随钻电阻率地层边界响应特征分析及应用

针对大斜度井、水平井随钻电阻率测井过程中随钻电阻率受地层界面影响大、极化效应明显的问题，从电磁场基本理论出发，建立了层状地层模型，利用数值模拟方法模拟了随钻电阻率测井仪以水平姿态穿过不同电阻率地层界面时的响应特征，分析了地层界面附近随钻电阻率测井仪的响应规律，总结了极化效应的产生前提和影响因素。结果表明，随钻电阻率测井仪的线圈距越大、工作频率越高，极化效应越显著，相位差电阻率与幅度比电阻率相比受极化效应的影响更明显。以永X断块A井为例，介绍了随钻电阻率地层边界响应特征在地质导向钻井中的应用情况。研究结果表明，在地质模型较为确定的情况下，可以利用随钻电阻率曲线的极化现象判断地层界面，进行地质导向。 

The Analysis and Application of Formation Interface Response Characteristics of the Resistivity LWD Tool

During resistivity logging while drilling (resistivity LWD) in highly deviated or horizontal wells, the resistivity is significantly affected by the formation interface and dramatic polarization effects can occur. According to the fundamental theory of electromagnetic fields, a model for layered formations was established, and numerical simulations were used to simulate the response when the resistivity LWD tool was horizontally penetrating the interface among formations with different resistivity. In this way, the response patterns of the resistivity LWD tool were analyzed and the preconditions and influencing factors of polarization effects were summarized. The results show that more significant polarization effect will be shown under larger coil spacing and higher working frequency of the tool. Comparing the amplitude difference resistivity, phase difference resistivity is more susceptible to polarization effects. Taking Well A in Yong-X Fault Block as an example, the applications of formation interface response characteristics from resistivity LWD tool were presented. It was indicated that polarization effects of resistivity LWD logs can be used to identify formation interfaces at given specific geological models to facilitate geosteering.