Electromagnetic telemetry using active electrodes

Abstract

An electromagnetic (EM) telemetry system of a wellbore drilling and production environment includes at least one downhole sensor. The system also includes a downhole transceiver including an encoded signal transmitter. The encoded signal transmitter transmits data collected by the at least one downhole sensor. Further, the system includes an encoded signal receiver, which includes one or more active counter electrodes.

What is claimed is: 
     
         1 . An electromagnetic (EM) telemetry system of a wellbore drilling and production environment, the system comprising:
 at least one downhole sensor;   a downhole transceiver comprising an encoded signal transmitter, the encoded signal transmitter configured to transmit data collected by the at least one downhole sensor; and   an encoded signal receiver comprising one or more active counter electrodes.   
     
     
         2 . The system of  claim 1 , wherein the downhole sensor is communicatively coupled to the transceiver. 
     
     
         3 . The system of  claim 1 , wherein the encoded signal receiver is disposed at a surface of the wellbore drilling and production environment. 
     
     
         4 . The system of  claim 1 , wherein the encoded signal transmitter transmits an encoded signal comprising the data collected by the at least one downhole sensor. 
     
     
         5 . The system of  claim 1 , wherein the one or more active counter electrodes each comprise a galvanic electrode in series with an amplifier. 
     
     
         6 . The system of  claim 5 , wherein the galvanic electrode comprises a metal-metal salt porous pot. 
     
     
         7 . The system of  claim 5 , wherein the galvanic electrode comprises a metal rod, a metal plate, an adjacent well casing, or an abandoned wellhead. 
     
     
         8 . The system of  claim 5 , wherein the amplifier includes a negative feedback loop. 
     
     
         9 . The system of  claim 1 , wherein the one or more active counter electrodes are positioned beneath a surface of a formation. 
     
     
         10 . The system of  claim 1 , wherein the one or more active counter electrodes comprise at least two active counter electrodes, and the encoded signal receiver is configured to measure a potential difference between two of the at least two active counter electrodes. 
     
     
         11 . The system of  claim 1 , wherein one of the one or more active counter electrodes comprises an active wellhead of the wellbore drilling and production environment. 
     
     
         12 . The system of  claim 1 , wherein the one or more active counter electrodes are arranged in an array configuration. 
     
     
         13 . A method for communicating with a downhole transceiver, the method comprising:
 receiving a first encoded signal using an active counter electrode;   decoding the first encoded signal;   encoding a second encoded signal; and   transmitting the second encoded signal using the active counter electrode.   
     
     
         14 . The method of  claim 13 , wherein the first encoded signal carries data including one or more of measurement-while-drilling data and logging-while drilling data. 
     
     
         15 . The method of  claim 13 , wherein the second encoded signal carries data including instructions for downhole equipment coupled to the downhole transceiver. 
     
     
         16 . The method of  claim 13 , wherein receiving the first encoded signal comprises:
 receiving a first voltage signal at the active counter electrode;   receiving a second voltage signal at a wellhead; and   measuring a voltage difference between the first voltage signal and the second voltage signal.   
     
     
         17 . The method of  claim 13 , wherein the active counter electrode comprises a galvanic electrode in series with an amplifier. 
     
     
         18 . An electromagnetic (EM) telemetry system, comprising:
 at least one downhole sensor;   a downhole transceiver comprising an encoded signal transmitter, the encoded signal transmitter configured to transmit data collected by the at least one downhole sensor as an encoded signal into a formation; and   an encoded signal receiver comprising one or more active counter electrodes, the one or more active counter electrodes comprising a galvanic electrode in series with an amplifier and configured to receive the encoded signal from the formation.   
     
     
         19 . The system of  claim 18 , wherein the amplifier comprises a negative feedback loop. 
     
     
         20 . The system of  claim 18 , wherein the amplifier comprises an input impedance of between 500 kOhm and 10 MOhm.