Pore-Scale Fluid Dynamics Resolved in Pressure Fluctuations at the Darcy Scale

Abstract

Complex pore-scale dynamics have been observed during multiphase flow through porous rocks. These dynamics are not incorporated in large scale models for the migration and trapping of subsurface fluids such as CO2 or hydrogen. We show that fluctuations in pressure measured at the core-scale (centimeters) can reflect fluid displacements at the pore-scale (millimeters). The spectral characteristics of pressure data are shown to depend on the flow dynamics, the size of the rock sample, and the heterogeneity of the pore space. These results show that pressure data, transformed into the time-frequency domain using wavelets, provides information about flow dynamics, across scales, that are otherwise challenging to acquire.