In this article, the GRID and the EDIT section of the Volve_2016_EXPAND.DATA are explained.
GRID
The GRID section determines the basic geometry of the simulation grid and various rock properties (porosity, absolute permeability, net-to-gross ratios) in each grid cell. From this information, the program calculates the grid block pore volumes, mid-point depths and inter-block transmissibilities.
NEWTRAN
This keyword instructs the simulator that transmissibilities are calculated from cells corner positions which is also important for fault transmissibilities calculations.
Image: Corner Point positions used to calculate transmissibilities
GRIDFILE
2 0 /
This keyword is to produce an extended GRID file without EGRID. GRID file contains inactive cell data, non-neighbor connection data, local grid refinement data and local grid coarsening data.
MESSAGES
8* 600000 140000 2* /
Messages are divided into six levels of severity, with each level having its own Print and STOP limits. Here, the first eight and last two parameters are set to default.
NOECHO
This keyword is to prevent output of large included files and decrease number of printouts during a run.
NOECHO has no associated data.
MAPUNITS
'METRES'
Setting the MAPAXES data units to Metres.
MAPAXES
432156.531 6476477.000
432156.531 6481452.000
437531.531 6481452.000 /
MAPAXES specifies the Map and Grid Axes distances, it is generated by a grid pre-processor
Meaning of MAPAXES Keyword:
MAPAXES
2700 3900 3000 4000 3100 3700 /
GRIDUNITS
'METRES'
Setting the Grid units to meters.
SPECGRID
108 100 63 1 F /
Number of grid units (cells) in the X, Y & Z directions (108 x 100 x 63) in one (1) reservoir is considered. The coordinates are in cartesian type (F)
COORD
0.000 4975.000 3131.608 0.000 4975.000 3131.608
49.769 4975.000 3131.608 49.769 4975.000 3131.608
99.537 4975.000 3131.608 99.537 4975.000 3131.608
149.306 4975.000 3131.608 149.306 4975.000 3131.608
........./
The Corner point geometry is used, indicating X & Y coordinates of each grid cell corner point, this type of geometry allows a flexibility in grid definition and has been used for decades, allowing the reservoir engineers to model complex faults geometries and pinch-outs
ZCORN
3131.608 3131.608 3131.608 3131.608 3131.608 3131.608
3131.608 3131.608 3131.608 3131.608 3131.608 3131.608
3131.608 3131.608 3131.608 3131.608 3131.608 3131.608
......./
ZCORN is the elevation of each corner point defined by its X & Y coordinates in the previous keyword.
ACTNUM
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 ...... /
Active Cells are defined by number one, and inactive cells are defined by 0, this option is used to eliminate the inactive cells of the surrounding rock around the reservoir.
FAULTS
-- NAME IX1 IX2 IY1 IY2 IZ1 IZ2 FACE
'F1_S' 69 69 19 19 1 63 'X-' /
The fault section is defined by its name, lower and upper coordinates regarding the X, Y & Z direction, the fault face might be set negative to indicate the opposite face, in this case X-.
PORO
0.190203413 0.196076423 0.00100000005 0.210039079 0.204796657
0.00100000005 0.223142147 0.22258234 0.216002196 0.208192855
...... /
The porosity is defined for each cell by this keyword, the simple fraction porosity is input using a pre-processing software.
PERMX
0 0 0 0 260.983063
270.280182 277.456512 0.00100000005 336.850647 261.801819
0.00100000005 367.354309 429.843536 313.10083 301.436401
309.596558 313.582703 261.521851 197.716797 172.096939
166.239349 162.846146 143.447296 121.489761 137.826401
...../
The permeability of each cell for the X direction is introduced, then PERMY is made equal to PERMX, in the next keyword, the reservoir is considered isotropic through the horizontal plane.
COPY
'PERMX' 'PERMY' /
Permeability in the Y direction is set to be equal to the one for the X direction, for each reservoir cell.
PERMZ
0 0 0 0 78.2949219
81.0840607 83.2369537 0.000100000005 101.055199 78.5405502
0.000100000005 110.206299 128.953064 93.9302521 90.4309235
....../
Permeability for the vertical direction Z is set to be equal 30% of the one in the X direction, then the values are introduced into the simulation model file.
Image: Permeability in the X and Z direction for the Volve Simulation Model
MULTFLT
'F1_S' 1.0000 /
'F10_E' 0.0000 /
'F2_S' 1.0000 /
'F3_S' 1.0000 /
.... /
This keyword enables the use of multipliers for faults of the reservoir model. The faults are modelled using transmissibility multiplier equal to 1 if the are considered able to transmit fluid through their faces and 0 to close the faults, for Volve model, this option helped the history matching of pressure decline and water movement from aquifer and injection wells.
INIT
This keyword is used to ensure the initial file is generated by the pre-processor, this gives the Volve reservoir engineer an insight on the initial static state, with rock properties.
MINPV
50 /
All the active cells which have a pore volume lower than 50 cubic meters are disactivated in Volve field model, this allows us to eliminate small porous volumes zones. It has a benefit for the solver as it harmonizes the solution matrix and helps reducing simulation time.
PINCH
0.3 'NOGAP' /
Any two layers with a pinch-out “Gap between layers” of strictly less than 0.3 meters, will have their transmissibilities generated to ensure flow between the two layers.
RPTGRID
'ROCKVOL' /
A visualization keyword needed to output the rock net and gross volumes, this is used for quality check.
EQUALS
'MULTX' 0.001 83 83 40 46 1 16 /
'MULTX' 0.001 83 87 40 40 1 16 /
'PERMX' 0.01 1 108 1 100 16 16 /
'PERMY' 0.01 1 108 1 100 16 16 /
This keyword here has been used by Volve Reservoir engineer to adjust manually the transmissibility multipliers of the grid and permeabilities in the X, Y & Z Directions. This is based on investigations done through well tests and additional logging acquisitions.
FLUXNUM
1 1 1 1 1
1 1 1 1 12
12 12 12 12 12
... /
The flux number region are set the same as Fluid in Place regions, these regions might be used, to specify boundary conditions and run simulations for each flux regions separately.
12 regions are defined and each reservoir cell belongs to one of these regions. For Volve history matching process, the flux regions enable the reservoir engineer to adjust the aquifer, and different regions communications, specifically the presence of faults, requires to treat each region with customized parameters i.e. porosities, transmissibilities, aquifer performances, including pressure and saturations states.
ADDZCORN
50.0 0 65 52 0 1 63 0 65 52 0 /
90.0 65 0 52 0 1 63 65 0 52 0 /
.... /
This keyword allows to adjust the depth of a defined region (three dimensional) it adds a distance to Z direction (ZCORN) here 50 meter for the first box (region) defined by the x from 0 to 65) Y from 52 to 0, Z from 1 to 63.
This adjustment is made after further investigating the reservoir using advanced data acquisitions like Vertical Seismic Profile (VSP), Well Tests (Transient, drawdown, & Build-up’s) which allows to understand further the reservoir geometry and rock & flow properties.
EDIT
The EDIT section contains instructions for modifying the pore volumes, block center depths, transmissibilities, diffusivities (for the Molecular Diffusion option), and non-neighbor connections (NNCs) computed by the program from the data entered in the GRID section.
EQUALS
-- Tetter lag 23
'MULTZ' 0.1 60 90 38 57 20 20 /
'MULTZ' 0.1 60 90 38 57 22 22 /
'MULTZ' 0.1 60 90 38 57 23 23 /
The transmissibility multipliers of the tetter lag 23 layers are adjusted to 0.1
MULTIREG
-- mul Reg Flux
PORV 0.91 6 F /
PORV 0.91 10 F /
/
The pore volume is multiplied by 0.91, reduced, for the regions 6 and 10.
MAXVALUE
TRANZ 2000.0 1 108 1 100 1 63 /
The transmissibility of the Z direction for the whole reservoir cells is limited to 2000.0.
MULTIPLY
PORV 4.0 84 86 37 45 1 15 /
/
The pore volume here has been increased by 4 times for the defined cells.
-- inc pv for F-11 wct HM
MULTIPLY
PORV 1.2 70 80 37 45 1 15 /
/
The pore volume here has been increased by 1.2 times for the defined cells.
-- inc pv for F-11 i tå
MULTIPLY
PORV 30.0 86 87 39 40 1 6 /
/
The pore volume here has been increased by 30 times for the defined cells.
-- inc pv for F-11 i midt
MULTIPLY
PORV 4.5 80 86 35 40 4 8 /
/
The pore volume here has been increased by 4.5 times for the defined cells.
-- inc pv for F-12 wct HM
MULTIPLY
PORV 20.0 60 60 37 41 6 9 /
/
The pore volume here has been increased by 20 times for the defined cells.
-- inc pv for F-12 wct HM
MULTIPLY
PORV 2.0 55 60 39 41 6 15 /
/
The pore volume here has been increased by 2 times for the defined cells.
-- Increasing pore volume by factor 1.3 along north side of main structure, 2 cells
MULTIPLY
PORV 1.3 86 88 47 48 1 63 /
PORV 1.3 83 85 48 49 1 63 /
PORV 1.3 80 82 49 50 1 63 /
PORV 1.3 78 79 50 51 1 63 /
PORV 1.3 76 77 51 52 1 63 /
PORV 1.3 72 72 52 53 1 63 /
PORV 1.3 73 74 53 54 1 63 /
PORV 1.3 71 72 54 55 1 63 /
/
The pore volume here has been increased by 1.3 times for the defined cells.
-- Increasing pore volume along F-1C in NW structure, 2 cells
MULTIPLY
PORV 4.0 65 66 59 59 1 63 /
PORV 4.0 66 67 58 58 1 63 /
/
The pore volume here has been increased by 4 times for the defined cells.
End of GRID and EDIT Section.
