초록 ▼

A method of signal processing includes providing at least a first pressure sensor and a second pressure sensor spaced in a drilling system and using an algorithm to separate the downwardly propagating waves from the upwardly propagating waves. In one or more examples, an algorithm may include determ

A method of signal processing includes providing at least a first pressure sensor and a second pressure sensor spaced in a drilling system and using an algorithm to separate the downwardly propagating waves from the upwardly propagating waves. In one or more examples, an algorithm may include determining a velocity of pressure signals in a wellbore, time-shifting and stacking pressure signals from at least the first pressure sensor and the second pressure sensor to determine a downwardly propagating noise signal, and subtracting the downwardly propagating noise signal from at least the signal from the first pressure sensor.

대표청구항 ▼

1. A method for wellbore communications, comprising: obtaining a first corrected pressure signal and a downwardly propagating noise signal from at least a first pressure sensor;computing a cross-correlation function between the first corrected pressure signal and the downwardly propagating noise sig

1. A method for wellbore communications, comprising: obtaining a first corrected pressure signal and a downwardly propagating noise signal from at least a first pressure sensor;computing a cross-correlation function between the first corrected pressure signal and the downwardly propagating noise signal for at least the first pressure sensor;computing the standard deviation of the downwardly propagating noise signal;computing a reflection coefficient for the downwardly propagating noise signal; from the standard deviation of the downwardly propagating noise signal;computing the reflected, upwardly propagating noise signal from the reflection coefficient for the downwardly propagating noise signal; andsubtracting the reflected, upwardly propagating noise signal from the first corrected pressure signal. 2. The method of claim 1, wherein: the cross-correlation function comprises: C3⁢D⁡(d)=∑k=0m-1⁢{[R3⁡(tk)-R3_]·[ND⁡(tj)-ND_]};computing the reflection coefficient for the downwardly propagating noise signal comprises averaging the following equation over a plurality of measurements; A·ⅇⅈϕ=〈C3⁢D⁡(d)〉(m-1)⁢〈σN2〉;subtracting the reflected, upwardly propagating noise signal is performed using the following equation: {tilde over (R)}3(t)=R3(t)−Aeiφ·ND(t·Tc−Ta); andwherein C3D(d) represents the cross-correlation function, R3(tk) represents the first corrected pressure signal at time tk, R3 represents an average corrected pressure signal, ND(tj) represents the downwardly propagating noise signal at time tj, ND represents an average downwardly propagating noise signal, Aeiφ represents the reflection coefficient for the downwardly noise signal, σN represents the standard deviation of the downwardly propagating noise signal, (•) represents an average over many measurements, Aeiφ·ND(t+Tc−Ta) represents the reflected, upwardly propagating noise signal; R3(t) represents the first corrected pressure signal, and {tilde over (R)}3(t) represents a twice corrected pressure signal. 3. The method of claim 1, wherein computing the standard deviation of the downwardly propagating noise signal is performed in a time window corresponding to a maximum value for the cross-correlation function. 4. The method of claim 1, wherein subtracting the reflected, upwardly propagating noise signal from the first corrected pressure signal yields a first twice corrected pressure signal, and further comprising: obtaining a second corrected pressure signal and a downwardly propagating noise signal from a second pressure sensor;computing a cross-correlation function between the second corrected pressure signal and the downwardly propagating noise signal for the second pressure sensor;computing the standard deviation of the downwardly propagating noise signal from the second pressure sensor;computing a reflection coefficient for a mud pump noise at the second pressure sensor;subtracting an upwardly propagating noise signal at the second pressure sensor from the second corrected pressure signal to obtain a second twice corrected pressure signal; andtime-shifting and stacking the first twice corrected pressure signal and the second twice corrected pressure signal.