Patent ID: 6098019
Filing Date: 2000-08-01
Classification: G01V

Abstract:
A method of determining electric resistivity of an earth formation surrounding a wellbore filled with a wellbore fluid, the method comprising:a) operating a resistivity logging tool in the wellbore so as to provide a plurality of resistivity logs of the earth formation for different radial distance intervals relative to the wellbore;b) for each radial distance interval, selecting a modelled resistivity profile;c) inputting the modelled resistivity profiles to a logging tool simulator so as to provide for each radial distance interval a modelled resistivity log having a depth of investigation corresponding to the radial distance interval;d) for each radial distance interval updating the modelled resistivity profile in dependence of an observed deviation of the resistivity log from the modelled resistivity log; ande) repeating steps c) and d) until for each radial distance interval the difference between the resistivity log and the corresponding modelled resistivity log is below a selected threshold value,characterized in that step d) comprises updating each modelled resistivity profile as a function of a ratio of the resistivity log to the modelled resistivity log pertaining to that radial distance interval.