柱状双层声电效应测井界面电磁波  

Borehole interface converted electromagnetic wave of double cylindrical formation

作　　者：王伟豪 崔志文[1] Wang Wei-Hao;Cui Zhi-Wen(College of Physics, Jilin University, Changchun 130012, China)

机构地区：[1]吉林大学物理学院

出　　处：《物理学报》2019年第20期146-154,共9页Acta Physica Sinica

基　　金：吉林省科技发展计划(批准号:20180101282JC);国家自然科学基金(批准号:40974067)资助的课题~~

摘　　要：声波在含流体孔隙介质内传播的过程当中,会产生耦合电磁波,根据这一现象前人提出了声电效应测井的方法.本文探究了井外为柱状双层孔隙地层声电效应测井耦合声电场的产生机理和传播规律.通过计算电场支点的垂直割线积分,得到以地层电磁波速度传播的界面转换电磁波.对比不同夹层孔隙介质层厚的界面转换电磁波时域波形,可以发现每一次地层纵、横波传播至界面发生折反射时,都会产生界面转换电磁波,这些成分构成了界面转换电磁波的总响应.考察了孔隙介质流体矿化度对界面转换电磁波的影响,发现当介质分界面两侧孔隙介质流体矿化度差异越大时,界面转换电磁波的幅度越大,且两个界面所产生的电磁波互不影响.同时考察了仅存在矿化度界面的情况,发现声波传播至矿化度界面处也会产生界面转换电磁波,可以利用这一特性来探测井外介质电化学界面的位置.研究界面转换电磁波对于认识柱状双层孔隙地层声电效应测井的界面响应规律具有重要意义.In recent years, electrokinetic effect has received wide attention. The electrokinetic effect refers to the coupling and conversion of acoustic waves and electromagnetic waves in a porous medium. Due to the electric double layer structure of porous medium, electromagnetic waves are generated during acoustic waves propagation in the liquid-containing porous medium. Based on this phenomenon, one proposes a method for electrokinetic effect logging.The electrokinetic effect has great application prospects in earthquake prediction and engineering exploration. The generation mechanism and propagation law of acoustic-electric coupling wave in electrokinetic effect logging of double-cylindrical-layer porous medium are explored in this paper. By calculating the vertical secant integral of the electric field branch point, the total response of the interface converted electromagnetic wave can be obtained. Previously, in the cylindrical layered medium, the secant integral corresponding to the borehole fluid and the inner layer medium branch point is zero. So the examples in this paper are calculated from the vertical secant integral of branch point kem2, which corresponds to the outermost infinite medium. It is found that when each time the longitudinal and transverse waves of the formation propagate to the interface, the interface converted electromagnetic waves are generated. These converted electromagnetic waves constitute the total response of the interface converted electromagnetic wave.At the same time, the influence of porous medium fluid salinity on interface converted electromagnetic wave is investigated. It is found that when only the inner layer porous medium fluid salinity changes, the amplitude of the interface converted electromagnetic wave response of the two interfaces is affected. When only the salinity of the outermost porous medium fluid changes, only the amplitude of the interface converted electromagnetic wave generated at the second interface is affected, but the interface electromagnetic waves generate

关 键 词：声电效应 孔隙地层 割线积分 界面转换电磁波 

分 类 号：TE151[石油与天然气工程—油气勘探]