ZP

Colored inversion is a robust seismic reservoir characterisation tool, which provides band limited impedance data from seismic reflectivities (Lancaster and Whitcombe, 2000). 

The main part of the process is the color operator design. This simple utility can do this task using amplitude spectrums exported from OpendTect.

The workflow is simple:

• Load seismic amplitude spectrum exported from OD
• Load well based impedance spectrum exported from OD
• Define tresholds graphically (amplitude treshold, well spectrum regression limits, operator length)
• Define polarity and taper parameters
• Export the final operator, and load it into OD

The application is coded in Lazarus using FPC and FFT code of Alglib, and the used icons were modified from FatCow Farm Fresh  Icons. Source files of COLOP project are available for download to build the app on other platforms like OSX or Linux.

Concept and prototype can be found as an IPython Notebook in the filelist, or here.

Attachments:

File	Description	File size	Last modified
COLOP concept and prototype	IPython Notebook	144 kB	2015-05-25 09:39
COLOP Sources	Lazarus Source files of COLOP project	104 kB	2015-05-25 09:37
Demo data	Sample spectrums from F3 dataset	7 kB	2015-05-25 09:37
COLOP	win32/win64 executable	3114 kB	2017-11-05 16:53
COLOP.exe zipped with 7-zip	win32/win64 executable zipped to solve download problem	821 kB	2017-11-05 16:54

The idea of color inversion is simple and straightforward. The Earth's impedance spectrum seems to be fractal, which means that the spectrum follows a power law function, so it is predictable:

The aim of this technique is to find an operator which can transform the seismic amplitude spectrum to match the Earth's impedance spectrum.

The main part of the process is the color operator design. COLOP can do this task using amplitude spectrums exported from OpendTect.

COLOP can work in three modes. Colored inversion mode (CI), spectral blueing mode (SB), and spectral whitening (SW) mode.

In the case of CI mode, operator has -90 degree phase spectrum.

In the case of SB mode, operator is calculated from AR(f), which can be defined by following equation: AR(f)=cfß; ß=alfa+1; and the operator has zero phase spectrum. In SW mode flat (white) target spectrum is the basic assumption.

References:

Lancaster, S. and D. Whitcombe, 2000, Fast-track ‘coloured’ inversion: SEG Expanded Abstracts, 19, 1298-1301.

Blache-Fraser, G., and J. Neep, 2004, Increasing seismic resolution using spectral blueing and colored inversion: Cannonball field, Trinidad: SEG Expanded Abstracts, 23, 1794-1797.

Neep, J. P., 2007, Time variant coloured inversion and spectral blueing: 69th EAGE Annual Meeting, Extended Abstracts, B009. 

COLOP Tutorial

This tutorial demonstrate a workflow based on the public F3 dataset which can be downloaded from the Open Seismic Repository.

Tutorial Workflow:

• Start OpendTect, Open F3 demo project
• Visualize F02-1 well on your scene
• Generate P-Impedance log amplitude spectrum and export it.

• Visualize seismic data using volume rendering at the neighbourhood of the well.
• Generate amplitude spectrum of visualized seismic, export it.

• Start COLOP, load seismic and well spectrums.
• Click on Refresh to calculate raw operator

• Tune your parameters to get the best operator:
  
  • Seismic amplitude spectrum treshold
  • Log frequency range for least squared linear regression
  • Operator length and taper length, polarity

• Check your operator efficiency using QC button

• Export your operator form COLOP, and import it into OpendTect

• Convolve your seismic with the operator to get the band limited impedances

• Apply your attribute on your volume, and enjoy your meal:)