REV Analysis of Two-Phase Flow in Layered Rocks

What is it about?

A series of numerical simulations of waterflooding are performed in a model made of alternating parallel layers of two rock types. Upscaled relative permeabilities are computed on samples at different lengths, changing from millimeter to kilometer scale. Flow behavior for different samples is analyzed according to capillary, viscous, and gravity effects, which are monitored during the simulation. Although the REV size for some properties such as porosity seems to be the smallest replica block (unit block), our results show that the REV for relative permeability follows a power-law trend and changes with flow rate and scale.

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Why is it important?

Geological/flow properties computed from a heterogeneous rock sample represent the properties of the entire medium if the size of the sample is larger than the size of the representative elementary volume (REV) of the rock. Among these properties, relative permeability is believed to have the most influence on multiphase-flow behavior. Therefore, much care must be taken to ensure that relative permeability has been computed beyond the REV size.