Patent ID: 11880011
Assignee: UNIVERSITY OF HOUSTON SYSTEM
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. A method for processing seismic data to remove interference from surface waves prior to analysis of the seismic data in connection with seismic exploration of subsurface energy sources, comprising:
obtaining and recording input multi-channel seismic data from a plurality of receivers located near a subsurface feature, wherein the input multi-channel seismic data comprises a plurality of recorded seismic traces at a plurality of locations near the receivers;
generating estimated surface wave phase velocities from the input multi-channel seismic data using nonlinear signal comparison (NLSC), wherein the step of generating estimated surface wave phase velocities comprises using the following equation:, S
     NLSC
     ij
    
    (
    
     ω
     ,
     
      
       V
       ph
      
      ;
      σ
     
    
    )
   
   =
   
    
     
      
       S
       NL
       ij
      
      (
      
       ω
       ,
       
        
         V
         ph
        
        (
        ω
        )
       
      
      )
     
     -
     
      
       S
       π
      
      (
      ω
      )
     
    
    
     1
     -
     
      
       S
       π
      
      (
      ω
      )
     
    
   
  
  ,
 

wherein ω is frequency,
Vph(ω) is phase-velocity,
SNLSCij is a normalized dispersion map using ith and jth traces,
σ is a nonnegative parameter to control resolution,
SNLij is an unnormalized dispersion map represented by:, S
     NL
     ij
    
    (
    
     ω
     ,
     
      V
      
       p
       ⁢
       h
      
     
    
    )
   
   =
   
    
     1
     T
    
    ⁢
    
     
      
       ∫
       T
      
      0
     
     
      
       exp
       (
       
        -
        
         
          
           [
           
            
             
              
               d
               _
              
              i
             
             (
             
              t
              ;
              ω
             
             )
            
            -
            
             
              
               d
               _
              
              j
             
             (
             
              
               t
               +
               
                
                 x
                 ij
                
                
                 V
                 ph
                
               
              
              ;
              ω
             
             )
            
           
           ]
          
          2
         
         
          4
          ⁢
          
           ω
           2
          
          ⁢
          
           π
           
            -
            2
           
          
          ⁢
          
           σ
           2
          
         
        
       
       )
      
      ⁢
      dt
     
    
   
  
  ,
 

wherein T is the length of the measured time window,
di and dj are recorded seismic traces normalized by variance and represented as:, d
      _
     
     i
    
    (
    
     t
     ;
     ω
    
    )
   
   -
   
    
     σ
     i
     
      -
      1
     
    
    ⁢
    
     
      d
      i
     
     (
     
      t
      ;
      ω
     
     )
    
   
  
  ,
  
   
    
     
      d
      _
     
     j
    
    (
    
     
      t
      +
      
       
        x
        ij
       
       
        V
        ph
       
      
     
     ;
     ω
    
    )
   
   =
   
    
     σ
     j
     
      -
      1
     
    
    ⁢
    
     
      d
      j
     
     (
     
      
       t
       +
       
        
         x
         ij
        
        
         V
         ph
        
       
      
      ;
      ω
     
     )
    
   
  
  ,
 

wherein σi and σj are variances defined as:, σ
    t
    2
   
   =
   
    
     ∫
     0
     T
    
    
     
      
       d
       i
       2
      
      (
      
       t
       ;
       ω
      
      )
     
     ⁢
     dt
    
   
  
  ,
  
   
    σ
    j
    2
   
   =
   
    
     ∫
     0
     T
    
    
     
      
       d
       j
       2
      
      (
      
       
        t
        +
        
         
          x
          ij
         
         
          V
          ph
         
        
       
       ;
       ω
      
      )
     
     ⁢
     dt
    
   
  
  ,
 

 and
Sπ is a reference value for normalization represented by:

Sπ(ω)=I0(b)e−b 

wherein, b
  =
  
   
    π
    2
   
   
    
     σ
     2
    
    ⁢
    
     ω
     2
    
    ⁢
    T
   
  
 

 and I0 is a modified Bessel function of zero-th order;
generating predicted surface waves for each receiver by using the estimated surface wave phase velocities and performing a phase shift and local stacking analysis for seismic traces at locations near each receiver;
subtracting the predicted surface waves from the input multi-channel seismic data to generate seismic data lacking interference from surface waves; and
analyzing the seismic data lacking interference from surface waves to provide information about the subsurface feature, wherein the subsurface feature is an energy source.