Welcome to G_Seis’s documentation!

About

Simple 2D-Seismic data processing GUI application

Functionality

  1. SEGY read/write (reads to binary file of format single)

  2. visualize data with three keys sorting

  3. surface-consistent first arrival (or amplitude) decomposition according to 2, 3, 4 factor model

  4. interactively build velocity model based on decomposed arrival picks

  5. perform static, amplitude and spectrum correction (deconvolution)

  6. perform some basic header and data arithmetic

Usage

The main file is G_Seis.m

Before running the application one should:

  1. set path to the root folder and include all the folders inside it

  2. build mex function in /g_other folder. Commands >> mex -setup and >> mex typecastx.c (or >> mex g_other/typecastx.c depending on current path) may help

  3. run the app: >> G_Seis

API

API is presented for each GUI window

Read SEGY

SEGY reader translates SEGY files to G_Seis internal format: binary header is presented as Matlab’s .mat-file and traces along with trace headers are in .bin-file of type float32.

read segy window

Note

Use View data to check if SEGY parameters are correct.

Write SEGY

SEGY writer translates G_Seis internal format to SEGY.

write segy window

Note

IBM32 is known only in seismic exploration. Translation it to IEEE32 is pretty painful: that is why there is no support for writing it.

Read Horizon

Horizon reader translates textual column oriented files to Matlab’s .mat-files.

read horizon window

Horizon files may be used when selecting areas for computing factors.

Use LineEdit widget to set trace header index for each column. For Z values use letter t.

Note

Use View button before reading.

Header Math

This module is dedicated to trace header calculations.

header math window

Use ComboBox to choose trace header that should be edited.

In LineEdit type a mathematical function using Matlab syntax for vectors.

Select From trace and To trace LineEdits before displaying values in the table.

Examples:

  1. compute CDP_X: (SRCX+GRPX)./2

  2. make DSREG (offsets) absolute: abs(DSREG)

Trace Math

This module is dedicated to trace calculations.

trace math window

In LineEdit type a mathematical function using Matlab syntax for column-vector.

Variables FILE_1 and FILE_2 may be used to perform caomputations on selected datasets.

Examples:

  1. sum each trace from FILE_1 with FILE_2: FILE_1(79:end,n)+FILE_2(79:end,n)

  2. filter FILE_1 with moving average filter: filter(ones(5,1)./5,5,FILE_1(79:end,n))

Note

78 is the number of trace headers (they are skipped when computation starts with 79 index). n is the iterator used in loop by traces.

Note

FILE_1 and FILE_2 must have the same number of samples and traces.

Scale Data

Performs traces multiplications by scalar.

scale data window

SC Decomposition

Solves system of linear equations to decompose amplitudes or spectrums by factors. Computed factors then used by SC Apply module to apply amplitude correction or deconvolution.

sc decomposition window

SC Time Decomposition

Solves system of linear equations to decompose timefield by factors. Computed S (source) and R (receiver) factors then used by SC Apply module to apply static shifts and by SC Build Vel Model to perform interactive corrections.

sc time decomposition window

Choose horizon with first break picks.

Set the limits by offsets or by picks for each layer.

There are two mathematical models:

  1. F(i,j) = S(i)+R(j)+M(cdp)*|i-j| for refracted waves

  2. F(i,j) = S(i)+R(j)+M(cdp)*|i-j|^2 for relfected waves

In Special Conditions section set the parameters to regularize the solution.

For more information see:

Taner T.M., Wagner D.E., Baysal E., Lu L. A unified method for 2-D and 3-D refraction statics // Geophysics, 1998, vol. 63 (1), pp. 260-274.

SC Apply

Exclude computed factors (amplitude or static shifts) from the data.

sc apply window

Note

Factors file is a .mat-file computed with SC Decomposition or SC Time Decomposition

SC Build Vel Model

Interactive tool for building and editing layered velocity model from computed time factors.

sc build velocity model window

Sort Traces

Sorts traces in ascending or descending order

sort traces window

Plot Data

Plotting is for traces and computed factors visualization.

plot data window

P_KEY - is primary key.

S_KEY1 and S_KEY2 - secondary keys.

Keys are needed to sort data before displaying.

Absolute values of MIN and MAX values are helpful to restrict the desired data.

In case of displaying factors only P_KEY is used wich should be set to SEQWL.

To display S (shot) factor for first layer choose MIN and MAX equal to 1. For the second layer use 11. For the third layer use 21.

To display R (receiver) factor for first layer choose MIN and MAX equal to 2. For the second layer use 12. For the third layer use 22.

To display M (offset) factor for first layer choose MIN and MAX equal to 3. For the second layer use 13. For the third layer use 23.

To display G (cdp) factor for first layer choose MIN and MAX equal to 4. For the second layer use 14. For the third layer use 24.

Note

Use Header Math module to view headers of computed factors.

indexes and tables