US 2003/0197510 A1 · Galvanic method of measuring electrical anisotropy

Abstract

A logging tool is disclosed for measuring the resistive anisotropy of formations around a borehole. The logging tool includes a set of electrodes that contact a wall of the borehole. The set of electrodes includes a first pair of current electrodes spaced apart vertically, and a second pair of current electrodes spaced apart horizontally. Between the first and second pair of current electrodes are two or more measurement electrodes that measure a vertical axis voltage difference and a horizontal axis voltage difference caused by currents flowing between the pairs of current electrodes. A resistive anisotropy can be calculated from the measured voltage differences. A third pair of current electrodes oriented perpendicularly with respect to the first and second pair of current electrodes may be provided with corresponding measurement electrodes if it is desired to measure the biaxial resistive anisotropy of the formation.

Claims20

Dependent claims

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;
and
determining a horizontal voltage difference between two horizontally-spaced measurement points located between the horizontally-spaced electrode pair.

3 more elements

A system for measuring the resistive anisotropy of earth formations surrounding a borehole, wherein the system comprises:

a logging tool having a set of electrodes that contact a wall of the borehole, wherein the set includes:
a first pair of electrodes spaced apart along a first axis;
two or more measurement electrodes spaced apart along the first axis between the first pair of electrodes;
a second pair of electrodes spaced apart along a second axis substantially perpendicular to the first axis;
and
two or more measurement electrodes spaced apart along the second axis between the second pair of electrodes;
and
a surface unit configured to receive periodic measurements of a first axis voltage difference as indicated by the two or more measurement electrodes spaced apart along the first axis when a current is driven between the first pair of electrodes, and to receive periodic measurements of a second axis voltage difference as indicated by the two or more measurement electrodes spaced apart along the second axis when a current is driven between the second pair of electrodes.

5 more elements

Dependencies are inferred from the claim text.

Galvanic method of measuring electrical anisotropy

Life of this patent

Galvanic method of measuring electrical anisotropy

Life of this patent

Abstract

Claims20