摘要
现有的随钻声波测井通常采用三种测量方式:单极子、偶极子及四极子测量模式.分别采用单极子源、偶极子源和四极子源激发单极子、偶极子和四极子信号对地层速度信息进行测量.由于随钻测井环境比较复杂,钻杆在井孔中占据大部分空间,钻杆速度高于地层速度,导致接收到的信号中仪器波能量占主导,无法有效地提取地层的纵横波速度信息.本文探讨一种采用非对称偏心的点声源,一次激发,利用方位分布的四个接收器接收,经过合成后同时分别得到单极子、偶极子和四极子模式波信号的测量方法,为建立同时利用多极模式波信号测量地层纵横波速度的随钻声波测井实用技术提供基础.本文利用1∶12的缩比模型在实验室对该方法进行了考察,实验结果证明,可以通过非对称点声源得到有效的地层单极子、偶极子和四极子模式波信号.通过分析和对比实测数据和理论模拟的频散曲线,本文进一步提出利用三种模式波的频散曲线联合反演确定地层横波速度的方法.
Currently, acoustic logging while drilling （LWD） mainly generates and employs three measurement modes separately by excitation of a pure monopole, dipole or quadrupole source correspondingly. Due to the complication of the LWD operating environment, we often can not get expected signal by traditional single mode measurement. We propose in this paper an approach to trigger all the modes simultaneously in the borehole using an asymmetric point source. Four receivers are azimuthally distributed around the LWD tool to receive the signals of all modes propagating in the borehole. By combining the signals from the four receivers in different ways we can get monopole, dipole and quadrupole waveforms in every single measurement. In this way, we can evaluate formation velocities using multiple modes simultaneously. We tested this method with a scaled borehole and LWD tool model of 1 ： 12 in laboratory. And the lab results confirm that we can get effective monopole, dipole and quadrupole signals by an asymmetric source and measure these modes simultaneously. Finally, based on the theoretical analysis of the lab data in time and frequency domain, we demonstrated that the formation shear velocity can be determined by a joint inversion of the monopole, dipole and quadrupole dispersion curves.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2012年第1期327-332,共6页
Chinese Journal of Geophysics
基金
国家科技重大专项大型油气田及煤层气开发课题20(2008ZX 05000-020)
国家重点基础研究计划项目973(2007CB209601)
中国石油大学(北京)科研项目(YJRC-2011-12)资助
关键词
随钻声波测井
缩比模型
非对称偏心声源
Acoustic logging while drilling, Scaled model, Asymmetric source
