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Apparatus and method for down-hole EM telemetry while drilling

  • US 4,739,325 A
  • Filed: 03/06/1986
  • Issued: 04/19/1988
  • Est. Priority Date: 09/30/1982
  • Status: Expired due to Term
First Claim
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1. A method for communicating data from down-hole sensing devices contained in a down-hole module incorporated into a conductive drill string to ground surface comprising the steps of:

  • (a) generating a first alternating electromagnetic (EM) transmission current in the drill string and underground strata with an electrical current generator disposed within the module;

    (b) detecting the frequency of said generated first EM transmission current that produces a particular EM transmission current level at ground surface;

    (c) setting said electrical current generator to generate a second EM transmission current at the detected frequency;

    (d) converting analogue data signals developed by said down-hole sensing devices into digital electrical data signals;

    (e) inputting said digital data signals into a down-hole microprocessor means located in the down-hole module, and logically operating on said digital data signals according to a first program stored in a first programmable read only memory (PROM), a first random access memory (RAM), and a first electrically erasable programmable read only memory (EEPROM) to convert such digital signals into digital transmission data signals;

    (f) modulating said second EM transmission current with said digital transmission data signals;

    (g) detecting the modulated second EM transmission current at ground surface;

    (h) converting the detected modulated second EM transmission current into a digital data string;

    (i) inputting said first digital data string into a surface data processor means and logically operating on said digital data string according to a second program stored in a second programmable read only memory (PROM), a second random access memory (RAM) and a second electrically erasable programmable read only memory (EEPROM) to convert said digital data string into analogue data signals reflecting conditions of the down-hole strata detected by said down-hole sensing devices.

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