井中偶极声源激励下的反射声场影响因素分析及仪器关键参数优选

根据远探测测井的实际背景,利用三维有限差分数值模拟方法精确考察井中偶极声源条件下声源激发频率、反射界面水平位置、地层界面倾角及偶极声源偏振方向对反射横波幅度的影响。结果表明:偶极横波远探测测井仪的最佳工作频率应选择在井孔挠曲波的截止频率以下,可解决来自地层深部的反射信号相对于沿井传播的直达波信号过于微弱的问题。按照现有的仪器范围设置(源距小于4m),可有效地探测地层倾角为40°～90°的井旁反射体。

Influencing factors analysis and remote acoustic sensing instrument preferences optimization on reflected shear-wave of fluid-filled borehole dipole excitation

According to practical needs of acoustic remote detection logging, the present paper investigates the influences of source frequency, reflection interface position, interface dip and dipole source orientation on S-wave reflection amplitude by using an accurate 3D finite difference numerical simulation method. Analysis results show that the operating frequency of the dipole S-wave remote detection instrument should be below the cut-off frequency of flexural wave, so as to enhance the amplitude of the reflected signal from formation reflector relative to that of the direct flexural wave along borehole. It is recommended that the data acquisition tool should have a source-to-receivers offset less than 4m in order to effectively image a formation reflector with a dip angle in 40°-90° range.