Velocity Analysis.docx

Velocity Analysis 1. Flow 05. Velocity AnalysisEditing flow add : supergather formation, bandpass filter, automatic gain control, velocity analysis precompute, disk data output, velocity analysis, volume viewer/editor. 2. MB3 (aktif) pada supergather formation, bandpass filter, automatic gain control, velocity analysis precompute, disk data output, velocity analysis, volume viewer/editor.  MB2 Supergather information  select dataset : pre_prop, maximum CDP fold : 21, minimum center CDP number : 10, maximum center CDP number : 45, CDP increment : 5, CDP to combine : 3.  MB2 Banpass filter  Ormbsy filter frequency values : 7-23-54-75.  MB2 Automatic gain controlAGC operator length : 600.  MB2 Velocity analysis precompute  Number of CDPs to sum into gather : 5, absolute offset of first bin center : 50, bin zise for vertically summing offset : 100, number of stack velocity function : 11, velocity variation at time 0 : 1500, velocity variation at maximum time : 7000, get guide function table name : No, pada guide minimum value isi 1500 dan guide maximum time value 7000 kemudian akan muncul table.

Gambar 3.48 Velocity analysis precompute  MB2 Disk data output  Output dataset filename : velocity Anyal  Execute.

Gambar 3.49 velocity analysis 3. MB3 (non aktif) supergather formation, bandpass filter, AGC, velocity analysis precompute.  MB2 Velocity analysis  table to store velocity picks : velan1, set semblance scaling and autosnap parameters : No, pada get guide function from an existing parameter table pilih No, pada guide minimum value : 1500, guide maximum time value : 7000.

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MB2 disk data output pada output dataset filename : velocity Anyal

 MB2 Volume viewer/editor  source of surface coordinate limits : seismic data, source of depth coordinate limits : seismic data, select input volume : velan1, display poststack seismic data : No

Gambar 3.50 volume viewer/editor  Execute, Akan muncul gambar seperti di bawah ini:

Gambar 3.51 Picking velocity analysis  Picking daerah yang berwarna merah,  Filesave picks. 

Lakukan Picking Velocity dari channel pertama hingga channel terakhir.

 Fileexitsave before exityes.

NMO & Stack 1. Flow  06. NMO Stack  Editing Flow Add : disk data input, normal moveout correction, CDP/ensemble stack, disk data output, add flow comment, disk data input, trace display. 2. MB3 (aktif) pada disk data input, normal moveout correction, disk data output, CDP/ensemble stack, add flow comment, MB3 (nonaktif) pada disk data input, trace display.  MB2 Disk data inputselect dataset : pre_prop  MB2 Normal moveout correction  get velocities from the database : No.  MB2 Disk data outputoutput dataset filename : NMO&Stack  Execute.  MB3 (nonaktif) pada disk data input, normal moveout correction, disk data output, CDP/ensemble stack, add flow comment, MB3 (aktif) pada disk data input, trace display.  Execute.

Gambar 3.43 Trace display NMO & Stack.  FileExit/continue flow.

Migrasi Kirchhoff 1. Flow  07. Migrasi Kirchhoff  Editing flow add : Disk Data Input, True Amplitude Recovery, trace muting, trace length, automatic gain control, poststack Kirchhoff 2D time migration, prestack Kirchhoff 2D time migration, disk data output, disk data input, trace multing, trace display 2. MB3 (aktif) Disk Data Input, True Amplitude Recovery, trace muting, trace length, automatic gain control, poststack Kirchhoff 2D time migration, prestack Kirchhoff 2D time migration, disk data output, disk data input, trace multing, trace display. 

MB2 Disk Data Input Select dataset : pre_prop

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MB2 True Amplitude Recovery  dB/sec correction start time: 5, APPLY or REMOVE amplitude correction : remove

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MB2 Disk Data Output  output dataset filename : migrasi in time.

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MB2 automatic gain control  AGC operator length : 200

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MB2 poststackKirchhoff 2D time migration  table with RMS velocity parameters : velan1, run type  normal (overwrite)

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MB2 disk data output  output dataset filename : migrasikirchoff

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MB2 disk data input  select dataset : migrasikirchoff

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MB2 trace display  number of ensembels : 1, number of display panels: 1

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Execute

Gambar 3.44 Trace Display migrasi Kirchhoff (1500)

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Pada menu picking pilih pick to mute, kemudian muncul kotak dialog  table selector: mute  apply.

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Kemudian picking pada data yang diinginkan, disini kami mem-picking hanya sampai 1000  save picks  file  exit/continue flow.

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MB2 trace length masukkan nilai length yang diinginkan: 1000

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MB2 trace display  number of ensembels :1 , number of display panels: 1.

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execute

Gambar 3.45 Trace Display migrasi Kirchhoff yang telah di muting (1000)