Phasor processing of induction logs including shoulder and skin effect correction

摘要

A method and system for processing induction measurements of sub-surface formations taken by an induction logging system at various depths in a borehole is disclosed. The method reduces the unwanted contributions in the measurements from induction currents flowing in the formations spaced apart from each measurement depth (shoulder effect) and the effects of variations in the logging system transfer function with variations in the conductivity of the formations being investigated (skin effect). Shoulder effect is reduced by generating a spatial deconvolution filter which when convolved with the sonde response function sharpens the main lobe and reduces the sidelobes to near zero. The skin effect is reduced by filtering the quadrature-phase component measurements according to a non-linear spatial filtering function to obtain a correction component measurement representative of the change in the sonde response function as a function of the formation conductivity. The correction component measurements are then summed with the processed in-phase component measurements to produce a processed log measurement in which the unwanted contributions from shoulder effect and skin effect are reduced.