03 Gridding

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Last updated: Sept 11, 2012Version comment
3 min read

Gridding and surface modeling.

Grid models are essential in modeling reservoirs. Good grid models require good input and well tuned algorithms.

In this exercise we will use as input seismic interpretation lines and closed stick faults. There are seven interpretation sets including the seabed. The reservoir has six horizons. The bottom five have fault lines as input while the top one don't use any faults.

Exercise

Grid a time surface from seismic interpretation and no faults.

  1. Display interpretation lines from 02_Time data > Interpretation lines > 02BasePliocene.
  2. Apply the command Simple points and lines gridding
  3. Click Update window to get the project window as the grid window.
  4. Set x and y increment to 500.

    Grid window for Course B1

    • xmin = -188000, xmax = -47500; ymin = 7864500, ymax = 7959000
    • Using grid increment 500 gives as size of grid: number in rows: 282 , number in columns: 190
    • It is a relatively small grid, but useful in a course and the size of the project is kept reasonable low.
  5. Check in Apply reference grid or outline and browse in: 01_Cultural > Boundary border_line
  6. Use gridding algorithm Parabolic (default).
  7. Check in for Use two steps gridding. Grid increment will be automatic calculated if blank.
  8. Set moving average as gridding algorithm for 1. step.
  9. Click Execute. The result will be written to the same folder.
  10. Click OK and save the panel with all parameters.
  11. Create a new folder for interpretation grids and cut/paste the result grid into this folder.
  12. Display the result as shown below.

    Displaying color legend

    • The color legend is often displayed with the shell command cco. In the example below the following procedure was used:
    • Screen in 2D mode. Click a cursor point at lower right.
    • Use the shell command: cco rev cur col bla tit Time. The cur argument refers to the cursor position. Look at the reference manual if necessary.


Base Plioscene interpretation lines and border line


Base Plioscene grid

Grid menus using faults

  • The grid menu when faults are included is Gridding points, lines and faults. This menu can also be used when there is no faults, but the one we used is a simpler alternative.
Exercise

Grid a time surface from seismic interpretation and closed stick faults.

  1. Display 02_Time data > Faults > 07SilurianFaultInt_Polygons. This is how the fault polygons comes from Kingdom. They must be edited.
  2. Use Edit points and lines to remove the blobs. See Gridding seismic interpretation with faults.
  3. The correct edited fault lines are in 02_Time data > Faults > CorrectedClosedFaults. Use this if you don't have time to complete the editing.

    Tips when editing fault lines with _blobs_

    • To remove the blobs just delete the two extra points in the blobs.
  4. Apply the command Gridding > Gridding points, lines and faults and activate it on the proper interpretation lines.
  5. Don't alter type of input data (under development). Use default: Single points.
  6. Click Use active window to get the project window into the grid window.
  7. Set the x and y increment to 500. Click Adjust to Increment to secure that the grid window is adjusted to the increments. If the grid window changes update the project window in Project Settings. It is an recommended that the project window and grid window are equal and adjusted to the grid increments.
  8. Click Calculate to get number of elements in rows and columns: 282 x 190.
  9. Go to the Fault Input tab.
  10. Check in Closed stick faults and browse in: 02_Time data > Faults > CorrectedClosedFaults
  11. Clik Test at bottom to do the blanking test. The fault polygon should be filled inside. No lines outside.
  12. Go to the Grid options tab.
  13. Check in Use reference grid or outline and browse in: 01_Cultural > Boundary border_line.
  14. Check in Use two gridding steps.
  15. Go to to Result Grid tab.
  16. Set the saving option to Save in project. The result grid will be saved in the same folder as input unless another folder is browsed in.
  17. Click Execute
  18. A default display of the result grid appears. Delete this and display using Display Contours.
  19. The faults lines have been assigned z values and are located in workspace as closedGenFaults. Transfer them to the project using: folder > New > Workspace Data > closeGenFaults.
  20. Click OK to save the grid panel.
  21. If time, repeat the procedure for all faulted horizons. If not use the data in the course project.


Silurian interpretation lines and faults


Silurian grid with faults and input lines