Patent ID: 8991519
Filing Date: 2015-03-31
Classification: E21B,G01V

Abstract:
1. Apparatus for target proximity detection from a borehole being drilled, comprising: a drill string having multiple drill pipe sections connected end-to-end and carrying a drill bit; at least one of said drill pipe sections being electrically conductive to provide a drill pipe electrode section; at least one electrically insulating drill pipe sub electrically isolating said electrode section from adjacent drill pipe sections; a power supply in electrical communication with said at least one drill pipe electrode section and energizable to inject a time-varying current into Earth formations surrounding said borehole; a drill bit instrument at said drill bit comprising sensors for detecting magnetic fields produced by said injected current, said drill bit instrument including an other power supply and a down-hole control computer for processing magnetic field data received from the sensor; communicating the processed magnetic field data to surface instrumentation; and controlling power output by the other power supply based, at least in part, on the presence of output signals from the sensors; and control circuitry coupled to the power supply that energizes the power supply in response to a control signal from surface instrumentation.