# US 2013/0154844 A1 · Methods for clock synchronization in wellbore instruments

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- Number: US 2013/0154844 A1
- Document ID: US20130154844A1
- Status: Published application
- Kind: A1
- Application number: 13/769,055
- Filed: 2013-02-15
- Published: 2013-06-20
- Earliest claimed: 2009-05-26
- Assignees: IntelliServ, Inc.
- Inventors: Michael A. Montgomery; Julius Kusuma
- Web page: https://patentgrep.com/patent/US20130154844A1

## CPC

- G01V 3/18: specially adapted for well-logging
- G01V 1/26: Reference-signal-transmitting devices, e.g. indicating moment of firing of shot
- G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02)

## Abstract

A method for synchronizing a clock in a device at the Earth's surface with a device disposed in a wellbore includes generating a time datum for a signal generated at at least one of the surface and in the wellbore proximate an end of the pipe string. A time delay is determined between detection of the signal at the at least one repeater and retransmission of the signal from the at least one repeater. The time datum is appended with a signal corresponding to the time delay. The retransmitted signal is detected at the other of proximate the end of the pipe string and at the surface.

## Claims

### Claim 1

A method for synchronizing clocks in a wellbore instrument, comprising:
generating a clock signal at a first clock;
detecting the clock signal at a second clock; and
adjusting a timing of the second clock corresponding to the clock signal, the clock signal having an autocorrelation function narrower in time than a period of the clock signal, the detecting comprising at least one of correlation, peak detection and threshold detection.

### Claim 2 (depends on 1)

The method of claim 1 wherein the clock signal comprises a pseudorandom sequence.

### Claim 3 (depends on 1)

The method of claim 1 wherein the clock signal comprises a baseband signal.

### Claim 4 (depends on 1)

The method of claim 1 wherein the clock signal comprises a passband signal.

### Claim 5 (depends on 1)

A system including the method of claim 1, further comprising:
a clock generator to generate the clock signal at the first clock;
a receiver to detect the clock signal at the second clock; and
a calculator in the receiver to adjust the timing of the second clock corresponding to the clock signal.

### Claim 6

A system for synchronizing clocks in a wellbore instrument comprising:
a clock generator in a first clock to generate a clock signal at the first clock;
a receiver to detect the clock signal at the second clock; and
a calculator in the receiver to adjust the timing of the second clock corresponding to the clock signal, the clock signal having an autocorrelation function narrower in time than a period of the clock signal, the receiver comprising at least one of correlation, peak detection and threshold detection.

### Claim 7 (depends on 6)

The system of claim 6 wherein the clock signal comprises a pseudorandom sequence.

### Claim 8 (depends on 6)

The system of claim 6 wherein the clock signal comprises a baseband signal.

### Claim 9 (depends on 6)

The system of claim 6 wherein the clock signal comprises a passband signal.