Abstract: A method to guide a drilling path of a second well in proximity to a first well including: applying a time-varying electrical current to a conductive casing or liner of the first well; from the drilling path of the second well, sensing an electromagnetic field generated by the current in the first well, and guiding the drilling path trajectory of the second well using the sensed electromagnetic field.

Abstract: A method to guide a drilling path of a second well in proximity to a first well including: applying a time-varying electrical current to a conductive casing or liner of the first well; from the drilling path of the second well, sensing an electromagnetic field generated by the current in the first well, and guiding the drilling path trajectory of the second well using the sensed electromagnetic field.

Abstract: System and methods for guiding the drilling of a horizontal well are disclosed. A current is provided in at least one conductor positioned in a target vertical well. A magnetic field generated by the current is measured at a drilling assembly that is drilling the horizontal well. A direction from the drilling assembly to the target vertical well is determined based at least in part on the measured magnetic field. A distance from the drilling assembly to the target vertical well is determined based at least in part on the measured magnetic field. The determination of the distance includes determining at least one gradient.

Abstract: System and methods for guiding the drilling of a horizontal well are disclosed. A current is provided in at least one conductor positioned in a target vertical well. A magnetic field generated by the current is measured at a drilling assembly that is drilling the horizontal well. A direction from the drilling assembly to the target vertical well is determined based at least in part on the measured magnetic field. A distance from the drilling assembly to the target vertical well is determined based at least in part on the measured magnetic field. The determination of the distance includes determining at least one gradient.

Abstract: A bidirectional drilling downhole steering and survey tool for detecting ferromagnetic bodies from an off vertical borehole, transmitting the signals from the downhole sensors to surface equipment while drilling, and for calculation of the range and direction to the detected ferromagnetic body for the use of the directional driller in intercepting or avoiding the ferromagnetic body. In combination with the steering and range and direction to ferromagnetic body capabilities, the downhole tool may also include sensors for detecting formation bed interface, apparatus for electric or gamma ray or radioactive logging, neutron density sensor apparatus and other formation evaluation or correlation apparatus. The downhole tools may be packaged, in either an electric line transmitted tool of MWD transmitted tool.

Abstract: A directional drilling downhole steering and survey tool for detecting ferromagnetic bodies from an off vertical borehole, transmitting the signals from the downhole sensors to surface equipment while drilling, and for calculation of the range and direction to the detected ferromagnetic body for the use of the directional driller in intercepting or avoiding the ferromagnetic body. In combination with the steering and range and direction to ferromagnetic body capabilities, the downhole tool may also include sensors for detecting formation bed interface, apparatus for electric or gamma ray or radioactive logging, neutron density sensor apparatus and other formation evaluation or correlation apparatus. The downhole tools may be packaged in either an electric line transmitted tool of MWD transmitted tool.

Abstract: A method and apparatus for performing a surveying operation to locate a target subterranean ferromagnetic body having remanent or impressed magnetization. The surveying operation is conducted from an off-vertical borehole adjacent the target magnetic body using magnetic field sensing apparatus, and involves determining the range and direction of the subterranean target with respect to the location of the magnetic field sensing apparatus. Target direction is determined by measuring three magnetic field components and resolving the measured components into a resultant vector. Target range is determined by measuring total magnetic field intensity and target body magnetic field intensity gradient in the direction of the off-vertical borehole. Both static and time-varying fields may be detected by the subsurface apparatus.