微电阻率成像仪数值模拟与分析

目前，很多油气田已经进入开发后期，勘探开发中常常遇到复杂的地层结构等问题，需要高分辨率的探测仪器，而阵列测井仪器在此方面得到了很好的应用。文章研究了用于复杂地层成像的微电阻率成像仪，在给出了成像仪电极系结构、电阻率测量原理之后，针对该仪器的复杂激励条件和复杂边界条件，采用三维有限元方法，利用双共轭梯度方法求解矩阵方程，进行非均匀介质中微电阻率成像仪的数值模拟。在成像仪所有的结构参数中，几何尺寸发生改变后，有可能影响测量结果的仪器参数包括金属芯棒的长度、绝缘棒的长度、回路电极的长度、极板的长度和宽度。相对而言，金属芯棒、绝缘棒和回路电极的长度对探测深度的影响较小，而极板的长度和宽度影响较大。最后，就这两个仪器结构参数对仪器探测深度的影响等问题进行了分析，并给出了不同几何尺寸条件下成像仪的探测深度结果。

NUMERICAL SIMULATION AND ANALYSIS OF MICRORESISTIVITY IMAGING TOOL

High resolution well logging tools are needed to solve various problems such as complex formation structure occurring in the process of exploration and production in mature oilfields. Array logging tools have been successfully applied to solve these problems. Microresistivity imaging tool for complex strata is presented in this paper. Its electrode configuration and principle of resistivity measurement are introduced. In view of the complex excitation and boundary conditions, numerical simulation of microresistivity imaging tool in heterogeneous medium is performed by using 3D finite element method and solving matrix equation with double conjugate gradient method. After the geometry of the imaging tool changes, parameters that may influence measurement results include the lengths of metal mandrel, insulated rod and return circuit electrode, as well as the length and width of plate electrode. In comparison, the influences of the lengths of metal mandrel, insulated rod and return circuit electrode on depth of investigation are relatively small, while that of the length and width of plate electrode are relatively large. The later is discussed in detail and the depths of investigation at different geometries are presented.