Research on Multi-frequency Electromagnetic Well Logging:Simulation and Analysis

摘要

Electromagnetic well logging,also known as dielectric logging,can detect conductivity and permittivity constant around the borehole It has significant advantages over traditional resistivity logging in water flooded layer interpretation,secondary recovery of crude oil and enhanced oil recovery since it does not need any prior information of the resistivity of formation water..Currently,electromagnetic logging instruments mostly operate at single or dual frequencies.Dielectric Scanner,developed by Schlumberger,can measure formation's conductivity and permittivity simultaneously at different depths around borehole.It works at four discrete frequencies ranging from 20 MHz to 1 GHz.Referring to the Dielectric Scanner,a multi-frequency electromagnetic well logging model is established in this paper.It includes an articulated pad containing eight receiver antennas,two transmitter antennas borehole and formation with invaded zone.Finite Difference Time Domain (FDTD) method is used to simulate electromagnetic wave propagation in this model.After processing pulsed time-domain signal of different formations,the spatial sensitivity response and borehole affection are calculated.In addition,we give the charts converting the amplitude ratio and the phase difference to the conductivity and relative permittivity at different frequencies below 140 MHz.The results in this paper can provide guidance for further research on multi-frequency electromagnetic well logging.