瞬变电磁波测井边界远探测方法研究  

Detection of the remote boundary using the transient electromagnetic logging method

作　　者：袁习勇 邓少贵[1,2,3] 胡旭飞 张盼 刘天淋 蔡联云 李海涛 YUAN XiYong;DENG ShaoGui;HU XuFei;ZHANG Pan;LIU TianLin;CAI LianYun;LI HaiTao(Key Laboratory of Deep Oil and Gas Geology and Exploration,China University of Petroleum(East China),Qingdao 266580,China;School of Geosciences,China University of Petroleum(East China),Qingdao 266580,China;Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266071,China)

机构地区：[1]中国石油大学(华东)深层油气地质与勘探重点实验室,青岛266580 [2]中国石油大学(华东)地球科学与技术学院,青岛266580 [3]海洋国家实验室海洋矿产资源评价与探测技术功能实验室,青岛266071

出　　处：《地球物理学报》2020年第7期2751-2761,共11页Chinese Journal of Geophysics

基　　金：国家自然科学基金(41574118,41674131);中国石油重大科技项目(ZD2019-184-001);中央高校基本科研业务费专项资金(17CX06044);中国石油科技创新基金(2015D-5006-0303);国家科技重大专项(2017ZX05009-001)共同资助.

摘　　要：随钻地质导向钻井的关键在于对边界的探测,为提高仪器探测深度,时谐源激励的电磁波测井方法通常采用降低频率、增大源距的方式.瞬变电磁波测井信号源的突然关断产生会产生感应涡流,涡流随时间向地层深部扩散,与时谐源激励方式相比,其探测深度更大且测量过程不受信号源的干扰.因此,本文提出一种时间域瞬变电磁波测井边界远探测方法,采用余弦变换的数值滤波算法,模拟层状地层同轴发射接收线圈的瞬变电磁波测井响应,结果显示,地层电导率越大,电磁波传播速度越慢,测量晚期感应电动势与地层电导率线性相关;通过定义层状介质总场与线圈系所在当前层背景场的差值可方便提取界面信息,对界面的探测距离可达数十米;瞬变电磁波测井响应受源距的影响很小,为利用短源距实现远探测提供了可能.瞬变电磁波测井与时谐源电磁波测井相比优势明显,在电磁波测井领域中应用前景广阔.The key of geosteering in LWD is the detection of the boundary.In order to enhance the detection depth,the electromagnetic logging method excited by time-harmonic source usually adopts reduced frequency or increased source spacing.In this case,the sudden turn-off of the transient electromagnetic logging source can generate induced eddy currents,which diffuses deep into the formation over time.Compared with the time-harmonic source excitation method,its investigation depth is much larger and the measured transient signal encounters no interference because the transmitter is silent when the formation signal is acquired.Based on such a principle,this paper proposes a time-domain transient electromagnetic logging boundary detection method.It uses the cosine transform numerical filtering algorithm to simulate the transient electromagnetic logging response of the coaxial transmitting and receiving coil of layered formation.Results show that the larger of the formation conductivity,the slower the electromagnetic wave propagation velocity and there is a linear correlation between the measured late induced electromotive force and the formation conductivity.The interface information can be easily extracted by defining the difference between the total field of the layered formation and the background field where the coil system is placed at,and the investigation depth can reach several tens of meters.Meanwhile the transient electromagnetic logging response is less affected by coil spacing,which makes it possible to achieve deep detection by using short spacing.This transient electromagnetic logging method has obvious advantages compared with the electromagnetic logging method excited by time-harmonic source and has a broad application prospect in the field of electromagnetic logging.

关 键 词：瞬变电磁波测井 时间域 地层边界 远探测 源距 

分 类 号：P631[天文地球—地质矿产勘探]