Representative Elementary Volume (REV) in Spatio-Temporal Domain: A Method to Find REVfor Dynamic Pores

One of the potential risks associated with subsurface storage of CO2 is the seepage of CO2 through existing faults and fractures. There have been a number of studies devoted to this topic. Some of these studies show that geochemistry, especially mineralization, plays an important role in rendering the faults as conduits for CO2 movement while others show that mineralization due to CO2 injection can result in seep migration and flow diversion. Therefore, understanding the changes in reservoir properties due to pore alterations is important to ensure safe long term CO2 storage in the subsurface. We study the changes in the Representative Elementary Volume (REV) of a rock due to reactive kinetics over a time, using a statistical approach and pore-scale CO2-rock interactiondata.The goal of this study is to obtain the REV of a rock property that accounts for pore-scale changes over time due to reactive kinetics, and we call this as spatiotemporal REV. Scale-up results suggest that the REV changes with time when CO2-rock interaction is considered. It is hypothesized that the alteration in pore structure introduces more heterogeneity in the rock, and because of this the magnitude of REV increases. It is possible that these noticeable changes in REV at pore-scale may have an impact when analyzed at the reservoir scale.