Wellbore Telemetry and Noise Cancelation Systems and Methods for the Same

Abstract

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.

What is claimed is: 
     
         1 . A method of signal processing, comprising:
 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.   
     
     
         2 . The method of  claim 1 , wherein using an algorithm to separate the downwardly propagating waves from the upwardly propagating waves comprises:
 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.   
     
     
         3 . The method of  claim 2 , further comprising:
 subtracting the downwardly propagating noise signal from the signal from at least the second pressure sensor; and   time-shifting and stacking at least the signal from the first pressure sensor and the signal from the second pressure sensor to obtain the upwardly propagating data signal.   
     
     
         4 . The method of  claim 3 , wherein
 providing at least a first pressure sensor and a second pressure sensor comprises providing the first pressure sensor, the second pressure sensor, and a third pressure sensor, and wherein:   time-shifting and stacking at least the signal from the first pressure sensor and the signal from the second pressure sensor to determine a downwardly propagating noise signal comprises time-shifting and stacking the signal from the first, second, and third pressure sensors; and wherein   subtracting the downwardly propagating noise signal from at least the signal from the first pressure sensor comprises subtracting the downwardly propagating noise signal from the signals from the first, second, and third pressure sensors.   
     
     
         5 . The method of  claim 4 , wherein: time-shifting and stacking the signals from the first, second, and third pressure sensors to determine the downwardly propagating noise signal is performed using the following equation:
     N   D ( t )={ S 1( t )+ S 2( t +( Z 2− Z 1)/ V )+ S 3( t +( Z 3− Z 1)/ V )}/3;
   and wherein subtracting the downwardly propagating noise signal from the signals from the first, second, and third pressure sensors is performed using the following equations:
     R 1( t )= S 1( t )− N   D ( t ),
 
     R 2( t )= S 2( t )− N   D ( t +( Z 2− Z 1)/ V ),
 
     R 3( t )= S 3( t )− N   D ( t +( Z 3− Z 1)/ V ).
 
   
     
     
         6 . The method of  claim 2 , further comprising transmitting pressure signals from at least the first and second pressure sensor to a surface location. 
     
     
         7 . The method of  claim 6 , wherein the pressure signals are transmitted through one of a wired drill pipe, an electromagnetic telemetry tool, a wireline cable, a fiber-optic cable, and a wireless communication device. 
     
     
         8 . The method of  claim 3 , wherein the upwardly propagating data signal comprises an MWD signal. 
     
     
         9 . The method of  claim 2 , wherein determining the velocity of signals in the wellbore fluid comprises:
 determining at least one cross-correlation function between the signals from at least the first pressure sensor and the second pressure sensor for downwardly propagating waves;   determining a maximum value for the at least one cross-correlation function; and   determining the velocity of the signals in the wellbore fluid based on a maximum value of the at least one cross-correlation function.   
     
     
         10 . The method of  claim 9 , wherein: the cross-correlation function comprises:
     C 12( d )=Σ k=0   m-1   {[S 1( tk )−    S 1 ]·[ S 2( tk )−    S 2 ]}; and
   determining the velocity of signals in the wellbore fluid comprises solving for V, using the maximum value of the cross-correlation function and the following equation:
     d·Δ·t =( Z   2   −Z   1 )/ V.    
   
     
     
         11 . The method of  claim 9 , wherein determining at least one cross-correlation function between at least the first pressure sensor and the second pressure sensor for downwardly propagating waves comprises: determining a cross-correlation between the signals from the first pressure sensor and the second pressure sensor; determining a cross-correlation between the signals from the first pressure sensor and a third pressure sensor; and determining a cross-correlation between the signals from the second pressure sensor and the third pressure sensor. 
     
     
         12 . The method of  claim 1 , wherein providing at least a first pressure sensor and a second pressure sensor spaced in a drilling system comprises: positioning a wireline device within the drilling system, wherein the wireline device includes the at least a first pressure sensor and a second pressure sensor. 
     
     
         13 . The method of  claim 1 , wherein providing a first pressure sensor and a second pressure sensor spaced in a drilling system comprises: positioning a fiber-optic device within the drilling system, wherein the fiber-optic device includes the at least a first pressure sensor and a second pressure sensor. 
     
     
         14 . The method of  claim 1 , wherein providing at least a first pressure sensor and a second pressure sensor spaced in a drilling system comprises: positioning the first pressure sensor, the second pressure sensor, and a third pressure sensor within one selected from a drill string, and a casing. 
     
     
         15 . The method of  claim 1 , wherein using an algorithm to separate the downwardly propagating waves from the upwardly propagating waves comprises using f-k processing techniques. 
     
     
         16 . The method of  claim 15 , wherein using f-k processing techniques comprises applying a fourier transform of signals from at least the first pressure sensor and the second pressure sensor from spatial and temporal dimensions into data in frequency and wavenumber dimensions. 
     
     
         17 . The method of  claim 16 , wherein the data in frequency and wavenumber dimensions are multiplied by factors to produce a reduced data set where at least one of an amplitude and a frequency of downwardly propagating waves associated with noise is minimized. 
     
     
         18 . The method of  claim 17 , further comprising applying an inverse fourier transform on the reduced data set to transform the data set back to the spatial and temporal dimensions. 
     
     
         19 . The method of  claim 1 , wherein the downwardly propagating waves comprise noise and the upwardly propagating waves comprise a data signal. 
     
     
         20 . The method of  claim 1 , wherein the downwardly propagating waves comprise a data signal and the upwardly propagating signal comprises one of noise and a second data signal.