US 4,739,325 AGranted

Apparatus and method for down-hole EM telemetry while drilling

AssigneeMacLeod Laboratories, Inc.

InventorNorman C. MacLeod

Life of this patent

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Abstract

An MWD EM data/control telemetry link between down-hole instruments and ground surface instruments dynamically adapts to the underground electrical environment utilizing a down-hole microprocessor unit and a surface data processing unit (computer) each of which continuously monitors, probes and sweeps the frequency spectrum with EM signals to determine an optimum frequency for signal transmission between the respective units via either the drill string, the surrounding strata, or both, and then generates and digitally modulates a carrier signal at such optimum frequency with data/control signals. A particular feature of the communication system is a combination of a sensing toroid and insulated gaps interrupting electrical continuity so as to force all currents propagating in the strata and pipe string to flow through the axial opening of the sensing toroid via a conduction path dictated by considerations of electrical design rather than by mechanical constraints, thus enabling the effective electrical length of the drill string below the down-hole module to be optimized.

Claims20

Dependent claims

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.

6 more elements

An electromagnetic (EM) wave telemetry system for communicating data from down-hole sensing devices contained in a down-hole module in a very deep well to a ground surface station comprising, in combination:

(a) an electrically conductive pipe string mechanically coupling the down-hole module to the surface station;
(b) a down-hole electrical current generator contained in said down-hole module for generating an alternating electromagnetic (EM) transmission current in the pipe string and underground strata;
(c) module frequency control means operatively coupled to said down-hole current generator for controllably causing said down-hole current generator to generate EM transmission currents over a range of frequencies;
(d) surface receiver means for detecting which particular frequency of the EM transmission currents generated by said down-hole current generator produces an EM transmission current having a first particular characteristic as detected at ground surface;
(e) a surface electrical current generator for producing a first EM transmission current in said pipe string and underground strata corresponding in frequency to that of the detected EM transmission current having said first particular characteristic;
(f) down-hole receiver means for receiving said first EM transmission current generated by said surface generator and for causing said down-hole current generator to generate a second EM transmission current at the frequency of said detected EM transmission current;
(g) analogue-to-digital (A/D) means for converting analogue data signals developed by said down-hole sensing devices into digital electrical data signals;
(h) down-hole microprocessor means located in said down-hole module for receiving said digital data signals and for 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 said digital data signals into digital transmission data signals;
(i) down-hole modulator means for modulating said first EM transmission current with said digital transmission data signals, said surface receiver means being operative to detect the modulated first EM transmission current at ground surface;
(j) surface demodulator means for receiving output signals developed by said surface receiver means and for converting the detected modulated EM transmission current into a digital data string;
(k) a surface data processor means for receiving 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 reflecting down-hole conditions detected by said down-hole sensing devices.

8 more elements

Dependencies are inferred from the claim text.

Facts

Application: 06/838,639Filed 6 Mar 1986 · continuation in part
Priority: 9 Sep 1982
Granted: 19 Apr 1988
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

E21B 47/13
Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging…
E21B 17/003
Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings: with electrically conducting or…
G01V 3/24
Operating with propagation of electric current: using AC
E21B
Earth or rock drilling