Abstract: A method, drill string, bottomhole assembly, drill bit, and insert are for extending a borehole for a relief well in a subsurface. The rotary drill string is provided in the borehole and includes a bottomhole assembly. The bottomhole assembly includes a drill bit. Current is provided into the subsurface using at least one electrode on the drill string, thereby generating current in a casing of a mother well located a distance away from the borehole of the relief well. At least one component of a magnetic field associated with the current generated in the casing is detected using at least one sensor disposed on the drill string. Data is obtained from the sensor for determining either or both the proximity and direction to the mother well. The drill string is advanced into the subsurface based upon the obtained data to extend the borehole.

Abstract: A method, drill string, bottomhole assembly, drill bit, and insert are for extending a borehole for a relief well in a subsurface. The rotary drill string is provided in the borehole and includes a bottomhole assembly. The bottomhole assembly includes a drill bit. Current is provided into the subsurface using at least one electrode on the drill string, thereby generating current in a casing of a mother well located a distance away from the borehole of the relief well. At least one component of a magnetic field associated with the current generated in the casing is detected using at least one sensor disposed on the drill string. Data is obtained from the sensor for determining either or both the proximity and direction to the mother well. The drill string is advanced into the subsurface based upon the obtained data to extend the borehole.