环状刻槽钻铤中随钻方位电磁波响应的混合算法  

A hybrid algorithm for LWD azimuthal electromagnetic responses with annular grooved drill collar

作　　者：汪宏年[1] 于蕾[1] 王浩森 杨守文[1] 殷长春[3] WANG HongNian;YU Lei;WANG HaoSen;YANG ShouWen;YIN ChangChun(International Center for Computational Method and Software,College of Physics,Jilin University,Changchun 130012,China;Hebei Institute of Architecture and Civil Engineering,Zhangjiakou Hebei 075000,China;College of Geo-Exploration Sciences and Technology,Jilin University,Changchun 130026,China)

机构地区：[1]吉林大学计算方法与软件国际中心,长春130012 [2]河北建筑工程学院,河北张家口075000 [3]吉林大学地球探测科学与技术学院,长春130026

出　　处：《地球物理学报》2021年第5期1811-1829,共19页Chinese Journal of Geophysics

基　　金：中国科学院先导专项(XDA14020102);国家重点研发项目(2017YFC0601805);国家自然科学基金项目(41574110)联合资助.

摘　　要：为了提高随钻电磁波测井仪器的抗震能力,仪器传感器中所有发射与接收线圈均安装在柱状金属钻铤上的环状刻槽中,同时槽中充填高磁导率的铁氧体,以提高发射和接收效率.本文针对多环状刻槽钻铤中发射与接收线圈分布,研究建立一套随钻电磁响应的混合模拟算法.首先,根据环状刻槽几何尺寸以及轴向边界,将整个钻铤与外部的井眼和地层划分成多个不同电导率和磁导率分布的轴对称非均质各向同性层状模型,并应用混合法建立层状非均质地层中电磁场的半解析解与各个线圈上感应电动势的计算方法.其次,利用摄动原理给出随钻电磁测井中振幅比与相位差的空间灵敏度计算公式.然后,通过数值结果考察铁氧体磁导率和地层电导率变化对发射线圈的发射功率和接收线圈上感应电动势的影响,并确定各个接收线圈上感应电动势的动态变化范围,为仪器设计过程中选择合适的铁氧体提供理论依据.最后,通过空间灵敏度分布特征考察振幅比与相位差在探测特征上的差异.All the transmitting and receiving coils in the downhole sensors of LWD resistivity measurements are usually installed in the annular grooves on the metal drill collar for enhancement of anti-vibration capability of the instrument.The grooves are often filled with ferrite with high permeability in order to improve the transmitting and receiving efficiency.In this paper,a hybrid algorithm is applied to simulate the EM field excited by the transmitters on non-smooth metal mandrel for study and investigation of the tool responses.First of all,according to the spatial distribution and their axial interfaces of the annular grooves on the drill collar,we try to divide the entire metal drill collar,borehole and formation into several axisymmetric inhomogeneous layers with different radial distribution of both conductivity and relative magnetic permeability.Then a hybrid method is applied to solve the electromagnetic(EM)field excited by per transmitter and to obtain semi-analytical solution of the EM field in the layered inhomogeneous formation.On this basis,the spatial sensitivity of amplitude ratio and phase difference of LWD axial receiver coils are set up by using perturbation theory.Finally,we compute the induced electromotive forces on all coils including transmitters and receivers in formation with a series of formation conductivities and relative ferrite permeability to study and explore quantitatively the influence of the changes in both formation conductivity and relative ferrite permeability on the tool response,transmitter efficiency,and the dynamic range of inducing potential per receiver.That provides a theoretical basis for choice of proper ferrite during the process of instrument design.In addition,the detection characteristics of attenuation and phase shift is investigated through comparison of their spatial sensitivity.

关 键 词：随钻方位电磁波 混合法 环状刻槽 铁氧体 

分 类 号：P631[天文地球—地质矿产勘探]