System and method for performing inversion on lwd resistivity logs with

Abstract

A system and method for performing inversion and for correcting for shoulder bed effect. The method enhances the resolution of wave propagation resistivity logs and corrects the logs for adjacent bed effects, whereby the resulting logs have a vertical response as good as wireline high-resolution induction logs. The method first performs logging while drilling on a formation to obtain LWD resistivity log data. The method then selects one or more control depths at one or more locations of each of a plurality of detected beds in the formation. The present invention includes a novel method for selecting bed boundaries from the log data, and the control depths are then determined based on the determined bed boundaries. The method then estimates the resistivity of each bed only at the selected control depths to produce an estimated resistivity of the beds. The method then computes a simulated log value at each control depth using a current estimate of the resistivity of the beds. The computed simulated log, is then compared to the actual log data at each control depth, and the resistivity of each bed is adjusted using the difference between the actual and simulated values at the control depths. The above method iteratively repeats a plurality of times until the simulated log substantially matches the actual log at the control depths.