Patent ID: 8718942
Filing Date: 2014-05-06
Classification: G01V

Abstract:
1. A method of investigating a formation surrounding a borehole, comprising: at least one processor configured to computing both an average in-phase current and an average out-of-phase current for each pad disposed on a down-hole tool by repeatedly acquiring in-phase and out-of-phase current data from the formation relative to a voltage applied to one or more electrodes disposed on said pad over multiple depths within a depth window and averaging the acquired in-phase and out-of-phase current data over the one or more electrodes, so as to obtain the average in-phase current and the average out-of-phase current for each pad at each depth of the multiple depths within the depth window; determining an average phase shift compensation angle from each respective phase shift compensation angle calculated for each pad of the down-hole tool by estimating a slope of a fitted line that passes through a distribution of data points of a cross plot of the computed average in-phase currents and the computed average out-of-phase currents for each pad accumulated within the depth window, the phase shift compensation angle is taken to be the slope angle of the fitted line; applying the average phase shift compensation angle determined to in-phase and out-of-phase current data subsequently acquired by each pad of the down-hole tool from the formation over a depth of the borehole to be measured, so as to obtain phase shift compensated current values over the depth of the borehole to be measured; and forming an image of the borehole based on the phase shift compensated current values obtained.