摘要
The maximum distance at which an electromagnetic(EM)logging while drilling(LWD)tool detects an approaching boundary is defined as the depth of detection(DOD).Ultra-deep detection capability of the transient multicomponent EM logging measurement is investigated here.First,we adopt sine and cosine transform to calculate the transient multicomponent responses.Compared to the cosine transform,sine transform is more accurate in solving late-time responses.Then,a time-domain geosignal is introduced to sense the boundary.Results show that DOD of this transient EM measurement can be up to tens of meters,including directionally sensitivity.Additionally,by studying the decay characteristics of different components with time,cross component is confirmed to decay much faster than the coaxial/coplanar components in the formation coordinate system.A pseudo-inversion is thereby proposed to determine the dip angle of anisotropic stratified formation.Theoretical simulation results indicate that this algebraic method can determine the true dip at some particular moments.It is still stable and valid even when considering random measurement errors.Moreover,we establish the linear relationship between the time at which the half-point of geosignal curve appears and the distance to boundary(DTB),which would assist in the quick determination of DTB.
基金
the financial support from the National Natural Science Foundation of China(42074134,41974146,41574118)
the Scientific and Technological Research Projects of Sinopec(JP22503,P21080)
the Major Scientific and Technological Projects of China National Petroleum Corporation(ZD2019-184-001)
Shandong Provincial Natural Science Foundation(ZR2020MD050)
作者简介
Corresponding author:Shao-Gui Deng,E-mail address:dengshg@upc.edu.cn
