NEW KEYWORDS AND OPTIONS ADDED TO IMEX 2001.10 Input/Output Control
*SBDZ
IMEX has added subsidence to the grid_list for *OUTPRN *GRID.
*SBDZ
IMEX has added subsidence to the grid_list for *OUTSRF *GRID.
See the Tutorial Section for more information
The user should notice that the display of well rates has been sped up greatly in ResultsGraph, this is due to a ResultsGraph optimization which makes use of extra information the simulator writes to the SR2 binary files.
The *LIST/*NOLIST options for displaying echoed data has been altered. The default under the *LIST option is to display the first 20 lines of data, the remainder of the data is not echoed. This default action can be overridden by placing the keyword *NOLISTLIM in the Input/Output control section.
When output of reservoir condition well variables is enabled, the voidage replacement ratio defined by the group control option is output to the text output file and to the SR2 binary file for display using Results Graph.
Reservoir Description
The grid module routines have been sped up significantly in this release. The improvements will be most evident in large corner-point models where initialization can now take place using approximately one-third the CPU time.
The grid model can now automatically handle the accidental user refinement of null blocks.
Previous versions of the Grid Module would signal an error if this occurred.
The handling of pinchouts has been made consistent between corner point and non-corner point grids. “Pinchout out” connections that may have been previously missed will now be correctly made.
Component Properties
Water properties can now be defined per PVT region. Oil viscosity change with pressure (*CVO) can now be defined per PVT region. The input structure is both backwards
compatible and more flexible than previous versions. The tutorial section has been altered to reflect these changes, please see “Defining Multiple PVT Regions” in the Tutorial Section.
All oil and water properties per PVT region are echoed in the simulator output file (.out).
In addition, it is now possible to define an oil compressibility for each PVT region using
*CO. It is no longer necessary to include a *COT table for each PVT region or include oil compressibility as a function of bubble point pressure in each PVT table to accomplish this.
30 • Introduction User's Guide IMEX
Rock-Fluid Model
Capillary pressure hysteresis in the Pcog table and Krow hysteresis has been added to the simulator. See the keywords below and the *SGT/*SLT keywords for a detailed description of the options.
*HYSKRO
Krow hysteresis using Carlson’s model (non-wetting phase).
*EPSPCG
Pcog hysteresis using Killough’s model.
*RPT *IMBIBITION (*PCOW *PCOG *BOTH)
The user can specify which curve (imbibition or drainage) to begin the simulation on. The specification is done independently for Pcow and Pcog. The *SWTKRTHR and *SLTKRTHR keywords are no longer sub-keywords of the
*SMOOTH keyword (for *SWT and *SLT/*SGT). They are now sub-keywords of *SWT and *SLT/*SGT. This allows the user to change the threshold saturation for endpoint determination without using the smoothing options.
Initialization
The initialization input has been made more flexible when using multiple PVT regions. Now multiple PVT region Contacts (such as WOC or GOC or WGC) can be placed on a single
*DWOC, *DGOC or *DWGC keyword. In addition, multiple PVT region reference depths and pressures can be placed on a single *REFDEPTH or *REFPRES keyword. Please see
“Defining Multiple PVT Regions” in the Tutorial Section for more details.
Contacts and reference pressures are now echoed in the simulation output file (.out) Numerical
*AIM *STAB *AND-THRESH is now the default adaptive implicit method used. This was changed from *AIM *STAB.
Neighbours of implicit blocks have their IMPES stability checked once per timestep, however; neighbours of blocks that have just switched from IMPES to implicit on that timestep are no longer checked. The *AND_THRESH sub-keyword ensures that all IMPES blocks have their maximum saturation and pressure changes checked every iteration for IMPES to implicit switching.
The result of this change is generally a more stable simulation.
Well and Recurrent Data
*GEOA and *KHA
The anisotropic Peaceman well model has been added to the simulator. This model accounts automatically for permeability anisotrophy and gridblock aspect ratio. It is available on the well model based well index calculations (*GEO => *GEOA, and *KH => *KHA). The geometry keyword remains as is, but the geometric factor C (normally 0.37) is ignored as it is calculated internally.
User's Guide IMEX Introduction • 31
This feature is especially useful when used with the *LAYERXYZ and
*LAYERIJK deviated well options.
*LAYERIJK
The new *LAYERIJK keyword allows the user to override, on a layer basis, the well direction input on the *GEOMETRY keyword.
The *LAYERXYZ allows the user to enter trajectory information into the simulator through Builder. In addition, *LAYERXYZ information can be synthesized from Builder without requiring trajectory data.
However, for simple well trajectories, the *LAYERIJK keyword allows the user to model some aspects of well deviation without using builder or requiring trajectory files.
*GMKUPTO *WMKUPTO *SMKUPTO
*GMKMAXR *WMKMAXR *SMKMAXR
*GRECYMAXR *WRECYMAXR *SRECYMAXR
*GPRODGROUP*WPRODGROUP
*SPRODGROUP *GSALESFRAC *GSALESMAXR
*GFUELFRAC *GFUELMAXR
Enhancements to the group recycling options have been made in this version of IMEX. In addition to reducing the amount of gas injected due to fuel and sales gas, options to separately specify maximum recycling rates and total injection rates has been implemented for gas, water, and solvent recycling.
See the *GCONI keyword in this manual as it describes in detail the recycling calculation. In addition, see the manual entries describing the recycling options listed above.
*BHPDEPTH *BHPGRAD *LAYERGRAD
These new keywords allow the user to specify a depth to which a well’s bottom hole pressure is referred to.
The use of quotes in well names is now supported in a consistent manner. To use a double quote in a well name, use a single quote as a well string delimiter. To use a single quote in a well name, use a double quote as a well string delimiter.
32 • Introduction User's Guide IMEX