对称化测量高频电磁波测井的理论研究

THE THEORETICAL RESEARCH OF HIGH FREQUENCY ELECTROMAGNETIC WAVE LOGGING BY SYMMETRICAL MEASUREMENT

应用半解析数值模式匹配法研究了在含有任意数目的水平与柱状分层介质中的电磁波测井响应．通过数值模拟，发现现有的单发双收高频电磁波测井仪器由于其收、发结构不对称，往往会导致幅度比测井曲线的严重失真，使得它与相位差测井曲线很不匹配，大大降低了仪器的分辨能力；并指出了现有仪器的这种缺陷可以采用对称化测量来克服．本文首次系统考察了对称化测量高频电磁波测井的侵入和围岩影响，发现围岩影响可使相位差测量出现负响应，而侵入影响可使幅度比出现负响应，侵入和围岩影响之间存在一定程度的抵消作用，这对识别薄储集层是有利的．

In this paper an efficient numerical mode matching method is used to analyze the electromagnetic response for the high frequency electromagnetic wave logging. The borehole environment consists of an arbitrary number of horizontal and cylldrlcal layers. By numerical modeling, it is found that the asymmetric measurement of present T1-R1-R2 (one transmitter and two receivers) tool, because of its asymmetric form, often results in great distortion of the amplitude-ratio curve and no matching between the curves of amplitude-ratio and phase difference. This lowers the tool resolution. These drawbacks can be overcomed by symmetrical measurement. The effects of invasion and enclosing rock of high frequency electromagnetic wave logging with symmetrical measurement are first investigated systematilly. An interesting feature is the negative response seen in phase difference measurement by the shoulder effect and in amplitude ratio by me invasive effect. It is found that there is some compensation between me effects of invasion and enclosing rock. This is advantageous to discerning thin reservoir bed.