This recipe shows how to make two custom log plot fillings:
 Show the wellbore 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
The figure below displays the borehole geometry in track 2, and the rock partition in track 5.
Setting suitable fillings and crossover curves to split the rock volume into components
Setting the stratigraphy framework, showing formation, members, beds, and completion
Setting curves and tracks to display borehole geometry and rock volume splitting
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