2. The RUNSPEC section

Since the RUNSPEC section comes first in the Eclipse data file it is described here. Many of the terms used in this description will not be defined before later, but are included here for completeness.

The section contains run specification data, i.e. information Eclipse needs at the very beginning of the job, before it commences reading of any other data, typically for determining how much computer memory to reserve for the different kinds of input.

Grid dimension – keyword DIMENS

Specification of the number of cells in x, y, and z-directions:

DIMENS

NX NY NZ /

Example:

The grid is 30 cells in the x-direction, 15 cells in y-direction and 5 cells in the z-direction (vertical) – will also be referred to as 5 layers.

DIMENS

--NX NY NZ 30 15 5 /

Phases

The phase definition specifies how many and which phases are present in the run. Each included phase is specified by one keyword. The alternatives are,

OIL WATER GAS VAPOIL DISGAS

(No slashes)

Example

For a standard three-phase problem we would specify,

OIL

WATER

GAS

Unit system

Specify the unit system the data are defined in (all data must be in the same unit system) Choose one of

17

Start date

Specify the date when the simulation starts, also called initial date or “day 0”. Date format is identical to the format in the DATE specification (see section 8.2)

Example

The simulation starts at April 14., 1997:

START

14 ‘APR’ 1997 /

Unified / Non-unified files (chapter 11)

Specify if unified files are to be used. Non-unified is the default and will be assumed if specification of unified is omitted.

Keywords:

UNIFIN

UNIFOUT

Data checking only

Eclipse can be requested to check the input data syntax without running the simulation. This is done by the keyword

Input errors in the SCHEDULE section will not be discovered before Eclipse encounters them. (Eclipse does not read the entire file before the run starts, only as much as it needs). By routinely doing a data check run after major changes, unexpected terminations of simulations due to data errors can be avoided.

Table dimensions

Eclipse needs to know how many tables we are going to define, and how many entries the tables will have when it sets up the run dimensioning, i.e. when the RUNSPEC section is read.

Technical note: This is because Eclipse is written in FORTRAN, and does not use dynamic memory allocation.

The appropriate keyword is TABDIMS, which contains the following relevant items, (for others, see Eclipse documentation)

1. NTSFUN:

2. NTPVT:

3. NSSFUN:

4. NPPVT:

5. NTFIP:

6. NRPVT:

Example

To set all values to their default:

EQLDIMS

Used to set some parameters for equilibration. Can be defaulted (omitted) in most cases.

18

Well data dimensions

Eclipse must know how many wells to allocate memory for, and how much memory is needed for each well. This is specified in the WELLDIMS keyword, with entries,

MAXWELLS Maximum number of wells in the model

MAXCONNW Maximum number of connections (completions) in each well

The default value for all the entries is zero, so this keyword must be specified if the model contains any wells.

Example

WELLDIMS

NSTACK (chapters 17-18)

To redefine the size of the NSTACK, i.e. the number of search directions to store for use by the linear solver, include the keyword NSTACK. The default value of NSTACK is 10.

Example

To increase NSTACK to 25,

NSTACK 25 /

Aquifer specifications – AQUDIMS (chapter 14)

Specify maximum number of lines in the AQUNUM and AQUCON keywords. (I.e. not the number of connections defined, but the number of lines used to define the connections in the keyword)

Default values are zero, so this keyword must be specified if aquifers are used.

Example

Grid options (chapter 13)

The GRIDOPTS keyword is used to flag that negative index transmissibility multipliers are used. (And some other flags which are not used in these notes)

To allow for MULTX– and related keywords, set

GRIDOPTS

YES /

The default is “NO”, so the keyword is not needed if negative index transmissibility multipliers are not used.

Rock compressibility options (chapter 6)

When rock compressibility is defined by the ROCKTAB (or ROCKTABH) keyword, the keyword ROCKCOMP must be included in the RUNSPEC section. The keyword has two associated items,

1.Specify if rock compaction is reversible (elastic) or irreversible (plastic), or if tables with hysteresis are used. Choices are REVERS, IRREVERS, and HYSTER

2.Number of rock compaction tables (equal to number of ROCKNUM regions)

Example

To specify that ROCKTAB tables are irreversible, and that the model includes three different rocknum regions,

ROCKCOMP

IRREVERS 3 /

19