Time-And-Space Averaging Applied to Intermittent Multiphase Flow Experiments

Various researchers have studied fluctuations in pore-scale phase occupancy during multiphase flow in porous media using synchrotron-based X-ray microcomputed tomography (micro-CT). However, the impact of these fluctuations on the concept of a representative volume is not yet fully understood. In this study, we performed spatial and temporal averaging of multiphase flow experiments visualized with synchrotron-based micro-CT, focusing on oil saturation as the key parameter to determine a representative time-and-space average. Our findings revealed that a saturation value representative of both time and space was achieved during fractional flow experiments in drainage mode with fractional flows of 0.8, 0.5, and 0.3. Furthermore, we computed a range of relative permeabilities on the basis of whether momentaneous saturation or time-and-space averaged saturation was utilized for direct simulation. Our results highlighted the importance of time-and-space averaging in determining a representative relative permeability and indicated that the temporal and spatial scales covered in a typical micro-CT flow experiment were sufficient to obtain a representative saturation value for sandstone rock under intermittent flow conditions.