Interference reduction method for downhole telemetry systems

• US 8,942,330 B2
• Filed: 01/18/2012
• Issued: 01/27/2015
• Est. Priority Date: 01/18/2012
• Status: Active Grant

• Current Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Original Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Inventors: Zheng, Feng, Brahim, Imed Ben, Emmerich, Wojciech, Hansen, Christian, Bruns, Jens-Uwe, Moghaddamnia, Sanam
• Primary Examiner(s): LEE, SIU M
• Application Number:
  US13/352,714
• Publication Number:
  US 20130181843A1
• Time in Patent Office: 1,105 Days
• Field of Search: 375/346, 375/316, 375/350, 375/259, 375/285, 367/81, 370/286, 340/853.2, 455/63.1
• US Class Current: 375/346
• CPC Class Codes: E21B 47/18 through the well fluid , e.g. mud pressure pulse telemetry
• CPC Class Codes: G01V 11/002 Details, e.g. power supply systems for logging instruments, transmitting or recording data, specially adapted for well logging, also if the prospecting method is irrelevant means for transmitting well survey signals E21B47/12; signal transmission systems in general G08C; transmission in general H04B
• CPC Class Codes: H04B 1/10 Means associated with receiver for limiting or suppressing noise or interference

Abstract

A method for reducing interference in a received downhole telemetry signal includes: segmenting a received signal; windowing each signal segment; transforming each windowed signal segment into a complex variable domain to generate a plurality of complex variable domain segments with an in-phase component vector I and a quadrature component vector Q; calculating a real amplitude vector A from the I and the Q vectors; filtering interferers in the amplitude vector A for each complex variable domain segment to generate a filtered amplitude vector Ã; recalculating an amplitude of the amplitude vector A using the filtered amplitude vector à to generate an output amplitude vector Â; scaling the I and the Q vectors by a factor Â/A to generate an output in-phase component vector I′ and an output quadrature component vector Q′; and transforming I′ and Q′ into the time domain to provide an interference-reduced output signal in the time domain.

Claims

1. A method for reducing interference in a received downhole telemetry signal, the method comprising:

receiving a downhole telemetry signal in a time domain with a receiver;

segmenting the received signal into a plurality of signal segments;

windowing each signal segment in the plurality of signal segments to generate a plurality of windowed signal segments;

transforming each windowed signal segment in the plurality of windowed signal segments into a complex variable domain to generate a plurality of complex variable domain segments, each complex variable domain segment having an in-phase component vector I and a quadrature component vector Q;

calculating a real amplitude vector A from the in-phase component vector I and the quadrature component vector Q for each complex variable domain segment;

filtering interferers in the amplitude vector A for each complex variable domain segment to generate a filtered amplitude vector Ã

for each complex variable domain segment;

recalculating an amplitude of the amplitude vector A using the filtered amplitude vector Ã

for each complex variable domain segment to generate an output amplitude vector Â

for each complex variable domain segment;

scaling the in-phase component vector I and the quadrature component vector Q by a factor Â

/A for each complex variable domain segment to generate an output in-phase component vector I′ and

an output quadrature component vector Q′

for each complex variable domain segment; and

transforming I′ and

Q′

for each complex variable domain segment into the time domain to provide an interference-reduced output signal in the time domain;

wherein the segmenting, windowing, transforming each windowed signal segment, calculating a real amplitude vector A, filtering, recalculating, scaling I and Q, and transforming I′ and

Q′

are performed using a processor.

2. The method according to claim 1, wherein each signal segment in the plurality of signal segments overlaps an adjacent signal segment.

3. The method according to claim 2, wherein an amount of overlap is expressed as a percentage of a length N of the signal segment being overlapped.

4. The method according to claim 1, wherein the complex variable domain is a frequency domain.

5. The method according to claim 1, wherein the windowing is performed using a Hamming window.

6. The method according to claim 1, wherein the windowing comprises using the plurality of signal segments as the plurality of windowed signal segments.

7. The method according to claim 1, wherein the transforming each windowed signal segment is performed using a discrete Fourier transform.

8. The method according to claim 1, wherein a length of a signal segment is N, the transformation is performed in blocks having a block length M, and if M is less than N then padding the block with zeros.

9. The method according to claim 1, wherein the filtering interferers in the amplitude vector A comprises a non-linear filtering operation.

10. The method according to claim 9, wherein the non-linear filtering operation comprises using a median filter.

11. The method according to claim 1, wherein the recalculating an amplitude comprises calculating a difference between the amplitude vector A and the filtered vector Ã

and if the difference is greater than a predefined threshold, then using corresponding elements of Ã

as the output amplitude vector Â

.

12. The method according to claim 1, wherein the recalculating an amplitude comprises comparing the amplitude vector A against a predefined threshold vector (t2+1) Ã

where t2 is a configurable threshold.

13. The method according to claim 1, wherein the recalculating an amplitude comprises copying the amplitude vector A and then replacing all values exceeding a threshold value with corresponding values from the filtered amplitude vector Ã

.

14. The method according to claim 1, wherein the transforming I′

and Q′

comprises using an inverse discrete Fourier transform.

15. The method according to claim 1, wherein the transforming I′

and Q′

comprises using an overlap-add method to account for any overlap in adjacent signal segments in the plurality of signal segments.

16. The method according to claim 1, wherein the downhole telemetry signal comprises a mud-pulse telemetry signal.

17. An apparatus for reducing interference in a received downhole telemetry signal, the apparatus comprising:

a receiver configured to receive a downhole telemetry signal in a time domain; and

a processor coupled to the receiver and configured to implement a method comprising;

segmenting the received signal into a plurality of signal segments;

windowing each signal segment in the plurality of signal segments to generate a plurality of windowed signal segments;

transforming each windowed signal segment in the plurality of windowed signal segments into a complex variable domain to generate a plurality of complex variable domain segments, each complex variable domain segment having an in-phase component vector I and a quadrature component vector Q;

calculating a real amplitude vector A from the in-phase component vector I and the quadrature component vector Q for each complex variable domain segment;

filtering interferers in the amplitude vector A for each complex variable domain segment to generate a filtered amplitude vector Ã

for each complex variable domain segment;

recalculating an amplitude of the amplitude vector A using the filtered amplitude vector Ã

for each complex variable domain segment to generate an output amplitude vector Â

for each complex variable domain segment;

scaling the in-phase component vector I and the quadrature component vector Q by a factor Â

/A for each complex variable domain segment to generate an output in-phase component vector I′ and

an output quadrature component vector Q′

for each complex variable domain segment; and

transforming I′ and

Q′

for each complex variable domain segment into the time domain to provide an interference-reduced output signal in the time domain.

18. The apparatus according to claim 17, wherein the downhole telemetry signal comprises a mud-pulse telemetry signal.

19. The apparatus according to claim 18, wherein the receiver is configured to receive a series of pressure pulses in drilling fluid and convert the series of pressure pulses into the mud-pulse telemetry signal, the mud-pulse telemetry signal comprising data obtained from a downhole tool disposed at a drill tubular.

20. A non-transitory computer readable medium comprising computer executable instructions for reducing interference in a received downhole telemetry signal by implementing a method comprising:

segmenting a received downhole telemetry signal in a time domain into a plurality of signal segments;

windowing each signal segment in the plurality of signal segments to generate a plurality of windowed signal segments;

transforming each windowed signal segment in the plurality of windowed signal segments into a complex variable domain to generate a plurality of complex variable domain segments, each complex variable domain segment having an in-phase component vector I and a quadrature component vector Q;

calculating a real amplitude vector A from the in-phase component vector I and the quadrature component vector Q for each complex variable domain segment;

filtering interferers in the amplitude vector A for each complex variable domain segment to generate a filtered amplitude vector Ã

for each complex variable domain segment;

recalculating an amplitude of the amplitude vector A using the filtered amplitude vector Ã

for each complex variable domain segment to generate an output amplitude vector Â

for each complex variable domain segment;

scaling the in-phase component vector I and the quadrature component vector Q by a factor Â

/A for each complex variable domain segment to generate an output in-phase component vector I′ and

an output quadrature component vector Q′

for each complex variable domain segment; and

transforming I′ and

Q′

for each complex variable domain segment into the time domain to provide an interference-reduced output signal in the time domain;

wherein the segmenting, windowing, transforming each windowed signal segment, calculating a real amplitude vector A, filtering, recalculating, scaling I and Q, and transforming I′ and

Q′

are performed using a processor.