瞬变电磁测井原理研究Ⅱ:精确解的响应  

Study on Transient Electromagnetic Logging Theory Ⅱ:The Response for Exact Solution

作　　者：臧德福 朱留方 沈永进[2] 沈建国[2] 

机构地区：[1]中石化胜利石油工程有限公司测井公司,山东东营257096 [2]天津大学电子信息工程学院功率超声实验室,天津300072

出　　处：《测井技术》2014年第3期267-272,共6页Well Logging Technology

摘　　要：Doll几何因子没有考虑地层的集肤效应和单元环之间的相互影响,所得到的响应在高电导率地层误差比较大。用Doll几何因子计算瞬变电磁测井响应的误差也相应比较大。用无限大均匀介质响应的精确解势函数计算瞬变电磁测井响应。与Doll几何因子不同,精确解势函数的实部和虚部都参与了计算,其响应的频谱总体变化趋势比较平稳,没有像Doll几何因子那样随频率线性增加,响应波形的实部与激发波形相似,虚部在激发波形突变处也呈脉冲形状。设计了含正负幅度值的方波激发波形,用这样的波形激发,其响应的实部与激发波形相近,虚部则在方波的突变处最大,随着时间的推移,幅度连续减小。进一步用势函数计算瞬变电磁感应电动势后发现,在激发波形的突变处,电磁感应电动势比较大,容易测量。As Doll geometric factor does not consider the skin effect of the stratum and neither the mutual influence of each unit loop,the error of response is relatively larger in high conductivity formation.Therefore,the error of transient electromagnetic logging response is relatively larger by using Doll geometric factor.In this paper,the transient electromagnetic logging response is calculated with the exact solution of potential function of homogeneous medium.Different with Doll geometric factor,the real and imaginary parts of the exact solution of potential function are involved in the calculation,the response spectrum of which is relatively stable,not like the Doll geometric factor that increases linearly with frequency.The real part of the response curve is similar with the excitation waveform,however,the imaginary part of which shows a pulse shape at the change of the excitation.The square wave excitation waveform with positive and negative amplitude value is designed,excited by such waveform,the real part response is similar with the excitation waveform,yet the imaginary part response is maximum at the change of the square wave.The amplitude decreases continuously over time.By further calculation of electromagnetic induction electromotive force with potential function,it is found that the electromagnetic induction electromotive force is the maximum and most easily to be measured when the excitation waveform changes from 0to negative value.

关 键 词：测井方法 瞬变激发 电磁感应 精确解 方波 

分 类 号：P631.84[天文地球—地质矿产勘探]