Assigning the method

From version 2020.4 onward the application contains the 'Depth and Thickness Uncertainty' workflow, which is the replacement of the 'Structural Uncertainty' workflow in older versions. The new workflow contains a (new) method called 'Multiplier'. For general information about the upgrade, see Upgrade to a new 'Depth and Thickness Uncertainty' workflow as of version 2020.4.

With the Assign Method form (model > 3D Structure > Assign Method) you select the method that determines the way uncertain surfaces and intervals are flexed. Both methods make use of random data sampling, resulting in equally probably depth realizations. You can choose from the following two methods:

Sequential Gaussian Simulation (SGS) - The basis of this method lies in an SGS map, generated with the stochastic modeling method SGS, resulting in spacial variability in surface/interval shift. Per realization, an SGS map is generated. As SGS makes use of a variogram, you enter variogram settings in the next steps of the workflow. The SGS map is subsequently normalized and multiplied with the amplitude of shift per surface to derive to the ultimate shift per surface/interval. You provide the amplitude of shift in the form of a standard deviation. You can optionally apply well correction at wellbore intersections.

Multiplier - The basis of this method is uniform shifting of the entire surface or interval, comparable with bulk shifting. Uncertainty is introduced via a multiplier value, randomly sampled from a probability density function (PDF) which you define in the next steps of the workflow. This multiplier value is multiplied with the amplitude of shift to derive to the ultimate shift per surface/interval. You provide the amplitude of shift in the form of a standard deviation. You can optionally apply well correction at wellbore intersections.

No 'mixing and matching' of methods is possible. The method you select here applies to all uncertain surfaces and intervals of the selected structural model. For both methods there is the option to apply a singular SGS map/multiplier value to all your uncertain surfaces per realization: this ensures that (per realization) all uncertain surfaces shift up or down in a synchronous way (see 'stacking strategy' on the Define Uncertainty form).

To assign the method

From the Model drop-down list at the top of the form, select the Structural Model of interest.

From the Method drop-down list, select the method, i.e. SGS or Multiplier.

Click OK at the base of the form to move to the Define Uncertainty form (next step of the workflow) or click Apply and keep the form open.

In case you applied a different method previously (and entered settings in the subsequent workflow steps for that method), those settings will be removed upon clicking Apply or OK at the base of the form. A warning message will be prompted.