多频电磁波测井的数值模拟和实验研究  

Numerical and Experimental Study on Multi-frequency Electromagnetic Well Logging.

作　　者：刘四新[1] 佐藤源之[2] 

机构地区：[1]吉林大学地球物理系 [2]日本国东北大学东北亚研究中心

出　　处：《测井技术》2003年第4期278-282,共5页Well Logging Technology

基　　金：吉林大学青年基金资助(2002年);教育部回国人员启动基金资助(2002年)

摘　　要：介绍了一种新开发的用于实验目的的多频电磁波测井系统。该系统井下探头为单发双收型,数据采用光纤进行传输,天线采用具有一定带宽的柱型偶极子天线,地面采用计算机控制的网络分析仪进行测量。天线的频率范围大约在40～100 MHz。测得的幅度比和相位差用转换图版转换成直接反映地层物理性质的电导率和介电常数。介电常数主要取决于信号的相位差,而电导率主要取决于信号的幅度比。介电常数的灵敏度范围比较宽,而电导率小于0.001 S/m时电导率的测量变得不敏感。用时间域有限差分法(FDTD)给出各种情况下油水界面时的多频电磁波测井响应,计算结果表明,即使在地层水不导电的情况下,介电常数也可用来区分含油层和含水层。给出该系统在试验井中的实测结果,并和井下电视的图像取得较好的对应。A novel experimental multi-frequency electromagnetic well logging system is introduced. The downhole sonde includes one transmitter and two receivers, while the data is transmitted through optical fibers. The antenna employed is cylindrical dipole with certain frequency width, the surface unit includes a network analyzer controlled by computer. The frequency range of the antenna is about 40-100 MHz. The measured amplitude ratio and phase difference are converted into the conductivity and the dielectric constant which are related to the physical property of the surrounding formation. The dielectric constant is mainly determined by the phase difference while the conductivity is mainly determined by the amplitude ratio. The sensitivity of the dielectric constant is higher but the conductivity measurement is not so sensitive while the conductivity is less than 0. 001 S/m. The Finite Difference Time Domain (FDTD)method is applied to compute the responses of the multi-frequency electromagnetic well logging. It is demonstrated that dielectric constant can be used to discern the water layer and the oil layer in petroleum industry even if the formation water is not saline. The developed system is testified experimentally in a test borehole, the measured results from which are in good agreement with the borehole television image.

关 键 词：多频电磁波测井 数值模拟 实验研究 介电常数 电导率 时间域有限差分法 油水界面 测量原理 

分 类 号：P631.811[天文地球—地质矿产勘探]