Well location determination apparatus, methods, and systems

A system, comprising:

• a downhole tool;
• at least one of a magnetometer or an electric field antenna located proximate to each one of a set of three or more existing well casings, the at least one of the magnetometer or the electric field antenna to provide a set of signals;
• and
• a signal processor to monitor the set of signals representing changes in at least one of a magnetic field or an electric field perturbed by current induced in a drillstring coupled to the downhole tool and located in a well under construction, and to determine a location of the well under construction in relation to the set of existing well casings based on the changes.

A processor-implemented method to execute on one or more processors that perform the method, comprising:

• launching a set of currents into a corresponding set of three or more existing well casings, wherein each of the existing well casings is associated with a corresponding current launching apparatus to launch one of the set of currents;
• monitoring, 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
• determining a location of the well under construction in relation to the set of existing well casings based on the changes.

A processor-implemented method to execute on one or more processors that perform the method, comprising:

• inducing current into a drillstring located in a well under construction;
• monitoring, at a set of three or more 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, wherein each of the existing well casings is associated with corresponding measurement instrumentation to conduct the monitoring;
• and
• determining a location of the well under construction in relation to the set of existing well casings based on the changes.

An article including a non-transitory machine-readable medium having instructions stored therein, wherein the instructions, when executed, result in a machine performing:

• launching a set of currents into a corresponding set of three or more existing well casings, wherein each of the existing well casings is associated with a corresponding current launching apparatus to launch one of the set of currents;
• monitoring, 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
• determining a location of the well under construction in relation to the set of existing well casings based on the changes.

An article including a non-transitory machine-readable medium having instructions stored therein, wherein the instructions, when executed, result in a machine performing:

• inducing current into a drillstring located in a well under construction;
• monitoring, at a set of three or more 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, wherein each of the existing well casings is associated with corresponding measurement instrumentation to conduct the monitoring;
• and
• determining a location of the well under construction in relation to the set of existing well casings based on the changes.