Abstract: A tool, method and system for ranging between two wellbores. The target wellbore includes a conductive member disposed within a portion of the target wellbore. An investigative wellbore includes an electromagnetic gradiometer positioned within the wellbore, as well as emitter electrode and return electrode spaced apart along an investigative wellbore, preferably in the process of being drilled. The position of the emitter electrode and the return electrode are selected to optimize current transmission to the target wellbore in order to enhance the electromagnetic field emanating from the conductive member at a desired point along the conductive member. Where the electrodes and gradiometer are carried by a drill string, gap subs are positioned along the drill string to minimize conduction of current along the drill string therebetween. In some embodiments, the gradiometer is positioned between the emitter and return electrodes.

Abstract: A rotationally independent wellbore ranging system includes a housing which is attached to a rotary component positioned in a first wellbore and remains substantially stationary relative to the first wellbore when the rotary component rotates in the first wellbore. Multiple sensors affixed to the housing are operable to receive multiple ranging signals from a second wellbore while the rotary component rotates in the first wellbore, and provide the multiple ranging signals to a processor to determine a position of the first wellbore relative to the second wellbore.

Abstract: A tool, method and system for ranging between two wellbores. The target wellbore includes a conductive member disposed within a portion of the target wellbore. An investigative wellbore includes an electromagnetic gradiometer positioned within the wellbore, as well as emitter electrode and return electrode spaced apart along an investigative wellbore, preferably in the process of being drilled. The position of the emitter electrode and the return electrode are selected to optimize current transmission to the target wellbore in order to enhance the electromagnetic field emanating from the conductive member at a desired point along the conductive member. Where the electrodes and gradiometer are carried by a drill string, gap subs are positioned along the drill string to minimize conduction of current along the drill string therebetween. In some embodiments, the gradiometer is positioned between the emitter and return electrodes.

Abstract: In one example of a rotationally independent wellbore ranging system, a housing attached to a rotary component is positioned in a first wellbore and remains substantially stationary relative to the first wellbore when the rotary component rotates in the first wellbore. Multiple sensors affixed to the housing are operable to receive multiple ranging signals from a second wellbore while the rotary component rotates in the first wellbore, and provide the multiple ranging signals to a processor to determine a position of the first wellbore relative to the second wellbore.

Abstract: An example method includes polling a plurality of reference nodes distributed along one or more reference wells. The method also includes steering a bottomhole assembly in another well based at least in part on information obtained from said polling. A related system includes a plurality of reference nodes distributed along one or more reference wells. The system also includes a bottomhole assembly in another well. The system also includes a surface controller. The surface controller polls the plurality of reference nodes to obtain position information regarding the bottomhole assembly and directs a steering module of the bottomhole assembly based on the obtained position information.

Abstract: A borehole array for ranging and crosswell telemetry is disclosed along with certain methods for employing such a borehole array. Some embodiments of the borehole array include electrically coupled reference nodes distributed along the length of a reference well. Each reference node includes a solenoid operated by a control unit. The control unit employs the solenoid to generate a magnetic field for guiding a bottomhole assembly in a nearby well. The control unit further serves as a communications intermediary between the bottomhole assembly and a surface facility. The bottomhole assembly can be guided in turn by subsequent reference nodes of the array and employ the closest reference node as a communications link to the surface. Moreover, the use of multiple reference nodes offers greater precision in determining the bottomhole assembly's position relative to the reference well. The borehole array can be used to guide multiple drilling operations concurrently.

Abstract: In some embodiments, apparatus and systems, as well as methods, may operate to launch a set of currents into a corresponding set of existing well casings; monitor, in a well under construction, changes in at least one of a magnetic field or an electric field perturbed by the set of currents after each one of the set is launched; and determine a location of the well under construction in relation to the set of existing well casings. In some embodiments, the activities include inducing current into a drillstring located in a well under construction; monitoring, at a set of existing well casings, changes in at least one of a magnetic field or an electric field perturbed by the current after the current is induced; and determining a location of the well under construction in relation to the set of existing well casings. Additional apparatus, systems, and methods are disclosed.

Abstract: In some embodiments, apparatus and systems, as well as methods, may operate to launch a set of currents into a corresponding set of existing well casings; monitor, in a well under construction, changes in at least one of a magnetic field or an electric field perturbed by the set of currents after each one of the set is launched; and determine a location of the well under construction in relation to the set of existing well casings. In some embodiments, the activities include inducing current into a drillstring located in a well under construction; monitoring, at a set of existing well casings, changes in at least one of a magnetic field or an electric field perturbed by the current after the current is induced; and determining a location of the well under construction in relation to the set of existing well casings. Additional apparatus, systems, and methods are disclosed.

Abstract: A borehole array for ranging and crosswell telemetry is disclosed along with certain methods for employing such a borehole array. Some embodiments of the borehole array include electrically coupled reference nodes distributed along the length of a reference well. Each reference node includes a solenoid operated by a control unit. The control unit employs the solenoid to generate a magnetic field for guiding a bottomhole assembly in a nearby well. The control unit further serves as a communications intermediary between the bottomhole assembly and a surface facility. The bottomhole assembly can be guided in turn by subsequent reference nodes of the array and employ the closest reference node as a communications link to the surface. Moreover, the use of multiple reference nodes offers greater precision in determining the bottomhole assembly's position relative to the reference well. The borehole array can be used to guide multiple drilling operations concurrently.