NEW KEYWORDS AND OPTIONS ADDED TO IMEX 95.00 Reservoir Description
IMEX 95.00 now allows corner point input. Several different methods for entering corner point data are allowed.
*GRID, *CORNER
This option allows the entry of corner point grids. Corner point grids are made up of blocks defined by their eight corner points. Each corner point is described by giving its x, y and z coordinate values, which gives its location in the reservoir.
*COORD
This options causes the reading of information defining the "x"- and "y"-coordinate locations for all corner points defining a *CORNER grid. Since the corner points must lie on vertical lines, there being exactly (ni+1) * (nj+1) such lines, and since definition of a line requires the specification of two points, each requiring the specification of three coordinates, *COORD expects to read 2 * 3 * (ni+1) * (nj+1) values.
*XCORN
This option will cause the reading of all the (ni+1) * (nj+1) * (nk+1) "x"-coordinate values required to define the lateral locations of all points defining a *CORNER grid.
*YCORN
This option will cause the reading of all the (ni+1) * (nj+1) * (nk+1) "y"-coordinate values required to define the lateral locations of all points defining a *CORNER grid.
*ZCORN
This option causes the reading of all depths ("z"-coordinates) of all the corner points required to define the grid.
*CORNERS
This options causes the processing of 3*(8*ni*nj*nk) values, with the first group of 8*ni*nj*nk values giving all the "x"-coordinates of all corner points, the second group giving all the "y"-coordinates, and the third group giving all the "z"-coordinates.
58 • Introduction User's Guide IMEX
Rock-Fluid Properties
*KROIL
This option allows the specification of different methods for the evaluation and determination of Kro, the 3-phase oil relative permeability. These methods are Stone's first model; Stone's second model as modified by Aziz and Settari; and the linear isoperm method.
*STONE1
This specifies the use of Stone's first model for computing Kro. The Krow and Krog values may be looked up as functions of either Sw and Sg or as functions of 1-So and 1-Swc-So.
*STONE2
This specifies the use of Stone's second model for computing Kro. The Krow
and Krog values may be looked up as functions of either Sw and Sg or as functions of 1-So and 1-Swc-So.
*LINEAR_ISOPERM
This specifies the use of the LINEAR ISOPERM model as proposed by L.E.
Baker. The method allows the specification of straight-line segments along which Kro assumes a constant value.
Well Management
*GLIFT, *RATE, *GLR, *OPT
Gas lift rates can now be specified in three ways:
1. Input lift gas rates directly using the *GLIFT *OPT *RATE keywords.
2. Input a gas-liquid producing ratio using the *GLIFT *GLR keywords.
The lift gas injection rates will be calculated from the current time- step's production data. However, the lift gas rates will not be used for the calculation of production rates until the next timestep.
Lift_gas_inj = GLR_input * Total_liquid_est - GOR_est * Oil_rate_est 3. Gas injection rates will be calculated automatically using the values
specified in the *GLOPT keyword.
These rates can be modified at specified dates and times in the Well and Recurrent Data section.
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*GLCONTROL
This option allows the specification of gas lift constraints for a given set of production wells. The specified operating constraints are checked at every timestep. If one of the constraint is violated, then the well or group of production wells will be put on gas lift. The operating constraints that can be specified are: wellhead pressure, bottomhole pressure or stock tank oil rate and maximum water-cut. A hydraulics table can also be specified, which is used for wellbore hydraulics calculations when the well or wells are switched to gas lift. The operating constraints can be changed at specified times or dates in the Well and Recurrent Data section.
*GLOPT, *MAXGAS, *RECYCLE, *GLOPT-TIME
This option will automatically optimize gas lift injection rates to provide maximum oil production rates for the specified wells. The total lift gas available can either be input directly using the *MAXGAS keyword or indirectly from the field's gas production rate through the *RECYCLE keyword. In either case, a portion of the available lift gas can be specified for compressor consumption. This consumption rate is proportional to the total lift gas injected. An iterative procedure is used to determine the
optimum lift gas allocations to each well. A minimum gas-cost factor, below which gas lift injection uneconomic, can also be specified. This can be used to ensure that large volumes of lift gas are not allocated for small incremental oil volumes. The values specified with this option can be modified at dates and times specified in the Well and Recurrent Data section.
OLD OPTIONS NO LONGER SUPPORTED BY IMEX 95.00
The *WELLDPS option and the *DP_PSEUDO option are not supported by IMEX 95.00.
NEW KEYWORDS AND OPTIONS ADDED TO IMEX 94.00 Fluid Properties
*DIFLIB
This option allows for the input of differential-liberation tables. These tables are converted by IMEX to PVT tables (corrected for separator conditions).
*LIGHTOIL
Use a black-oil model, modelling flow of oil, water, and gas. Separate Bo, Rs and two parameters alpha and beta are used to convert stock tank rates to reservoir rates. Alpha is the gas shrinkage factor and beta is the liquid drop out from the gas at stock-tank conditions. This option is useful for those fluids which behave like an oil at reservoir conditions, but are so light that at surface conditions liquids drop out of the gas. This option uses the method outlined in Rovere, A., Sabathier, J.C. and Codreanu, D.B., "Modification of a Black-Oil Model for Simulation of Volatile Oil Reservoirs".
60 • Introduction User's Guide IMEX
*PVTLO
This keyword indicates PVT input for the light oil option.
Initial Conditions
The keywords for initial conditions specifications have been completely re-written. However IMEX will accept all the old keywords as before. A depth averaged (*DEPTH_AVE) initialization option has also been added. A description of all the initialization options can be found in Section 8 under the heading Notes on Initial Conditions.
Well Management
The group-well structure can now be changed at any time. Wells can now be moved from one group to another.
Dimensioner
The IMEX 94.00 dimensioner has been improved to dimension the common block tightly.
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