Initialization view in STARS™

If you selected a Simulation Concept with a Fluid Model on the Create Case form, the 'Initialization Region IDs', reference pressure, reference depth and fluid level depths will be auto-populated.

Initialization data is composed of one or more initialization regions for which pressure and depth, contact depth, water saturation, and other data is defined. Each initialization region may be associated with a different area of the simulation grid by adding initialization regions in this tab.

Equilibrium tab

This tab contains parameters for describing the initial conditions and equilibration settings.

Initial conditions from restart (INIT_FROM_RESTART) Check the checkbox in the input field if you want to assign a restart file for initialization. The restart file is assigned in the 'step 5' on the Simulation Case form by selecting a 'Source case' and a 'Source date'. The selected restart state is then assumed to be the initial conditions for the active simulation case.

Vertical equilibrium selection (VERTICAL) Specify the vertical equilibrium option. In the input field, click on the ellipsis button to open the Calculation Methods dialog.

Block saturation Select from one of the three options for vertical equilibrium:

  • OFF Do not perform any vertical equilibrium.
  • DEPTH_AVE Perform capillary-gravity vertical equilibrium based on mass conserving depth-averaged method. If you select this option, assign an input for the 'Phase pressure correction'.
  • BLOCK_CENTER Assigns the cell saturation value from the cell center depth.

Phase pressure correction (DEPTH_AVE only) Choose between NOEQUIL and EQUIL. With EQUIL, a pressure correction is added to each phase to achieve gravitational equilibrium during initialization. With NOEQUIL (default), the phase pressure correction is not applied.

Specify initial oil saturation in the gas zone (GASZONE)  Specify the initial oil saturation in the gas zone above the gas-oil transition zone. Select OIL if you want residual oil saturation generated from the gas-oil saturation functions. Select NOOIL if you want zero residual oil saturation in the gas zone.

Parameters tab

The Parameters tab of the Initialization view contains parameters that describe the selected initialization region. The master table for the Parameters tab (located in the left side of the tab) contains a list of initialization regions:

Active  Determines whether initialization region is active.  Inactive regions are not written to the deck.

Name  Name of the region.

Region ID  ID of region used in the deck.

Important  Make sure you undertake the following rules before assigning the Region ID. An error message is displayed if a rule is broken.

1. The Region ID must have a value greater than or equal to 1.

2. The active Region ID numbers must start with 1 and have values increasing by 1.

3. Active models must not have unique Region ID numbers.

Initialization Region Parameters

Pressure (REFPRES)  Indicates input of reference pressure. The reference pressure at the reference depth are used in the vertical equilibrium option, along with the capillary pressures, fluid densities, water-oil contact and the gas-oil contact depths, to calculate the block pressures and saturations.

Depth (REFDEPTH)  Indicates input of reference depth.

Water-Oil Contact (DWOC)  Defines the depth to the water-oil plane.

Gas-Oil Contact (DGOC)  Defines the depth to the gas-oil contact plane.

Gas-Oil capillary pressure at the gas-oil contact (GOC_PC)  Defines the gas-oil capillary pressure at the gas-oil contact.

Water-Oil capillary pressure at the water-oil contact (WOC_PC)  Defines the water-oil capillary pressure at the water-oil contact.

Below Water-Oil Contact (WOC_SW)  Allows you to define the water saturation below the gas oil contact for each PVT Region.

Create water-gas transition zone from gas-water capillary pressure curve (TRANZONE) Use the gas-water capillary pressure curve(s) to generate a water/gas transition zone in a reservoir system that is initially water and gas only. TRANZONE option is enabled only when DWOC and DGOC have same values.