Pore-scale Multi-phase Flow Analysis: Effect of Cyclic scCO2 Core Flooding in Depleted Oil Carbonates using NMR

In this study, we investigate three phase flow (oil/water/CO2) in carbonate reservoir to mimic CO2 trapping/mobility into a depleted oil reservoir. We explore the cyclic effect of injecting supercritical CO2 (scCO2) into Indiana carbonate core plugs exposed to two different durations of oil-rock exposure (i.e., sample oil aging) using a non-destructive Nuclear Magnetic Resonance core flooding system to monitor fluids displacement into the pore network. The residual CO2 trapping is quantified and located along the sample as CO2 displaced fluids in the core plugs. Moreover, we compare the measurements of some rock properties before and after scCO2 experiments for chemical reactions that would alter the original pore structure.

Our results show the displacement of brine by cyclic CO2 injection only occur in the larger pores while the residual oil remains unchanged. A small reduction in the porosity suggests a possible remobilisation of calcite from dissolution/precipitation mechanisms within a week of CO2 injection.