Patent ID: 8596382

Claim:
A method comprising: drilling a new well in a field having an existing well using a bottom hole assembly (BHA) having a drill collar divided by an insulated gap wherein the new well and the existing well are non-intersecting; generating a current along the drill collar of the BHA while drilling the new well to form an electric dipole over the insulated gap, the dipole having a first pole and a second pole; calculating a magnetic field strength for the electric dipole for a range of locations, wherein one of the first pole and the second pole has a truncated length with respect to the other; at the existing well, measuring a magnetic field caused by the electric dipole on the drill collar of the BHA; comparing the calculated magnetic field strength to the measured magnetic field; and determining a position of the new well relative to the existing well based on the comparing of the calculated magnetic field strength to the measured magnetic field.