Acoustic telemetry systems and methods with surface noise cancellation
Acoustic telemetry systems and methods with surface noise cancellation. One illustrative embodiment may include an acoustic telemetry system comprising a transmitter configured to generate an acoustic information signal that propagates along a drillstring, and a receiver configured to detect an acoustic receive signal from the drillstring and a noise signal from a surface environment. The receiver operates on the acoustic receive signal and the noise signal to produce a modified signal indicative of the acoustic information signal and having a reduced noise content relative to the acoustic receive signal.
1. An acoustic telemetry system, comprising:
a transmitter to generate an acoustic information signal that propagates along a drillstring; and
a receiver to detect an acoustic receive signal from the drillstring, to detect a noise signal at a surface location other than the kelly, and to operate on the acoustic receive signal and the noise signal to produce a modified signal indicative of the acoustic information signal and having a reduced noise content relative to the acoustic receive signal.
2. The system of claim 1 , wherein the receiver comprises:
a filter configured to operate on the noise signal to produce an estimated noise component signal; and
a summing element to subtract the estimated noise component signal from the acoustic receive signal.
3. The system of claim 2 , wherein the filter is adaptive and operable to minimize the noise content of the modified signal.
4. The system of claim 1 , wherein the receiver detects multiple noise signals from the surface environment.
5. The system of claim 4 , wherein the receiver combines the multiple noise signals with the acoustic receive signal so as to provide the modified signal having a reduced noise content.
6. The system of claim 1 , further comprising:
at least one noise sensor that detects said noise signal; and
at least one signal sensor that detects said acoustic receive signal.
7. The system of claim 6 , wherein the signal sensor comprises an accelerometer.
8. The system of claim 6 , wherein the at least one noise sensor comprises one of a sensor set consisting of an accelerometer, a geophone, a microphone, and an antenna.
9. The system of claim 6 , wherein the at least one noise sensor is coupled to a drilling rig.
10. The system of claim 6 , wherein the at least one noise sensor is acoustically coupled to equipment positioned near a drilling rig.
11. The system of claim 6 , wherein the at least one noise sensor is embedded in the ground near a drilling rig.
12. The system of claim 6 , wherein the at least one noise sensor is wirelessly coupled to the receiver to provide said noise signal.
13. The system of claim 6 , wherein the at least one noise sensor comprises a microphone and the at least one signal sensor comprises an accelerometer.
14. An acoustic telemetry system, comprising:
a transmitter to generate an acoustic information signal that propagates along a drillstring; and
a receiver to detect an acoustic receive signal from the drillstring, to detect a noise signal from a surface environment, and to operate on the acoustic receive signal and the noise signal to produce a modified signal indicative of the acoustic information signal and having a reduced noise content relative to the acoustic receive signal,
wherein the receiver detects multiple noise signals from the surface environment, and wherein the receiver comprises:
multiple filters, each operating on a respective noise signal to produce an estimated noise component signal; and
a summing element to subtract the estimated noise component signals from the acoustic receive signal.
15. The system of claim 14 , wherein each of the multiple filters is adaptive.
16. A downhole telemetry method that comprises:
generating a first information-carrying acoustic signal that propagates along a drillstring;
detecting a second information-carrying acoustic signal that correlates to the first information-carrying signal;
receiving a surface noise signal from the drilling site environment with a microphone;
combining the surface noise signal with the second information-carrying signal to produce a third information-carrying signal having a reduced noise content; and
demodulating the third information-carrying signal.
17. The method of claim 16 , wherein said combining comprises:
adaptively filtering the surface noise signal to obtain a noise estimate signal; and
subtracting the estimate signal from the second information-carrying acoustic signal to obtain the third information-carrying signal.
18. The method of claim 16 , further comprising:
receiving multiple noise signals from separate sources, wherein the received multiple noise signals includes said surface noise signal; and
operating on the multiple noise signals to obtain a noise estimate signal, wherein said combining the surface noise signal with the second information-carrying signal comprises subtracting the noise estimate signal from the second information-carrying signal.
19. The method of claim 18 , wherein said operating comprises:
filtering each of the multiple noise signals to obtain a respective noise estimate component; and
adding the noise estimate components to obtain the noise estimate signal.
20. The method of claim 16 , wherein said receiving a surface noise signal further comprises detecting vibration of a drilling rig.
21. The method of claim 16 , wherein said receiving further comprises measuring environmental noise with a geophone inserted into the ground near a drilling rig.