WELL GROUP CONTROL MODULE ADDED TO IMEX 93.00
IMEX 93.00 has the ability to specify group control for wells in a fairly comprehensive manner. The following features are now available in IMEX.
1. Up to three group levels can be specified.
2. Groups can have target rates. GOR and water-cuts can be monitored and appropriate actions can be taken.
3. Wells can be opened (drilled) automatically to meet target constraints. This drilling can be done automatically based on instantaneous production/injection potentials or can be done in a user specified sequence.
4. Well layers can be shut in and opened automatically depending on the current GOR and water-cut.
5. Wells can be shut in and opened automatically depending on the current GOR and water-cut.
6. In previous versions of IMEX, voidage replacement was based on surface rates of producing wells. It is now based on production at reservoir conditions and thus gives much more accurate results.
7. In addition to surface rates, bottomhole rates can now be specified as well constraints.
8. *GLIFT -- This keyword allows for the specification of lift gas rates for producing wells.
LIMITATIONS OF WELL GROUP CONTROL
This version of well management has the following limitations:
1. A maximum of three group levels are allowed.
2. The top most group level ('FIELD') cannot have wells attached to it. Only other groups.
3. Groups to which wells are attached cannot have other groups attached to it.
4. New wells may be attached to a group at any time, however a well cannot be attached to more than one group. Furthermore a well cannot be moved from one group to another.
5. Group controlled injection fluids are limited to gas, water or solvent only. Oil injection cannot be controlled by groups.
6. The well management module can automatically shut in and reopen well layers when GOR or WCUT exceed a certain limit. When this option is used the layers are sorted according to their depths, in order to open/close layers. Thus if the well is perforated horizontally, the behavior of this option may be unpredictable.
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DATA INCOMPATIBILITIES BETWEEN 93.00 AND PREVIOUS VERSIONS OF IMEX
Although most of the well data are compatible with previous versions of IMEX, there are some incompatibilities.
1. For the pseudo-miscible option (solvent injection) the previous versions of IMEX monitored the gas+solvent-oil ratio when *MONITOR *GOR was used. In this version of IMEX *MONITOR *GOR refers to gas-oil ratio only. If it is desired to monitor the gas+solvent-oil ratio the *MONITOR *GSOR should be used.
2. Minimum rate operating constraints have been replaced by minimum rate monitoring constraints. If a minimum rate well constraint is specified, it is converted automatically to a monitoring constraint and a warning message is printed.
3. Well names now have to be unique i.e. it is no longer possible to have two or more wells with the same name. This is because wells can now be referred to by their names only. Well numbers are optional.
4. *PERFV can no longer be used to perforate wells located in hybrid grids. The
*PERFVHY or *PERFRG keywords should be used to perforate wells located in hybrid grid blocks.
5. The *GATHER keyword and the related keywords *PTARG and *ITARG are now obsolete and cannot be used. The *GROUP and *GCONP, *GCONI and
*GCONM keywords must be used instead.
6. Subkeywords *SRFIN, *SRFOUT, *RESTARTIN and *RESTARTOUT under the
*FILENAMES keyword are now obsolete and will not be recognized. They have been replaced with the SR2 file system keywords: *INDEX-OUT, *MAIN-RESULTS-OUT, *REWIND-OUT, *INDEX-IN, *MAIN-RESULTS-IN and
*REWIND-IN.
NEW KEYWORDS AND OPTIONS ADDED TO IMEX 93.00 Input/Output Control
Water-gas ratio is now printed for gas-water reservoirs instead of water-cut.
*MODSI
This option allows for the input/output of pressure in Kg/cm².
*SECTOR
The *SECTOR subkeyword in the *WPRN and *WSRF keywords now controls the sector and lease line printing frequency to the output and SR2 files.
*OUTDIARY
Printing to the diary-file (normally the screen) can now be controlled by the use of *OUTDIARY keyword.
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Reservoir Description SECTOR OUPUT
The sector output has been revised and considerably enhanced. This option now prints a table of sectors with aquifer influx, and production/injection from each sector, in addition to all the previous quantities.
*AQLEAK
In previous versions of IMEX, the water OUTFLOW from the reservoir into the aquifer was not modelled when the *AQUIFER (analytical aquifer model) was used. If the reservoir pressure climbs above the aquifer pressure, this
implementation can give incorrect results. Thus an option (*AQLEAK) was added to model water outflow into the aquifer when the reservoir pressure rises.
Fluid Properties
*COT
This keyword allows the user to specify oil compressibility as a function of bubble point pressure and block pressure above the bubble point pressure.
Initial Conditions
*GASCAP
In previous versions of IMEX, when *VERTICAL *ON option is used, the gas-cap is initialized not to have any oil EVEN if the immobile liquid saturation from the gas-liquid relative-permeability table is GREATER than the connate water saturation from the water-oil relative-permeability table.
An option (*GASCAP *OIL) is now available to initialize the gas-cap with residual oil.
The SR2 File System SR2 FILE SYSTEM
The output for graphics and restarts is now handled in a completely different way. The graphics and restart information is now output to a set of up to three files.
The new file system called the SR2 file system combines the graphics and restart information for greater space efficiency and smaller output files during run time.
The SR2 file system consists of two or three files. These are the index-results-file (IRF), the main-results-file (MRF) and the rewindable-results-file (RRF). The RRF file exists only if the simulator is directed to rewind the restart record. In such a situation, only the IRF and the MRF files will exist.
The two or three files belonging to the SR2 file system work together. Thus an IRF will be useless without a MRF and vice-versa. The IRF is an ASCII file which is an index to the MRF and the RRF i.e. the IRF is a user readable ASCII file which details the contents of the binary MRF and RRF files. The MRF and RRF files are both binary files and hence cannot be read by the user. However a summary of the contents of the MRF and RRF files can be obtained by examining the IRF.
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SRF FILE
Since the SR2 file system is more flexible and space efficient, the specifications of the SR2 are completely different to those of the SRF. For those user's who rely on the SRF for their graphics and other output processing, a SR2 to SRF converter is provided with this release.
Using this converter any set of SR2 files can be converted to a SRF file.
STRUCTURE OF RESTART RECORD
Due to the new SR2 file system, the writing of the restart record has been completely changed.
Thus it is not possible to use restart records generated by previous versions of IMEX.
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