随钻电磁波测井井眼响应特性分析

Analysis of response of LWD's electromagnetic wave propagation tool in horizontal wells with the FDTD method.

文章介绍了水平井随钻电磁波测井响应的时域有限差分FDTD数值计算方法。首先根据水平井测井地层的特点,利用直角坐标系下的三维FDTD计算公式、稳定性条件和吸收边界条件,设计实现数值计算程序;然后分析随钻电磁波测井仪在水平井中的几种状态时磁场的响应特性,这些状态有仪器居中、偏心和不同泥浆电导率。结果表明,偏心和井眼对测量信号的影响主要体现在相位曲线上,偏心和井眼校正主要通过制作相位图板来进行校正。开发的数值模拟计算软件可用于随钻电磁波测井仪器设计。

This thesis studies the finite difference time domain(FDTD)method which is used to compute LWD electromagnetic wave logging response in the horizontal well.Firstly,three dimensional FDTD formulas in the Cartesian coordinate system,its stable and absorbing boundary conditions(ABC)are used and the numerical calculation code is designed.Finally,the response characteristics of magnetic field of LWD tool is analyzed in several tool states in horizontal well.These states include tool center,tool eccentricity,and different mud conductivity condition in borehole. The results show that the changes of magnetic field response appear mainly in the phase curves and a little in the amplitude curves.Eccentric correction and borehole correction can be settled from the phase change chart.The developed numerical modeling software can be applied to design the new LWD tool.