NAME

     vmod - Velocity Perturbation Model Generation

SYNOPSIS

     vmod [-Ootap] [-Ccardfile] [-V]

DESCRIPTION

     vmod generates a V(z) function suite to be used for prestack
     depth  migration  in  program  cubevz. The function input on
     cards is converted to time vs.  interval  velocity,  pertur-
     bated  as directed, converted to depth vs. interval velocity
     and output.

  Command line arguments
     -O otap
          Enter the name of the output V(z) suite  dataset  after
          typing -O.

     -V   Enter -V for a verbose printout.

     -Ccardfile
          If the parameters are in a separate  card  file,  enter
          the  name  of that file after typing -C. Alternatively,
          by using the  catpat  command  a  script  file  can  be
          created  which  will contain the command line arguments
          and the other necessary parameters for executing  vmod.
          The script file may then be edited to enter the correct
          values. The script  file  may  be  executed  using  the
          "startjob" command.

SCRIPT FILES FORMAT:

     vmod -Ootap \
     -vmod.crd"\
     VEL MODEL   # FUNCTS    VBLOCK
                    nfunc    vblock
     PERTURBNO      BEG #     END #
                      beg       dnD
     INPUT        INT/RMS   TIM/DEP
                   intrms    timdeP
     OUTPUT      MAXDEPTH    DELTAZ
                     zmax        dz
     VELOCITIES TIME/DPTH      VMIN      VMAX      VMID  RATIOMIN  RATIOMAX
     VELOCITIES  timedpth      vmin      vmax      vmid  ratiomin  ratiomax
     VELOCITIES  timedpth      vmin      vmax      vmid  ratiomin  ratiomax
     "

     # FUNCTSnfunc
          Number of V(z) functions with which to migrate.

     VBLOCKvblock
          Allowable error  (in  velocity  units).   The  velocity
          functions will be blocked into constant velocity layers
          such that the  error  in  the  velocity  values  is  no
          greater  than  VBLOCK.   Velocity  blocking is used for
          greater efficiency in the migrations.

     BEG #beg
          Beginning perturbation number. (default 1) In order  to
          extend  velocity  model  beyond  the minimum or maximum
          velocities  the  beginning  and   ending   perturbation
          numbers  may be used.  This will also change the number
          of functions.  If both BEG # and END # are 0 they  will
          default.

     END #end
          Ending perturbation number. (default = # FUNCTS)

     INT/RMSintrms
          1 -- input velocities are in interval velocity
          2 -- input velocities are in rms velocity
               velocities are in ft/sec or m/sec

     TIM/DEPtimdep
          1 -- input velocities are a function of time
          2 -- input velocities are a function of depth
               velocities are in ft/sec or m/sec

     MAXDEPTH zmax
          Maximum depth (ft or meters) of output velocity pertur-
          bation model

Depth increment (ft or meters) of  output  velocity  perturbation
model


     TIME/DPTH timedpth
          Size of the  velocity fairway.
             If input velocities are in time (TIM/DEP=1),
                this fairway is in ms.
             If input velocities are in depth (TIM/DEP=2),
                this fairway is in ft or meters.

     VMIN vmin
          Velocity of the first velocity function  in  ft/sec  or
          m/sec.   (blank  values  and  intermediate  values  are
          interpolated)

     VMAX vmzx
          Velocity of the last velocity function (velocity  func-
          tion number = nfunc) in ft/sec or m/sec.  (blank values
          and intermediate values are interpolated)


     VMID vmid
          Velocity of the middle function.

     RATIOMIN ratiomin
          Ratio of minimum velocity to middle velocity function.

     RATIOMAX ratiomax
          Ratio of maximum velocity to middle velocity function.

EXAMPLES OF FAIRWAY CALCULATIONS

     The velocity functions can be  input  in  several  different
     ways.   If any of the VMID column is filled, in this will be
     used as the middle velocity function.  The boundaries of the
     velocity  fairway  can  be  defined  using the VMIN and VMAX
     columns or by using the RATIOMIN and RATIOMAX  columns,  but
     not both.

     If values are left blank they will be filled in by  linearly
     interpolating with respect to TIME/DPTH.

     Method 1: fairway defined in terms of a minimum and maximum function
     VELOCITIES TIME/DPTH      VMIN      VMAX      VMID  RATIOMIN  RATIOMAX
     VELOCITIES     1328.      5400      6600     6000.
     VELOCITIES     2531.                         6319.
     VELOCITIES     3082.      5720      7800     6500.
     #...|....1....|....2....|....3....|....4....|....5....|....6....|....7

     Method 2: fairway defined in terms of ratios of VMID
               ( VMIN = VMID*RATIOMIN )
               ( VMAX = VMAX*RATIOMAX )
     VELOCITIES TIME/DPTH      VMIN      VMAX      VMID  RATIOMIN  RATIOMAX
     VELOCITIES     1328.                         6000.       .90      1.10
     VELOCITIES     2531.                         6319.
     VELOCITIES     3082.                         6500.       .88      1.20
     #...|....1....|....2....|....3....|....4....|....5....|....6....|....7

SEE ALSO

     cubevz, fsi, cubevz.flow, apkr.flow, apkr, p2iv

BUGS

     None known.

AUTHOR

     Curtis Kruse

COPYRIGHT

     copyright 2001, Amoco Production Company
               All Rights Reserved
          an affiliate of BP America Inc.