Methods for improved active ranging and target well magnetization

摘要

A method for magnetizing a portion of a pre-deployed casing string includes deploying an electromagnetic array in a cased wellbore and energizing the array. The array includes a plurality of axially spaced electromagnets and is configured to generate a magnetic field pattern having at least first and second pairs of magnetically opposing poles. Passive ranging measurements of the induced magnetic field may be advantageously utilized, for example, to survey and guide continued drilling of a twin well. The electromagnetic array may also be used in active ranging applications. An array of permanent magnets providing a similar magnetic field pattern may also be used in active ranging applications.