Volume calculation for one or two grids.
Volume calculation for one grid and an isopach or between two grids and optionally two contact planes does not require a layer model and can be done quite easy with a dedicated menu called Volume calculation that is directly visible on a grid. The volume calculation operates with singles values for the petrophysical parameters and singles values or grids for contact planes.
Below is a sample task to illustrate volume calculation.
Calculate HCPV volume for a zone.
We want to calculate HCPV volume between Upper Cretaceous and Base Jurassic in the layer folder for depth grids.
The volume will also be between the contact planes 2500 and 2900 and within the license area.
- Highlight {04_Depth data} {Grids Interpretation} 03Upper Cretaceous and activate Grid Operations > Volume calculation.
- Check in Apply a bottom grid in calculations.
- Browse in {04_Depth data} {Grids Interpretation} 05BaseJurassic as the bottom horizon.
- Set Type of volume to be calculated to Between plane1 and plane2.
- Check in Specify plane 1 level and set the value to 2500.
- Check in Specify plane 2 level and set the value to 2800.
- Check in Use area grid or outline and browse in 01_Cultural Licenses {Licens 07-18}
- Write in values for porosity = 0.4, water saturation = 0.5 and net to gross = 0.6.
- Click Execute to perform HCPV volume calculation.
The result is: Volume calculated from 2500 to 2800: 133.72658 cubic km (E9)
The display options are placed under the Display tab. Open that tab.
Display volume grids.
- Click on Display calculated volume when the combo box is As single volume.
The result is the lower left display. - Click on Display calculated volume when the combo box is On bottom of grid.
- Set a cursor marker with y and click Get cursor values.
- Click Perform cross section from position value.
The result display is shown below to the right.
Volume grid displayed as single volume
Volume grid and cross section displayed on bottom grid; see comments
Comments on _Volume grid displayed on bottom grid_
The picture shows the volume grid draped onto Base Jurassic. The grid is not present outside the area of positive volumes. In addition a cross section is displayed and shows clearly where there are no volume because the top grid is below the bottom contact plane. The cross section study illustrates that clearly.
Display top and bottom grids and contact planes.
- Display the top and bottom grid from the project.
- Display the two contact planes.
- Mark with y a cursor position at the top plane and type the shell command: tx2 col red cur fol txt "GOC 2500"
- Mark with y a cursor position at the bottom plane and type the shell command: tx2 col gre cur fol txt "OWC 2800"
Top and bottom grids and contact planes
Create a cube with top and bottom grids and contact planes.
- Click Create cross section cube.
- Click Activate frame and move the manipulator to see the cross section planes in red green and blue colors.
- Display the bottom horizon.
Cross section cube for gas, oil and water
Calculate area versus depth curve.
- Use exactly the same settings as in Exercise Calculate HCPV volume for a zone.
- Check in Calculate area or volume against depth.
- This exercise will calculate area versus depth and therefore set Calculation is done using: area.
- Push Execute
- The area / depth curve is saved in the project as {Course B1} / 01_Cultural Curves_area_depth 03UpperCretaceous_area_depth_curve.
- Display the area / depth curve by pushing Show curve. The screen is blanked and the area / depth curve is displayed. Instead of using the existing screen window a new window or a new Tab could have been established.
- Write the text Area / depth from 2500 to 2800 at top of the window. This is done most easily by clicking a cursor point (in 2D mode) at top left. Then go to the command shell and write: tx2 cur col bla txt "Area / depth from 2500 to 2800"
- The area / depth factor is set low to have the area numbers small. The real area numbers are muliplied by the factor.
Area versus depth between 2500 and 2800