Patent ID: 9360580
Filing Date: 2016-06-07
CPC Classification: E21B,G01V

Claim Text:
1. A method of electromagnetic resistivity measurement to determine distance and direction to a boundary within a formation, comprising: deploying a conductive tubular in a wellbore in a first formation having a first resistivity, the conductive tubular having a drill bit that axially extends the wellbore, a gap, and a magnetometer configured to receive a magnetic signal from an adjacent formation having a contrasting resistivity; while axially extending the wellbore in the first formation, generating a current along the conductive tubular and across the gap wherein the current induces a primary magnetic field arising from the current in the tubular, the current leaking into the first formation and induces a secondary magnetic field; measuring a direction of the secondary magnetic field; determining a direction of the adjacent formation from the direction of the secondary magnetic field; measuring a magnitude of the secondary magnetic field; and determining a distance to the adjacent formation wherein the wellbore does not pass based on a non-zero magnitude of the measured secondary magnetic field and is steered away from the adjacent formation.