含环状天线槽正交方位随钻电磁波测井仪器三维有限体积法数值模拟  

Numerical simulation of the LWD orthogonal azimuth electromagnetic tool with annular antenna recesses by the 3D finite volume method

作　　者：于蕾 王浩森 汪宏年[1] 杨守文[1] 殷长春[3] YU Lei;WANG HaoSen;WANG HongNian;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]吉林大学物理学院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9期3391-3409,共19页Chinese Journal of Geophysics

基　　金：中国科学院先导专项A(XDA14020102);国家重点研发项目(2017YFC0601805,2018YFF01013304);自然科学基金项目(41574110)联合资助.

摘　　要：针对由多环状天线槽构成的方位随钻电磁波测井仪器真实结构,基于柱坐标系下耦合势Helmholtz方程和三维有限体积法研究建立一套相应的三维电磁响应数值模拟算法.首先,采用柱坐标系下三维不规则Yee氏交错网格对计算区域进行剖分,保证了钻铤表面附近的剖分网格与非光滑刻槽钻铤表面同形;并利用电场延拓边界条件逼近钻铤表面的理想电导体边界条件,保证非光滑刻槽钻铤表面耦合势方程离散精度.在此基础上,应用标准均质化技术确定非均质网格的等效电导率和磁导率,并借助三维有限体积法对柱坐标系中耦合势方程以及环状天线槽内的发射天线进行离散,得到一个大型非对称稀疏代数方程,通过PARDISO直接求解器求解离散方程.最后,通过与柱状均匀地层中模式匹配算法所得的数值结果的对比验证该三维算法的有效性,并进一步通过数值结果研究考察金属钻铤和天线槽对方位随钻电磁响应的影响,以及层状TI地层模型中该仪器的响应特征.All antennas of the sensor of the LWD orthogonal azimuth electromagnetic tool(LWD-OAEMT)are installed in the annular recesses on the grooved metal drill collar.The recesses are often filled with ferrite or other magnetic materials to seal the coils.In this paper,we apply the Helmholtz equations about coupling potentials and three-dimensional finite volume method(3D FVM)with cylindrical grids to simulate the responses of the LWD tool consisting of multiple antenna recesses on the non-smooth grooved metal mandrel surface.Firstly,irregular Yee′s staggered grids in cylindrical-coordinate system are used to guarantee the grid near the mandrel surface is conformal with the non-smooth grooved tool geometry.The electrical field continuation technique is employed to approximate the perfectly electric conductor(PEC)boundary condition in order to efficiently improve the discretization precision of the coupling potential on the grooved drill collar surface.On this basis,the equivalent conductivity and magnetic permeability in a heterogeneous element are determined by the standardization technique,and the 3D FVM is employed to discretize the coupling potential equations in the cylindrical coordinates and the transmitting antennas in the annular recesses.Then,the Parallel Direct Sparse Solver(PARDISO)is used to solve the discrete equations to ensure the accuracy of numerical simulation and increase the stability of solutions.Finally,the 3D FVM is validated with comparison of results by numerical model matching(NMM)algorithm in homogeneous formation.In terms of numerical results,we further examine the influence of metal drill collar and antenna recesses on the LWD tool and its response characteristics in the layered TI formation model with different borehole dipping angles.

关 键 词：方位随钻电磁波测井 刻槽钻铤 铁氧体材料 环状天线槽 三维有限体积法 电场延拓边界条件 

分 类 号：P631[天文地球—地质矿产勘探]