Patent ID: 6449561
Filing Date: 2002-09-10
Classification: G01V

Abstract:
A method of providing a computed induction log for an induction logging tool run through an interval of a wellbore that extends through a layered formation which formation is invaded by wellbore fluid, which method comprises the steps of:(a) computing a first response of the induction logging tool by solving for each formation layer the Maxwell equations for the electromagnetic field with known logging tool properties, wellbore diameter, wellbore fluid resistivity, diameter of the invaded zone, and resistivity of the invaded zone and of the formation layer outside the invaded zone, using a one-dimensional concentric cylinder model not taking into account the effects of formation layering and of the orientation of the logging tool with respect to the formation layering, and determining for each formation layer an equivalent resistivity that gives for a homogeneous environment a response of the induction logging tool that equals the first response; and (b) computing for a number of logging points solutions of the Maxwell equations for the electromagnetic field with the known logging tool properties and the equivalent resistivities for the formation layers, using a one-dimensional layered model wherein the effects of the formation layering and of the orientation of the logging tool with respect to the formation layering are taken into account, to provide the computed induction log of the induction logging tool.