This recipe shows how to write a GLS script algorithm to make two custom log plot fillings:
- Show the well-bore hole void cavity geometry from the caliper curve.
- Split or partition the whole rock volume into its four main components: The shale volume VSH, The matrix volume VMatrix (sometimes also called rock volume VRock), the free water volume, and the hydrocarbon (gas and oil) volume.
Representing the borehole cavity geometry is straight forward. We just need to define one additional log curve: the caliper curve with a negative sign. Then place a filling using a dark grey color from this negative caliper curve to its left, and a right filling from the caliper's positive curve. The borehole cavity will be rendered symmetrically unfilled by the blank background.
The partition of the rock volume into its four basic components, requires these curves:
- The shale volume curve VSH, already available from the interpreted LAS file with curves VSH, PHIE, and SW.
- The matrix volume curve, solved from total volume equation: VSH + VMatrix + PHIE = 1 (that is, VMatrix = 1 - VSH - PHIE)
- The free water volume curve = SW * PHIE
- The hydrocarbon volume curve = (1 - SW) * PHIE
Once the four rock volume components are computed, we need to define just two cumulative curves:
- Cumulative volume up to Matrix: CumMatrix = VSH + VMatrix
- Cumulative volume up to Water: CumSW = VSH + VMatrix + SW*PHIE
Finally, we simply need to place the four fillings between the curves:
- Green: Left boundary 0.0 to VSH
- Yellow: VSH to CumMatrix
- Blue: CumMatrix to CumSW
- Grey: CumSW to 1.0
You are welcome to freely use the script below for your work, even for commercial projects. But please refer you used, or adapted the script from www.geoloil.com, giving us fair credits. You don't need to type the code, as it comes packaged with the GeolOil built-in data-set.
On a typical Windows installation just follow: [File] -> [Open_GLS_Script] -> [Open] -> [UserHomeDir] -> [GeolOil_DB] -> [GLS_examples] -> [rockPartition.gls] -> [Run]. The script will create a .LAS file called rockPartition.las