,偶极声源辐射到地层中的横波能量也可以进行远探测,尽管与裸眼井情况相比,辐射能量会有所降低.本文的结果为偶极横波远探测技术的应用提供了理论支持.
Single-well shear-wave imaging using borehole dipole source has recently emerged as an important geophysical well-logging technology to detect formation geologic structures outside an open or cased borehole. Using an integral formulation of the elastic wave-field and solving it using an asymptotic solution, we analyze and compare the radiation of a borehole dipole source in open and cased boreholes. We report, for the first time, the dipole radiation characteristics in fast and slow formations for the frequency range used in the single-well shear-wave imaging. In particular, we analyze the radiation characteristics of SH waves from a cased borehole for the bonded and no-bonding conditions and compare the results with those for the open-hole condition. Our results demonstrate that the dipole radiation characteristics are significantly influenced by formation elastic parameters and source frequency. For a cased borehole, the casing reduces the shear-wave radiation to some extent. However, the radiated wave energy is still significant to allow for applying dipole-shear wave imaging in cased boreholes. Our analysis results provide a theoretical support for the application of the dipole shear-wave imaging technology.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2014年第5期1683-1692,共10页
Chinese Journal of Geophysics
基金
国家重点基础研究发展计划(2014CB239006)资助
关键词
井外声场
偶极声源
远场辐射
声波远探测
套管井
Borehole source radiation
Dipole souree
Far-field radiation
Single-well shear-wave imaging
Cased hole
