System For Wireless Communication Along A Drill String

Abstract

A wireless communication and drill string telemetry system. The communication system is used for communicating information along a drill string between a boring tool and a boring machine. An insulator assembly provides an electrically insulated gap between the drill string communication path and a soil engaging electrode for the electrical return path. A transmitter assembly includes a data transmitter for encoding and transmitting a data signal. A signal coupler couples the data signal to the drill string and provides a controlled electrical connection between the drill string communication path and the soil engaging electrode. The signal coupler comprises a transformer and a current regulating circuit to adjust a voltage across the transformer's primary winding. A receiver assembly is disposed proximate the drilling machine and includes a toroidal pickup coil and a signal processing assembly. The pickup coil has an annulus and is positioned such that the drill string communication path passes through the annulus. The pickup coil produces a signal voltage in response to a signal current on the drill string that the signal processing assembly processes to extract the data signal.

1 . A signal coupler adapted for use with a drill string communication system, the signal coupler adapted to provide a controlled electrical connection between the drill string and a soil engaging electrode, the signal coupler comprising:
 a transformer having a winding; and   a control circuit adapted to adjust a control signal across the winding to maintain a desired current amplitude in the controlled electrical connection.   
     
     
         2 . The coupler of  claim 1  wherein the transformer comprises a secondary winding. 
     
     
         3 . The coupler of  claim 2  wherein a first side of the secondary winding is connected to the drill string and a second side of the secondary winding is connected to the soil engaging electrode. 
     
     
         4 . The coupler of  claim 1  wherein the transformer comprises a unity gain isolation transformer. 
     
     
         5 . The coupler of  claim 1  wherein the transformer further comprises a current-sampling winding and wherein the regulating circuit is adapted to adjust a voltage across the primary winding to maintain substantially constant signal amplitude in the current-sampling winding. 
     
     
         6 . The coupler of  claim 1  wherein the transformer comprises a step-down transformer. 
     
     
         7 . The coupler of  claim 1  wherein the control circuit comprises a regulating circuit. 
     
     
         8 . The coupler of  claim 7  wherein the regulating circuit is chosen from the group consisting of a voltage regulating circuit, a current regulating circuit, and a control impedance circuit. 
     
     
         9 . The coupler of  claim 1  wherein the control signal comprises a voltage. 
     
     
         10 . A drill string communication system comprising:
 a drill string;   a soil engaging electrode; and   a signal coupler for providing an electrical connection between the drill string and the soil engaging electrode, the signal coupler comprising a winding.   
     
     
         11 . The system of  claim 10  further comprising:
 a data transmitter assembly to encode and transmit a data signal along the drill string; and 
 a receiver assembly to process and extract the data signal. 
 
     
     
         12 . The system of  claim 11  further comprising a regulating circuit adapted to adjust a voltage across the winding to maintain an acceptable bit error rate at the receiver assembly. 
     
     
         13 . The system of  claim 10  further comprising a regulating circuit adapted to adjust an operating parameter across the winding to maintain a substantially constant signal amplitude in the winding. 
     
     
         14 . The system of  claim 10  wherein the signal coupler further comprises an insulator assembly, the insulator assembly defining an electrically insulated gap between the drill string and the soil engaging electrode. 
     
     
         15 . A system for data communication in a drilling operation, the system comprising:
 a drill string;   a soil-engaging electrode;   a transmitter assembly adapted to transmit a signal comprising a data signal along the drill string;   a receiver assembly to detect the signal and extract the data signal.   
     
     
         16 . The system of  claim 15  wherein the signal comprises a electrical current. 
     
     
         17 . The system of  claim 15  further comprising an electrically insulated gap between the drill string and the soil engaging electrode. 
     
     
         18 . The system of  claim 15  wherein the receiver assembly comprises a pickup coil to produce a signal voltage in response to the signal on the drill string. 
     
     
         19 . The system of  claim 18  wherein the pickup coil defines a toroid. 
     
     
         20 . The system of  claim 15  wherein the transmitter assembly is located at a downhole end of the drill string. 
     
     
         21 . The system of  claim 20  further comprising:
 a second transmitter assembly located at an uphole end of the drill string; and 
 a second receiver assembly located at a downhole end of the drill string. 
 
     
     
         22 . A method for communicating information along a drill string comprising:
 insulating a first end of a drill string from second end of the drill string;   generating a signal on the first end of the drill string using a transformer having a winding;   maintaining a substantially constant signal amplitude in the winding; and   extracting the signal at the second end of the drill string.   
     
     
         23 . The method of  claim 22  further comprising adjusting a control signal across the primary winding to reduce bit errors. 
     
     
         24 . The method of  claim 22  wherein the signal is encoded in a signal current. 
     
     
         25 . The method of  claim 23  wherein the control signal comprises a voltage.