Nuclear Magnetic Resonance Logging Inversion Method Of Discrete Spectrum

Nuclear magnetic resonance logging technology plays an irreplaceable role in modern petroleum exploration and development.During the interpretation of magnetic resonance logging data,the relaxation time distribution curve obtained by inversion can provide important geological information such as rock porosity,fluid saturation and permeability for oil and gas exploration.How to get a high resolution and accurate relaxation time spectrum is an important research topic in magnetic resonance logging.More and more attention has been paid to shale reservoir gas exploration.The matrix pencil method provides a new way for getting a transverse relaxation time spectrum of magnetic resonance logging.Based on aT₂ spectral model of shale reservoir,this paper studies the application of the matrix pencil method in magnetic resonance logging data interpretation.Numerical simulation and analysis indicate that the matrix pencil method applies to magnetic resonance logging of shale reservoirs.Also,we study the influences of NMR measurement parameters on the inversion,and we can draw the following conclusions:SNR,echo space,number of echoes and the number ofT₂ bins will affect the result of inversion.The result of inversion is consistent with the₂T spectrum model of shale in this paper while number ofT₂bins?2,number of echoes?128,SNR?30 and_ET?0.1ms.It is critical to find a proper truncate singular value for MPM.The purpose of this paper is to choose two regularization algorithms for the matrix pencil method which are L-curve and GCV.And numerical simulations indicate that these two methods can effectively select regularization parameters with SNR（28）50 and SNR（28）30.