volume calculation uncertainty
DESCRIPTION
Volume Calculation UncertaintyTRANSCRIPT
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Calculating Volumetrics for a Net thickness 3D Grid based on a Cut-off Value & Ranking based on that
Volumetrics Result
Petrel Uncertainty Workflow
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Scenario
Preliminary study needed to identify areas of focus (which will then be
modeled in detail)
The net thickness has been measured at each well location for the
whole basin/region/etc.
The objective is to calculate the volumetrics for the areas where the
net thickness will be greater than a threshold value (in this example, 15
m will be the cutoff value)
This area is
to be ignored
This area has
thickness >15m,
so we want to
calculate the
volume for it
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Part I
Creating the Base Case: a Net Thickness
Simple 3D Grid
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Initial Set-Up
In this presentation, these thicknesses have been converted to a point
set (right-click on the Well Top Attribute > Convert to points)
Well also be using two surfaces: one 0-thickness one for the bottom of the 3D grid, and one 15m one for the cutoff value
Some points are below
the cutoff value
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Creating the 3D Grid
Use Make simple grid and choose Skeleton only, typing in 0 as the base limit and a value above your net points data range for the top
limit
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Subdividing the 3D grid
Use the surfaces and the
point set as input, making
sure that the cutoff surface
is a base
That way, the top zone will be thicknesses above the
cutoff value only
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Creating Properties: Zonation Information
Create a Zone Property: Geometrical modeling >
Zone Index > From all zones (in hierarchy)
The bottom zone ends up with a code of
1 in this case; well need to convert that to a code of 0 so that the following steps
work:
Go to the Properties Calculator and convert the bottom zone to a
code of 0:
NewDiscrete=If(Zone_hierarchy
=1,0,1)
Attach to General discrete template
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Editing the Property
Go to the new propertys Settings > Operations tab and select the Sum vertically option
Make sure that Sum inside zones only is toggled off & hit Run
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Calculating Volumetrics
Go to Volume calculation and create a
new case & fill it with constant values
that have been estimated for the
field/area/basin (alternatively, you could
model the properties but this is meant as
a very broad first pass)
Under the Facies option, use the discrete property created earlier
In the Report Settings, make sure to have the Facies selected
When you run the volumetrics, youll get a result for the Code 1, which will
be for areas where the Net thickness
is greater than the threshold value
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Part II
Running Uncertainty on this Net
Thickness 3D Grid
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Initial Uncertainty and Optimization Workflow
The original workflow will be missing some of the more manual steps
that were used in getting the results
Make sure to add in uncertainty (convert
fixed values to variables)
Some sample parameters that
can be used for uncertainty in
the Make horizons process
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Editing the Uncertainty Workflow
You will need to add to the uncertainty WF the
Geometrical Modeling process and select to edit
the Zones property
You will also need to add in the
Property Calculator statement and
the Sum Vertically Operation (use
the same settings as when you
were creating your base case)
You will need to figure out which row
& column the volume values are
sitting on in the Volume output sheet
(look at your base cases Volumetric report to find out)
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Results of the Uncertainty Workflow
Once you run the uncertainty workflow, you can sort the cases in the
Variables spreadsheet based on this volume of interest
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Optional: Output Net Thickness Surfaces
If you wish to save output surfaces, create a folder in your Input pane (i.e., Output Net Surfaces)
Add in lines to extract the surfaces: Convert horizon to surface, Set name to rename the surfaces, and Move to store them in the Output Net Surfaces folder