Electromagnetic borehole telemetry system incorporating a conductive borehole tubular

A measurement-while-drilling system for measuring a parameter of interest within a borehole, said system comprising:

• (a) a downhole assembly comprising a sensor, wherein said downhole assembly is terminated at lower end by a drill bit and at an upper end by a drill string operationally attached to a drilling rig;
• (b) an electromagnetic telemetry system for transmitting an electromagnetic signal indicative of a response of said sensor, said telemetry system comprising
• (i) a borehole EM transceiver,
• (ii) a surface EM transceiver,
• (iii) a first signal wire with a first end comprising first electrode disposed within said borehole and a second end electrically connected to said surface EM transceiver,
• (iv) a second signal wire with a first end comprising a second electrode disposed within said borehole and electrically connected to formation traversed by said borehole and a second end electrically connected to said surface EM transceiver, wherein
• (v) a measure of electric potential is made between said first and said second electrodes thereby forming said signal;
• and
• (c) a processor cooperating with said surface EM transceiver by means of a link to convert said signal into said parameter of interest.

A method for transmitting an electromagnetic signal within a borehole traversing a formation, the method comprising the steps of:

• (a) disposing a borehole EM transceiver within said borehole;
• (b) disposing a surface EM transceiver above said borehole EM transceiver;
• (c) disposing within said borehole a first signal wire with a first end comprising first electrode and a second end electrically connected to said surface EM transceiver;
• (d) disposing within said borehole a second signal wire with a first end comprising a second electrode disposed within said borehole and a second end electrically connected to said surface EM transceiver;
• (e) measuring an electric potential between said first and said second electrodes thereby forming said signal;
• and
• (f) transmitting said signal between said surface EM transceiver and said borehole EM transceiver via said first and said second signal wires.

A measurement-while-drilling method for measuring a parameter of interest in a borehole, said method comprising:

• (a) providing a downhole assembly comprising a sensor, wherein said downhole assembly is terminated at lower end by a drill bit and at an upper end by a drill string operationally attached to a drilling rig;
• (b) transmitting a signal indicative of a response of said sensor with a telemetry system comprising
• (i) a borehole EM transceiver,
• (ii) a surface EM transceiver,
• (iii) a first signal wire with a first end comprising first electrode disposed within said borehole and a second end electrically connected to said surface EM transceiver, and
• (iv) a second signal wire with a first end comprising a second electrode electrically connected to formation traversed by said borehole and a second end electrically connected to said surface EM transceiver;
• (c) measuring an electric potential between said first and said second electrodes thereby forming said signal;
• and
• (d) converting said signal into said parameter of interest with a processor cooperating with said surface EM transceiver by means of a link.