基于软地层随钻多极子声源传播特性的数值研究

基于软地层测量横波的难题,数值考察了软地层随钻测井多极子波的频散特性及声全波波形,对比分析了电缆和随钻多极子声波测井.研究结果表明,随钻测井环境下,单极和偶极声源激发幅度很强的钻铤模式波严重干扰地层纵波或横波的测量;而四极子声源低频时只激发地层模式的四极子波,且截止频率附近以地层横波速度传播.因此,四极子声源最适合于随钻测井的地层横波速度测量.

On Numerical Study of the LWD Multipole Source Propagation Characteristics in Slow Formation

Since it is difficult to measure the shear wave in slow formation,we numerically investigate the dispersion and full waveforms of Logging-While-Drilling(LWD) multipole wave in slow formation,and compare the wireline logging with the LWD multipole acoustic logging.The compared results show that in the LWD environment,monopole and dipole sources can activate collor mode wave which has very large amplitude,and thus seriously disturbs the measurements of formation compressional or shear wave;while when the quadrupole source is at low frequency,it can only explode formation mode quadrupole wave,which propagates at the shear velocity in the cut off frequency.Therefore,in LWD,the quadrupole source is suitable to measuring the formation shear velocity.