随钻方位电磁波仪器界面预测影响因素分析

Analysis on the Affecting Factors of Prediction Interface with Azimuthal LWD Electromagnetic Tool

随钻方位电磁波仪器的探测深度决定仪器的界面预测能力,了解随钻电磁波仪器在不同地层环境下的探测特性,对准确进行界面预测和判断有重要意义。模拟了仪器的界面响应特征以及边界走向与仪器工具面角的关系,介绍了随钻电磁波仪器探测深度的定义,通过模拟随钻方位电磁波电阻率的探测特性,分析了不同地层及仪器参数对随钻方位电磁波仪器探测深度以及界面距离反演结果的影响。结果表明,在地质导向过程中,相邻地层的电导率的差决定了随钻方位电磁波仪器的信号幅度,而相邻地层的电阻率对比度和电导率的差同时影响仪器的探测深度,同时仪器对交叉耦合分量电动势(Vzx)的分辨能力也决定了仪器的探测深度;界面距离反演地层模型中,低电阻率地层电阻率的精确度比高电阻率地层电阻率精确度对反演距离的正确性和准确度影响更大。

The detection depth of azimuthal LWD electromagnetic tool determines the ability of interface prediction. There is important significance to know the detecting characteristics of electromagnetic LWD tools under different formation conditions. The response characteristics of formation boundary and the relation between the boundary strike and tool＇s face are simulated, and the definition of detection depth of electromagnetic LWD tools is introduced. The influence of formation conditions and tools parameters on detection depth and inverted distance to bed is analyzed by simulating the response of azimuthal LWD electromagnetic tools. The simulation results show that the difference of adjacent formation conductivity determines the amplitude of geosteering signals, the ratio and the difference of adjacent formation resistivity jointly determines the depth of detection. The small signals resolution of cross-coupling component zx voltage also determines the detection depth of the LWD electromagnetic tool, the resistivity accuracy of low resistivity formation has greater effect on the inverted distance than that of the accuracy of high resistive formation in inversion models.