Calculating Volumetrics for a Net thickness 3D Grid based on a Cut-off Value & Ranking based on that

Volumetrics Result

Petrel Uncertainty Workflow

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

Part I

Creating the Base Case: a Net Thickness

Simple 3D Grid

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

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

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

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

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

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

Part II

Running Uncertainty on this Net

Thickness 3D Grid

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

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)

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

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