MODULATION SCHEME FOR HIGH SPEED MUD PULSE TELEMETRY WITH REDUCED POWER REQUIREMENTS

• US 20160245078A1
• Filed: 02/19/2015
• Published: 08/25/2016
• Est. Priority Date: 02/19/2015
• Status: Abandoned Application

• Current Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Original Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Inventors: Mahmoud, Sameh Amr Hassanein, Gatzen, Matthias, Bruns, Jens Uwe, Emmerich, Wojciech
• Application Number:
  US14/625,813
• Publication Number:
  US 20160245078A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: E21B 47/18 through the well fluid , e.g. mud pressure pulse telemetry
• CPC Class Codes: E21B 47/20 by modulation of mud waves, e.g. by continuous modulation

Abstract

A method for transmitting data from a downhole location to a location at the surface of the earth includes: receiving data using a modulator disposed at the downhole location on a drill tubular in a borehole penetrating the earth and modulating the data using offset quadrature phase shift keying (OQPSK) and smooth transitions between phase shifts to produce a series of two-bit symbols having smooth transitions in transition intervals between phase shifts of both in-phase and quadrature-phase components of the OQPSK modulated data. The method further includes transmitting the series of two-bit symbols as an acoustic signal in drilling fluid disposed in the borehole using a mud-pulser, receiving the acoustic signal using a receiver disposed uphole from the downhole location; and demodulating the acoustic signal using a demodulator coupled to the receiver to provide demodulated data.

Claims

1. A method for transmitting data from a downhole location to a location at the surface of the earth, the method comprising:

receiving data using a modulator disposed at the downhole location on a drill tubular in a borehole penetrating the earth;

modulating, using the modulator, the data using offset quadrature phase shift keying (OQPSK) and smooth transitions between phase shifts to produce a series of two-bit symbols having smooth transitions in transition intervals between phase shifts of both in-phase and quadrature-phase components of the OQPSK modulated data;

transmitting the series of two-bit symbols as an acoustic signal in drilling fluid disposed in the borehole using a mud-pulser;

receiving the acoustic signal using a receiver disposed uphole from the downhole location; and

demodulating the acoustic signal using a demodulator coupled to the receiver to provide demodulated data.

2. The method according to claim 1, wherein one or more of the smooth transitions is characterized by a continuous first derivative of amplitude with respect to time.

3. The method according to claim 1, wherein a smooth transition comprises a change of instantaneous frequency of the acoustic signal.

4. The method according to claim 1, wherein each of the transition intervals are of the same duration.

5. The method according to claim 1, wherein at least two transition intervals have different time durations.

6. The method according to claim 1, further comprising applying forward error correction encoding before modulating the data.

7. The method according to claim 6, wherein the forward error correction encoding comprises turbo coding.

8. The method according to claim 6, further comprising applying forward error correction decoding to the demodulated data uphole of the downhole location.

9. The method according to claim 1, further comprising storing the demodulated data in memory or a storage medium.

10. The method according to claim 1, further comprising sensing a downhole property using a downhole sensor and transmitting sensed data to the modulator.

11. The method according to claim 10, wherein the downhole sensor is configured to sense at least one of temperature, pressure, radiation, optical reflectivity, optical transmissivity, acoustic energy, electrical current, electrical voltage and electromagnetic waves.

12. The method according to claim 10, further comprising generating a two-dimensional image representation of the sensed data before transmitting the sensed data to the modulator.

13. The method according to claim 10, further comprising extracting a sample of formation fluid using an extendable probe, sensing a property of the formation fluid using the downhole sensor to provide sensed formation fluid data, and transmitting the sensed formation fluid data to the modulator.

14. An apparatus for transmitting data from a downhole location on a drill tubular to a location at the surface of the earth, the apparatus comprising:

a drill tubular disposed in a borehole penetrating the earth and configured to convey drilling fluid;

a modulator configured to receive data from the downhole location and to modulate the data using offset quadrature phase shift keying (OQPSK) and smooth transitions between phase shifts to produce a series of two-bit symbols having a smooth transitions in a transition intervals between phase shifts of both in-phase and quadrature-phase components of the OQPSK modulated data;

a mud-pulser configured to transmit the series of two-bit symbols as an acoustic signal in drilling fluid disposed in the borehole;

a receiver disposed uphole from the downhole location and configured to receive the acoustic signal; and

a demodulator coupled to the receiver and configured to demodulate the acoustic signal received by the receiver to provide demodulated data.

15. The apparatus according to claim 14, wherein the mud-pulser comprises a plunger configured to interface with the drilling fluid to transmit the acoustic signal.

16. The apparatus according to claim 14, wherein the mud-pulser comprises a rotating or oscillating disc configured to interface with the drilling fluid to transmit the acoustic signal.

17. The apparatus according to claim 14, further comprising a signal receiving device comprising one of a display or printer configured to display the demodulated data to a user.

18. The apparatus according to claim 14, further comprising a signal receiving device comprising one of a storage medium or memory configured to store the demodulated data.

19. The apparatus according to claim 14, further comprising an encoder configured to apply a forward error correcting code before the data is modulated by the modulator.

20. The apparatus according to claim 14, further comprising a sensor disposed on the drill tubular and configured to sense a downhole property and transmit sensed property data to the modulator.

21. The apparatus according to claim 20, wherein the sensed property comprises at least one of temperature, pressure, radiation, optical reflectivity, optical transmissivity, acoustic energy, electrical current, electrical voltage and electromagnetic waves.

22. The apparatus according to claim 21, further comprising a formation fluid tester configured to extract and analyze a sample of formation fluid and to transmit formation fluid property data to the modulator.