# US 2013/0154845 A1 · Mud Pulse Telemetry Noise Reduction Method

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- Number: US 2013/0154845 A1
- Document ID: US20130154845A1
- Status: Published application
- Kind: A1
- Application number: 13/819,165
- Filed: 2011-08-26
- Published: 2013-06-20
- Earliest claimed: 2010-08-26
- Assignees: Schlumberger Technology Corporation
- Inventors: Andrew G. Brooks
- Web page: https://patentgrep.com/patent/US20130154845A1

## CPC

- G01V 3/18: specially adapted for well-logging
- E21B 47/18: through the well fluid {, e.g. mud pressure pulse telemetry}
- 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)}
- G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02)
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS

## Abstract

A method for reducing noise in downhole fluid communications includes processing first and second received signals in combination with a strobe signal from an active pump to obtain pump signatures at first and second spaced measurement locations. The pump signatures are used to compute a transfer function of the fluid channel between the two measurement locations. The transfer function may then be used to estimate the telemetry signal traveling in the uphole direction.

## Claims

### Claim 1

A method for communicating a signal through a fluid in a borehole between a first downhole location and a second uphole location, the method comprising:
(a) receiving signals in the fluid at at least first and second spaced uphole positions, the received signals including at least a telemetry signal, a reflected telemetry signal, and a pump noise signal;
(b) receiving a strobe signal from an active pump, the pump being in fluid communication with the first and second positions;
(c) causing a processor to process the signals received in (a) and the strobe signal received in (b) to obtain pump signatures and clean signals at each of the first and second positions, the pump signatures including the pump noise signal and the clean signals including the telemetry signal and the reflected telemetry signal;
(d) causing the processor to compute a transfer function between the first and second positions from the pump signatures obtained in (c); and
(e) causing the processor to remove the reflected telemetry signal from at least one of the clean signals via processing the transfer function computed in (d) and the clean signals obtained in (c) so as to obtain the telemetry signal.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
(f) causing the processor to decode the telemetry signal.

### Claim 3 (depends on 2)

The method of claim 2, wherein said decoding in (f) utilizes at least one of pulse position coding, amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK).

### Claim 4 (depends on 1)

The method of claim 1, wherein the signals received in (a) comprise fluid pressure signals.

### Claim 5 (depends on 1)

The method of claim 1, wherein a plurality of strobe signals are received in (b) from a corresponding plurality of active pumps.

### Claim 6 (depends on 1)

The method of claim 1, wherein said processing in (c) comprises a stacking algorithm.

### Claim 7 (depends on 1)

The method of claim 1, wherein the transfer function is computed in (d) according to the following mathematical equation:
H
=
D


F


T

(
pump


2
)
D


F


T

(
pump


1
)
wherein H represents the transfer function, pump1 and pump2 represent the pump signatures obtained in (c) at the first and second positions, and DFT is the discrete Fourier transform operation.

### Claim 8 (depends on 1)

The method of claim 1, wherein the telemetry signal is obtained in (e) in the frequency domain according to the following mathematical equation:
D


T


F


T

(
S
)
=
D


T


F


T

(
T
2
)
-
H
·
D


T


F


T

(
T
1
)
1
-
H
·
H
wherein S represents the telemetry signal, T1 and T2 represent the clean signals obtained in (c), H represents the transfer function computed in (d), and DTFT represents the discrete time Fourier transform operation.

### Claim 9 (depends on 1)

The method of claim 1, wherein the telemetry signal is obtained in (e) in the time domain according to the following mathematical equation:
S=T2*F1−T1*F2
wherein S represents the telemetry signal, T1 and T2 represent the clean signals obtained in (c), * represents the convolution operator, and F1 and F2 are related to the transfer function H as follows:
F
1
=
I


D


F


T

(
1
1
-
H
·
H
)
;
F
2
=
I


D


F


T

(
H
1
-
H
·
H
)
;
wherein IDFT represents the inverse discrete Fourier transform operation.

### Claim 10

A system for communicating a signal through a fluid in a borehole between a first downhole location and a second uphole location, the system comprising:
a transmission device deployed at the downhole location;
first and second sensors deployed at first and second spaced apart positions at the uphole location; and
a controller configured to: (i) receiving signals from the first and second sensors, the received signals including at least a telemetry signal, a reflected telemetry signal, and a pump noise signal; (ii) receive a strobe signal from an active pump, the pump being in fluid communication with the first and second positions; (iii) process the received signals and the strobe signal to obtain pump signatures and clean signals at each of the first and second positions, the pump signatures including the pump noise signal and the clean signals including the telemetry signal and the reflected telemetry signal; (iv) compute a transfer function between the first and second positions from the pump signatures; and (v) remove the reflected telemetry signal from at least one of the clean signals via processing the transfer function and the clean signals so as to obtain the telemetry signal.

### Claim 11 (depends on 10)

The method of claim 10, wherein the controller is further configured to (vi) decode the telemetry signal.

### Claim 12 (depends on 11)

The method of claim 11, wherein said decoding in (vi) utilizes at least one of pulse position coding, amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK).

### Claim 13 (depends on 10)

The method of claim 10, wherein the transmission device comprises an electromechanical pulser and a mud siren.

### Claim 14 (depends on 10)

The method of claim 10, wherein the first and second sensors comprise first and second transducers.

### Claim 15 (depends on 10)

The method of claim 10, wherein the controller is configured to receive a plurality of strobe signals from a corresponding plurality of active pumps.

### Claim 16 (depends on 10)

The method of claim 10, wherein the controller is configured to execute a stacking algorithm in (iii).

### Claim 17 (depends on 10)

The method of claim 10, wherein the controller is configured to compute the transfer function in (iv) according to the following mathematical equation:
H
=
D


F


T

(
pump


2
)
D


F


T

(
pump


1
)
wherein H represents the transfer function, pump1 and pump2 represent the pump signatures obtained in (iii) at the first and second positions, and DFT is the discrete Fourier transform operation.

### Claim 18 (depends on 10)

The method of claim 10, wherein the controller is configured to obtain the telemetry signal in the frequency domain in (v) according to the following mathematical equation:
D


T


F


T

(
S
)
=
D


T


F


T

(
T
2
)
-
H
·
D


T


F


T

(
T
1
)
1
-
H
·
H
wherein S represents the telemetry signal, T1 and T2 represent the clean signals obtained in (iii), H represents the transfer function computed in (iv), and DTFT represents the discrete time Fourier transform operation.

### Claim 19 (depends on 10)

The method of claim 10, wherein the controller is configured to obtain the telemetry signal in the time domain in (v) according to the following mathematical equation:
S=T2*F1−T1*F2
wherein S represents the telemetry signal, T1 and T2 represent the clean signals obtained in (iii), * represents the convolution operator, and F1 and F2 are related to the transfer function H as follows:
F
1
=
I


D


F


T

(
1
1
-
H
·
H
)
;
F
2
=
I


D


F


T

(
H
1
-
H
·
H
)
;
wherein IDFT represents the inverse discrete Fourier transform operation.