Using ADDZCORN to move individual corners of a single cell

The way we used ADDZCORN above, all the eight corners of the cell were moved rigidly. At times it is needed to move corners individually, either a single corner, or some of the corners. In Eclipse this is done by a rather special syntax in the ADDZCORN keyword. If at least one of ix1, ix2, jy1, jy2 is set to zero, this is a signal that we are operating in single-cell, individual corners mode.

When specifying ix1 ix2 or jy1 jy2 a nonzero value means, “move this corner of cell with defined index”, where “this corner” is defined by the position of the nonzero index. This is best explained by examples, where IV means a nonzero index value:

Figure 19. Examples of use of combinations of cell index and zeros to move individual corners

Some examples of use are shown in Figure 19. In the figure it has been assumed that only the defined cell is affected. The continuity rules to surrounding grid are valid as in the section above, i.e. if the continuity flags are set to the current cell, the movement will not affect neighbour cells, while if the flags are set to the neighbour cell index, the movement will be continuous.

So the complete syntax for the middle example in Figure 19 would be, assuming all six layers are moved,

14. Aquifer Modelling (GRID section)

When a reservoir is produced by pure depletion, the only energy supply available is fluid and rock expansion. The total fluid expansion energy is obviously proportional to the total fluid volume. Hence if it as an example is possible to produce 5% of total fluid volume by pure expansion energy, then the recovery fraction will be much lower if all of the fluid is oil (5% of oil present) than if the total volume is to a large extent water (recovery 5% of oil + water).

Fortunately (in a recovery perspective) many reservoirs are connected to an aquifer, i.e. a huge volume of water. When including such aquifers in the simulation model, it is of course possible to model the water-filled volume explicitly, building the grid sufficiently large to cover the entire water volume. This will normally require many grid blocks, and can increase the model size considerably.

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