Patent ID: 6765386
Filing Date: 2004-07-20
Classification: G01V

Abstract:
A method for measuring resistive anisotropy of a formation, the method comprising:inserting a logging tool in a well bore that penetrates the formation, wherein the logging tool has at least one set of electrodes that contact a well bore wall; driving a current between a vertically-spaced electrode pair; determining a vertical voltage difference between two vertically-spaced measurement points located between the vertically-spaced electrode pair; driving a current between a horizontally-spaced electrode pair; determining a horizontal voltage difference between two horizontally-spaced measurement points located between the horizontally-spaced electrode pair; multiplying the vertical voltage difference with a first tool coefficient to determine an apparent vertical resistivity; and multiplying the horizontal voltage difference with a second tool coefficient to determine an apparent horizontal resistivity; and calculating a formation anisotropy from a ratio of the apparent horizontal resistivity to the apparent vertical resistivity.