非均质各向异性地层中方位随钻电磁测井响应三维有限体积法数值模拟算法

发布时间：2018-09-05 09:41

【摘要】：方位随钻电磁测井是一种能够实时探测地层边界、实现地质导向与井眼成像的新型测井技术.本文根据方位随钻电磁测井仪器的典型线圈系结构,首先引入柱坐标系下非均质完全各向异性地层中电流源并矢Green函数,并利用电磁场叠加原理给出倾斜发射线圈激发的电场以及倾斜接收线圈上感应电动势的计算公式;然后应用电流源电场并矢Green函数的混合势克服非均质地层中电磁数值模拟的低感应数问题,通过ρ和z方向上Lebedev网格设法降低网格节点个数,并且利用标准化算法确定柱坐标系下非均质单元上的等效电导率.在此基础上,用三维有限体积法建立柱坐标系电场混合势的离散方法,得到一个交错网格上电场矢势和标势大型代数方程,并用不完全LU分解以及稳定双共轭梯度法确定数值解.最后,通过数据模拟结果对算法的有效性进行检验,并考察钻铤、线圈倾斜角度以及地层各向异性等参数对仪器响应的影响.数值结果表明:在柱坐标系下用三维有限体积法的数值模拟算法处理非均质各向异性层中方位随钻电磁测井响应可以得到很好的结果.钻铤、电导率各向异性、层边界均对方位随钻电磁波测井响应产生较大的影响;在电阻率较大的地层,幅度比和相位差响应越小;发射线圈和接收线圈同时倾斜时,幅度比和相位差响应受地层的影响更灵敏.
[Abstract]:Azimuth while drilling electromagnetic logging is a new logging technology which can detect formation boundary in real time and realize geological guidance and borehole imaging. According to the typical coil system structure of azimuth while drilling electromagnetic logging tool, this paper first introduces the dyadic Green function of current source in heterogeneous completely anisotropic formation in cylindrical coordinate system. Based on the superposition principle of electromagnetic field, the formulas of the electric field excited by the inclined transmitting coil and the induction electromotive force on the inclined receiving coil are given. Then, the low induction number problem of electromagnetic numerical simulation in heterogeneous strata is overcome by using the mixed potential of dyadic Green function of current source electric field, and the number of mesh nodes is reduced by using Lebedev mesh in 蟻 and z directions. The equivalent conductivity of heterogeneous elements in cylindrical coordinate system is determined by standardized algorithm. On this basis, the discrete method of electric field mixing potential in cylindrical coordinate system is established by using three-dimensional finite volume method, and a large algebraic equation of electric field vector potential and scalar potential on staggered grid is obtained. The numerical solution is determined by incomplete LU decomposition and stable double conjugate gradient method. Finally, the validity of the algorithm is tested by the data simulation results, and the effects of drill collar, coil tilt angle and formation anisotropy on the instrument response are investigated. The numerical results show that the numerical simulation of azimuth while drilling in anisotropic layers can obtain good results in cylindrical coordinate system. In drill collars, anisotropy of conductivity and boundary of layer have great influence on the response of electromagnetic wave logging with drilling azimuth. The smaller the amplitude ratio and phase difference response are, the smaller the amplitude ratio and phase difference response are, when the transmitting coil and receiving coil are inclined at the same time, The amplitude ratio and the phase difference response are more sensitive to the formation.
【作者单位】：吉林大学物理学院;中国石油集团测井有限公司;
【基金】：国家自然科学基金(批准号:41574110) 国家科技重大专项(批准号:2011ZX0520-001)资助的课题~~
【分类号】：P631.811

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