Patent ID: 6487782
Filing Date: 2002-12-03
Classification: E21B

Abstract:
A method for creating a magnetic declination profile for a borehole comprising the steps of:(a) making a first magnetic directional measurement at a first longitudinal location in the borehole, wherein the first magnetic directional measurement is influenced by magnetic flux and wherein the first magnetic directional measurement is made at a first magnetic measurement orientation; (b) making a first reference directional measurement in the borehole, wherein the first reference directional measurement is not influenced by magnetic flux, wherein the first reference directional measurement is made at a first reference measurement orientation, wherein there is a first orientation relationship between the first magnetic measurement orientation and the first reference measurement orientation and wherein the first orientation relationship is known or ascertainable; and (c) obtaining a value of magnetic declination at the first longitudinal location in the borehole using the first magnetic directional measurement, the first reference directional measurement and the first orientation relationship.