井中低频声激发极化电场理论模型  

Theoretic model of low frequency ultrasonically induced polarization electric field in borehole.

作　　者：周成当[1] 杨体源 

机构地区：[1]石油勘探开发科学研究院 [2]青海石油管理局地质研究中心

出　　处：《石油地球物理勘探》2000年第2期193-201,共9页Oil Geophysical Prospecting

摘　　要：声激发极化是在声波作用下饱和流体孔隙介质中的声波场向电磁波场转化的一种非线性地球物理现象 ,即声能转化成电磁能的过程。在低频条件下 ,声源在井眼和地层中产生的波场能量主要以井眼斯通利波的形式存在并沿井眼壁传播 ,描述声激发极化过程的方程也可以得到相应的简化。本文首先模拟和分析了横向各向同性和均匀各向同性孔隙饱和介质在高频和低频下的全波列波形 ,然后在考虑到实际井眼中自然电场存在的前提条件下系统推导了低频声波激发极化电场的理论模型 。Ultrasonically induced polarization is a nonlinear geophysical phenomenon that acoustic field in fluid saturated porous medium changes into electromagnetic wave field while acoustic wave travels in the medium; in other words, it is also the process of acoustic energy changing into electromagnetic energy. Under low frequency condition, the wave field energies produced by acoustic source in both borehole and surrounding formation exist and travel along borehole wall mainly in the form of Stoneley wave, so that equation showing the process of ultrasonically induced polarization may be reduced relatively. The authors modeled and analysed full wavetrain waveforms in low and high frequency cases in transversally isotropic and homogeneous isotropic fluid saturated porous media. The theoretic model of low frequency ultrasonically induced polarization electric field is deduced systematically on the premise that there exists natural electric field in borehole. In addition, the concept and definition of sensitive coefficient of induced polarization is advanced also in the article.

关 键 词：理论模型 低频声激发极化 电场 超声波勘探 

分 类 号：P631.5[天文地球—地质矿产勘探]