The Zone to Zone Transmissibility Multipliers workflow

The permeability of the fault zone is controlled by tectonic smearing, mixing and re-distribution of the fault-slipped sands and shales in the reservoir. Fault permeability and thickness are geological variables that are captured from geological property grids in the model for input to fault transmissibility (Tf) calculation in the Fault Seal Modeling workflow. The Fault Seal Modeling workflow is the preferred workflow because it generates lateral variability in Tf that is constrained by the geological property grids in the model.

With the Zone to Zone Transmissibility Multipliers workflow of the Fault Seal strip (model > Fault Seal > Zone to Zone Transmissibility Multipliers) you can directly enter fault transmissibility multiplier values that are independent of the geological grid properties. These transmissibility multipliers are stored in a Zone to Zone Multiplier Model (Z2Z Multiplier Model) that can be selected as input to a simulation case in the reservoir simulation workflow. A requirement to create such model is a 3D grid with faults. This 3D grid can also be a grid that was upscaled for simulation.

In the workflow, you apply the fault transmissibility multipliers on a zone to zone basis (Z2ZTM). You can also specify a fault-specific transmissibility multiplier (FTM) with the last step of the workflow, that is also independent of the geological grid properties. For Z2ZTM, the zone definition is based on the zone property which you select on the form. Any property of type 'zone' (in the Inspector) is valid for selection, but usually you will use one of the zone properties that defined your stratigraphic zonation, i.e., a property called 'ZoneID_Level <x>' in the Geometry folder under your 3D Grid. Such property represents the zonation of your stratigraphic model and as such the lithological characteristics/sealing capacity of the faults in your reservoir.

The fault transmissibility multipliers (Z2ZTM and FTM) are stored in the Z2Z Multiplier Model. When you select the model as input to a simulation case, the final fault transmissibility (CTRtot) is calculated as follows:

where:

CTRtot = Total transmissibility (m3)

Z2ZTM = Zone to zone transmissibility multiplier (unitless) - to be set with the Zone to Zone TM form

FTM = Fault transmissibility multiplier (unitless) - to be set with the TM per Fault form

CTRno fault = Cell to cell transmissibility (m3)

In the calculation, which takes place in the IMEX, GEM, STARS, ECLIPSE and tNavigator workflows of the simulation strip, each transmissibility multiplier that is not explicitly specified by you is set to 1. This means you can skip the Zone to Zone TM or TM per Fault form if you do not want to specify those multipliers.

This method allows you to specify fault transmissibility per zone connection. Connections with clay-rich zones would typically have a lower transmissibility than connections with sand-rich zones (this is usually captured by the SGR and SSF algorithm choices in the Fault Seal Modeling workflow). In the Z2Z Transmissibility Multipliers workflow, you can enter the multiplier values in a zone to zone connection matrix.

As the workflow works with fault sets (a fault set is a collection of faults with the same shared Z2ZTMs), you only have to specify these values once for all faults within that set. Note that your fault(s) always have to be part of a fault set before you can specify Z2ZTM and FTM. Fault sets are specified with the second step of the workflow. After you have finalized the workflow, the Z2Z Multiplier Model can be selected on the Faults and NNCs form in the reservoir simulation workflows (applicable for IMEX, GEM, STARS, ECLIPSE and tNavigator) of the simulate strip.

For more on the workflow steps, see:

Creating a Z2Z Multiplier Model

Assigning faults

Setting multipliers on a zone to zone basis

Setting multipliers per fault