NOTES FOR IMEX 2002.10
The recommended procedure for running on a dual processor Pentium III or Pentium 4 is to use the two command-line arguments “-doms –parasol” described in “Numerical” below.
The “-doms” switch enables parallelization of the Jacobian building and some other non-solver portions of the code.
The “-parasol” switch enables the use of the parallel linear solver, Parasol, instead of the usual non-parallel solver, AIMSOL.
The use of either of these parallel IMEX optionsrequires that you have a license with
“Parallel IMEX” enabled.
Parasol will in general give slightly different answers than AIMSOL, as it is a different iterative solver.
There are a number of additional options related to Parasol and the parallel Jacobian building.
These are described below and in the Numerical Methods Control section of this manual.
The “-aimsol” command line switch overrides PARASOL related keywords and forces the use of AIMSOL.
This version has a correction for the *SCONNECT Keyword when used with dual porosity and dual permeability models.
The use of *MODSI units has been corrected in the aquifer model.
The *MAXRES convergence tolerance has been made more consistent when used with the Polymer option. This will correct problems encountered in convergence when dispersion coefficients are used.
The 2002.10 release changes the time unit of *DISPI, *DISPJ and *DISPK from seconds to the unit defined by the users choice of *INUNIT. The user must change data accordingly.
A problem with WHP controlled wells getting unphysically large pressure derivatives has been corrected.
The use of the *ONTIME feature with *WHP controlled wells has been corrected.
If the head is changed for a temporarily shut-in well, then, if it is reopened during the same timestep it is reset to its original value.
If a well has its constraint type changed during apportionment, its bottom hole pressure is re-initialized. This produces more consistent results.
For pseudo-miscible runs, there may be a slight drift in answers. Smoothing for So-Sorms has been made more consistent.
Handling of oil phase disappearance has been made more consistent.
For non-physical pressures (less than zero), if they occur in a block which contains a well, the corresponding well is temporarily shut in.
The handling of non-physical pressures during convergence has been improved.
26 • Introduction User's Guide IMEX
The crossflow handling of injectors has been improved to correctly account for crossflowing solution gas.
Special release 64 bit versions of IMEX have been created for Itanium WinXP 64-bit and Power 3, 4 AIX 5.1 IBM RS6000’s.
The *MODEL *LIGHTOIL Option is undergoing major revision and is not currently available. Please contact CMG Support for more information.
NEW KEYWORDS AND OPTIONS ADDED TO IMEX 2002.10 Numerical
Command line arguments:
-doms
which is equivalent to
*DPLANES
and overrides the DTYPE/DPLANES keywords in the dataset, and -parasol
which is equivalent to the
*SOLVER *PARASOL
*PPATTERN 2 keywords -aimsol
which overrides any parasol keywords in the Numerical Methods Control section and forces the use of AIMSOL.
Non-solver parallelization of IMEX:
*DTYPE
Complete storage grid array input of Jacobian domain numbers.
*DPLANES imxdom
imxdom target number of planes per domain – Planes are chosen in the dimension with the largest number of non-trivial planes. imxdom is the number of corresponding non-trivial planes in this direction per domain. If imxdom not specified and DPLANES is, then the default is 4.
*PNTHRDS
Number of threads to be used - if parallel Jacobian building and Parasol are not specified, then defaulted to one. If parallel Jacobian building or Parasol is specified, then it is defaulted to the min of (the number of processors in current machine, 2).
If PNTHRDS is set to a number greater than the number of processors, performance will degrade.
If PNTHRDS is set to greater than two then the solver PPATTERN should be changed in order to load balance properly, otherwise poor performance is likely to occur.
User's Guide IMEX Introduction • 27
Keywords related to PARASOL:
*SOLVER (*AIMSOL | *PARASOL)
Choose which solver to use, AIMSOL or PARASOL.
Default if no *SOLVER keyword is *SOLVER *AIMSOL.
*PNSUBD nclas2
Choose the number of PARASOL classes used for vector operations in the GMRES iteration. Default is 2.
*CHECKRB (*ON | *OFF)
When ON, red-black ordering is abandoned for a PARASOL class in which the fraction of red blocks is too small.
Default is OFF.
*PDEGAA idegaa
Factorization degree to be used within PARASOL classes. Default is the value of *SDEGREE (1 for red-black, rcmrb; 2 for natural, rcm).
*PDEGAB idegab
Factorization degree to be used between PARASOL classes. Defaults to idegaa + 1.
*PPATTERN ( ipatrn | *PARTITION | *PPARTITION | *GPARTITION | *APARTITION ) PPATTERN sets the basic partitioning of the reservoir into non-connected regions and separators that makes possible the parallelization of the linear solution. Default is *PPATTERN 2.
Please see the Numerical Methods Control section for a complete description of the *PPATTERN keyword.
Well and Recurrent Data
There are two major additions to the well data for this release: The introduction of reporting groups (the *REPORTING-GROUP keyword) and the addition of a bottom-hole fluid (BHF) group production rate target and monitor.
The purpose of the reporting groups is to allow reporting of results for well aggregates which are very flexibly defined, without the restrictions which apply to the hierarchical groups through which group controls are imposed.
*REPORTING-GROUP ‘reporting_group_name’ well_list ‘weight_list’
*REPORTING-GROUP allows the user to define a set of wells with differing membership weights. No Group Control can be specified for a reporting group, but there are no restrictions placed on well membership in reporting groups. The weight_list allows the reporting group to handle element of symmetry output.
28 • Introduction User's Guide IMEX
The BHF group target allows group production strategies to be set during prediction runs which may better allow reservoir pressure to be maintained while respecting maximum rate limits upon injectors when used in combination with the injection voidage replacement target.
*GCONP ‘group_name_1’ … ‘group_name_n’
*MAX *BHF value action
*GCONP ‘group_name_1’ … ‘group_name_n’
*TARGET *BHF value action
*GCONP … *MAX *BHF and *GCONP … *TARGET *BHF : allow the user to control bottom-hole fluid group production rates.
*GCONM ‘group_name_1’ … ‘group_name_n’
*MINBHF value ( *STOP | *SHUTALL)
*GCONM … *MINBHF: allows the user to monitor group bottom-hole fluid group production rates.
*GUIDEP *BHF ‘group_or_well_list’ ‘guide_rates’
*GUIDEP *BHF: allows the user to specify guide rates proportional to bottom-hole fluid rates.
There is also a minor keyword addition in this section. The keyword *NWFHYS has been added to give users extra control over some aspects of the numerical method used to compute the bottom-hole pressure which yields a specified tubing head pressure. In nearly all cases the default will work well and the user need not be concerned with this keyword. Please see the relevant manual pages for more detail.
*NWHYFS
well_list Integer_list
User's Guide IMEX Introduction • 29