Reservoir upscaling method with preserved transmissibility

1. A computer-implemented method of characterizing or modeling a reservoir, the method comprising:

a. determining an upscaled permeability along an x-axis for coarse cells;

b. calculating by a processor a transmissibility along the x-axis for the coarse cells;

c. calculating the transmissibility along the x-axis for fine cells;

d. calculating transmissibility multipliers along the x-axis across the coarse cells, wherein each transmissibility multiplier along the x-axis is calculated by dividing the transmissibility along the x-axis across the fine cells by the transmissibility along the x-axis across the coarse cells;

e. determining an upscaled permeability along a y-axis for the coarse cells;

f. calculating the transmissibility along the y-axis for the coarse cells;

g. calculating the transmissibility along the y-axis across the fine cells;

h. calculating the transmissibility multipliers along the y-axis across the coarse cells, wherein each transmissibility multiplier along the y-axis is calculated by dividing the transmissibility along the y-axis across the fine cells by the transmissibility along the y-axis across the coarse cells;

i. calculating the upscaled permeability properties along a z-axis for the coarse cells, wherein each permeability along the z-axis across the coarse cells is calculated by applying a harmonic averaging over non-zero permeability cells, wherein harmonic averaged permeability is calculated by dividing summation of a non-zero thickness by the non-zero permeability along the z-axis across the fine cells;

j. monitoring the transmissibility multiplier along the z-axis across the coarse cells, wherein presence of a zero permeability value in the fine cell on either side of a boundary of the coarse cells results in a zero transmissibility multiplier along the z-axis across the boundary;

k. calculating a transmissibility along the z-axis across the coarse cells, wherein the transmissibility along the z-axis across the coarse cells is calculated by utilizing the upscaled permeabilities from step (i);

l. identifying successive fine cells connected above and below the boundary shared by two successive coarse cells;

m. calculating the upscaled permeability along the z-axis for the coarse blocks identified in step (l);

n. calculating the transmissibility along the z-axis across the coarse cells using the upscaled permeability calculated in step (m); and

o. calculating the transmissibility multiplier along the z-axis across the coarse cells.

2. The method according to claim 1 , wherein to preserve a detoured flow path, vertical permeability and post-processing transmissibility are recalculated.

3. The method according to claim 1 , wherein the method is applied to a Cartesian grid.

4. The method according to claim 1 , wherein the method is applied to a corner-point grid.