补偿型随钻电磁波电阻率测井仪的仿真研究

Numerical Simulation of Borehole Compensated Electromagnetic Wave Resistivity Tool in LWD Environments

井眼补偿误差严重影响随钻测井的精度,普通的随钻电磁波电阻率测井仪由于自身结构特点而不能提供误差校正,因此研究补偿型仪器具有重要意义。在井眼补偿问题的研究中,考虑到研究对象的几何形状特征以及运算结果的精度要求,首次采用了圆柱坐标系时域有限差分方法对非均匀地层情况下等源距补偿仪器和不等源距补偿仪器进行数值建模分析,仿真后得到两种仪器的响应及补偿曲线。重点分析了地层的非均匀性对井眼补偿误差及两种补偿仪器补偿曲线的影响,对地层分析以及测井资料的解释提供了重要的理论指导意义。

Because of the characteristics of the tools, borehole errors have great influence on the responses of traditional electromagnetic tools and reduce the accuracy of the measurement. It is necessary to compensate the logging data, and there are two kinds of compensated instruments available： iso-spacing compensated instruments and aniso-spacing compensated instruments. Numerical simulation can serve as an efficient method to investigate the performances of these approaches. The responses of two kinds of compensated tools in a three -layer formation were simulated using Finite Difference Time Domain （FDTD） Method. The FDTD method was implemented in three-dimensional （3-D） cylindrical coordinates for higher accuracy. It was analyzed how the heterogeneous formations influenced the borehole errors and the responses of the two kinds of compensated tools. This work can provide a reference value to evaluate formation and interpret logging data.