Identifying two-phase flow rock types in CO2-brine systems using TEM-function

Abstract

CO2 injection into deep saline aquifers is a feasible solution for mitigating climate change. Prediction of fate and transport of CO2 in subsurface requires accurate numerical reservoir models. A reliable reservoir model needs a precise two-phase flow characterization. Recently, technique of True Effective Mobility (TEM-function) was proposed to characterize multi-phase fluid flow properties of rocks (i.e., dynamic rock typing). In this study, applicability of two-phase flow rock typing in CO2-brine systems was studied using TEM-function. Five and three two-phase flow rock types were found for the studied sandstone and carbonate samples, respectively. Existence of multiple dynamic rock types shows that the injection of CO2 into saline aquifers forms a complex and heterogeneous two-phase flow pattern due to pore space heterogeneity and fluid properties along with in-situ conditions. Relative permeability curves of each two-phase rock type were also studied to check if relative permeability data can reflect two-phase flow characteristics. It was observed that relative permeability fails in establishing a relationship with two-phase flow characteristics in the CO2-brine systems. Furthermore, it was investigated whether the two-phase flow rock types identified by TEM-function establish a relationship with basic rock properties. The results show that the two-phase flow rock types identified by TEM-function establish clear relationships with FZI* (FZI-star).