NEW KEYWORDS AND OPTIONS ADDED TO IMEX 98.00 Input/Output Control
Command Line Options:
IMEX 98.00 has several new command line options.
`-f input_data' Defines the input data file.
`-r input_restart' Defines the restart irf file.
`-checkonly' Runs the model in check only mode. An IMEX license is not required for a check only run specified from the command line.
`-dimsum' Prints detailed information on model dimensioning at run time.
`-onestep' Runs the model for one timestep only.
*MAX_GRIDS
The IMEX 98.00 model now has a *DIM *MAX_GRIDS subkeyword to change the default number of refined grids.
*SR2PREC
The SR2 binary file is by default written out in double precision mode.
Single precision output is also possible. Single precision halves the size of most SR2 files. Restart information is slightly effected by the loss of precision.
*OUTPRN *GRID *APIGRAV
The API tracking model allows the printout of light oil volume fraction for each block using the *OUTPRN *GRID *APIGRAV print option.
*LSOLVER
*DEBUG *LSOLVER *ON turns on the debug output of the number of solver failures.
Reservoir Description
Both multilevel refinements and refinements defined in recurrent data have been added to IMEX 98.00. This represents a major improvement in how the user may use IMEX to model complex reservoirs.
A more robust handling of faults has been included as well as a more general implementation of the corner point grid option.
The analytical aquifer model has been reworked, introducing a new option (Fetkovitch aquifer) and improved Carter-Tracy influence function extrapolation and more realistic defaults.
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A feature to input corner point tolerances has been included to allow the user to tune whether blocks are in contact with each other. In addition, this feature can be used to define a
distance within which a blocks corner is assumed to be pinched out.
Sectors can now be input as an array to further simplify input.
The user can now explicitly define 'special connections' between pairs of blocks along with a transmissibility for the connection.
*REFINE
The *REFINE keyword may also occur as part of recurrent data. Refined blocks may appear later in a simulation. *REFINE must be used to set up refinements defined in recurrent data prior to using the *PERFRG keyword which refers to them.
*RANGE
The *RANGE keyword can now refer to single multilevel refinement blocks as well as to groups of fundamental blocks.
*AQMETHOD
The Fetkovitch aquifer calculation has been added to the analytical aquifer calculation (*AQMETHOD *FETKOVITCH).
The Carter-Tracy aquifer calculation has been modified to 1) use more realistic default values and 2) allow more realistic extrapolation of the aquifer influence functions (*AQMETHOD *CARTER-TRACY).
A compatibility option *AQMETHOD *OLD has been included in this release to allow the users to use the same *AQPROP defaulting as IMEX 97.00 and to use the same influence function extrapolation as IMEX 97.00.
*SECTORARRAY
It is now possible, in array input format, to define block which are in sectors.
This allows a streamlined input of sector information.
*SCONNECT
The *SCONNECT keyword can set up a flow connection between any two reservoir blocks. Transmissibility is defined explicitly on the *SCONNECT card.
*CORNER-TOL
The tolerance setting how close to each other corner point blocks have to be before they are considered to be in contact is now user defined.
Component Properties
IMEX 98.00 includes significant additions to the Component Property section.
The phase appearance/disappearance algorithms have been rewritten from scratch to properly account for the disappearance of multiple phases within a grid block (e.g. water and gas within a solvent filled block).
44 • Introduction User's Guide IMEX
An API tracking option was developed (jointly with Petrobras) to model reservoirs with simple compositional gradients.
A gas saturation threshold was added to the minimum solvent saturation to control onset/loss of miscibility in the four component miscible model.
Both the solvent model's gas saturation threshold and minimum solvent saturation have had smoothing applied to the cutoff values, this causes a smoother transition from miscible to immiscible conditions (and the reverse) as well as improved numerical performance.
Previous restrictions which limited the *OILWATER option to use a single PVT region have been removed. *GORINT is no longer valid when used with the *OILWATER option.
*MINSS min_sol_sat' (*SGTHRESH `sgval') (*SMOOTHEND (*ON | OFF))
This keyword controls onset/loss of miscibility at low solvent saturations (min_sol_sat) and low gas saturations (sgthresh). The discontinuity in fluid properties this causes, by default, is smoothed to improve convergence.
*API-INT or *API-INTOW
These keywords signal IMEX to use the API tracking model with free gas (*API-INT) or without free gas (*API-INTOW).
*PVTAPI
This keyword is used to input a gas PVT table (for use with the API tracking option).
*APIGRAD
This keyword is used to input an oil PVT table for each oil density (gravity) specified within a PVT region (for use with the API tracking option).
*GORINT
*GORINT is no longer used with the *MODEL *OILWATER option.
*GORINT continues to be used with the *MISCG model (miscible model with chase gas injection).
Numerical Methods
*NORM *PBUB *MAXCHANGE *PBUB
The *NORM *PB and *MAXCHANGE *PB have been changed to *NORM
*PBUB and *MAXCHANGE PBUB for compatibility with CMG's GRIDBUILDER. Please alter data to reflect this change.
Initialization
The Initialization section has changes which reflect the new API tracking option and the
*SWINIT option.
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*API *APIT
The API tracking option allows for two methods to specify the initial light oil volume fraction in the reservoir. API can either be defined as a grid array or as a function of depth for each PVT region.
*SWINIT
The *SWINIT option allows the user to specify a water saturation and still go through the *BLOCK_CENTER gravity capillary equilibrium option.
*SWINIT can be different from the connate saturation. Equilibrium is achieved by scaling the individual blocks Pcow curve to achieve equilibrium at a specified water saturation.
*GOC_SW *WOC_SW
These keywords allow the user to explicitly define the water saturation above the GOC and below the WOC for each PVT region. These values override the normal defaults assigned when using the *BLOCK_CENTER gravity capillary initialization options and the values assigned using *SWINIT.
Well and Recurrent Data
*RANGE and *REFINE
The capability to define new refined grids in the Recurrent Data section has been added to IMEX. Thus the keywords *RANGE and *REFINE may appear in the well (recurrent) data. Please refer to the Reservoir Description section for information on the usage of these cards.
*PERFRG
The ability to perforate in multilevel refined blocks has been added to the
*PERFRG keyword.
The *PERFRG card now can handle perfs which exist at in layers at different levels of refinement. For example the following is now possible.
Fundamental Refine1
In addition, wells that are accidentally perforated in pinched out or nulled out blocks are now flagged in a more informative manner. A list of valid perfs (with i,j,k locations) is presented to the user, along with a separate list for invalid perfs. It is now a simple process to produce a valid perf list.
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*WELLINIT
The *WELLINIT keyword can now also be defined on a well by well basis.
In addition to the previous usage,
*WELLINIT (*ITER) (*CHANGE) (*TIMESTEP) the format,
*WELLINIT well_list (*ITER) (*CHANGE) (*TIMESTEP) can be used.
*ALTER, *TARGET, *GUIDEI, *GUIDEP, *GLIFT, *ON-TIME, *ALTERCP These keywords listed allow the user a simpler method for assigning all values in a well list to one value. Previous versions of IMEX allowed the user to employ well lists with wildcarding, but values (rates, etc.) assigned to each well had to be entered explicitly (even if one value is used for all wells).
Example
*ALTER 'PRODNW*'
14*1000.0 <--- Input List (14 entries)
Thus the number of wells in the wildcard list had to be known, making input more time consuming.
If the user now specifies a single value in the list input IMEX will now set all wells in the list to this value. This applies to all types of well lists (not just those using wildcards).
*ALTER 'PRODNW*'
1000.0 <--- single entry, all wells in list alter primary constraint to 1000.0
It is not necessary to know the number of wells in the well list to apply the single value to the list.
OLD OPTIONS NO LONGER SUPPORTED BY IMEX 98.00 Input/Output Control
*DIM
The IMEX 98.00 model no longer supports the *DIM *MEMORY_MODEL keyword. The run time dimensioning now makes this backward
compatibility feature unnecessary.
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