Abstract: Lasseter et al. (1986) proposed that scale-up of prtrophysical property should be done from the scale of a representative elementary volume (REV), a volume for which the measured property does not change with an increase in scale over a given limit of scale. The notion of REV has been a controversial concept because its definition is not clear-cut, and it didn't address how to obtain it in real reservoir system. There has even been some argument as to whether REV really exists. This paper, based on the REV concept, proposes the new idea of a REVG (Representative Elemental Volume Grid). The REVG is applied to best describe the heterogeneity of an original reservoir model for a given scale. Mathematically, in REVG system, the variance of properties will be smallest within each grid, and biggest between grids. REVG is the physical target for upscaling in reservoir simulation.

Key words: reservoir upscaling, representative elementary volume (REV), representative elementary volume grid (REVG)