CO2 Storage and Utilization in Heterogeneous Carbonate Reservoirs Using Nanoparticle Stabilized Foam

Abstract One of the ways to reduce CO2 emission is to store it underground in aquifers and depleted oil / gas reservoirs. The storage in oil/gas reservoirs is a financially attractive solution because CO2 can be utilized to enhanced oil and gas recovery. However, the sweep efficiency of CO2 injection into carbonate oil reservoirs is poor due to viscous fingering, gravity override and heterogeneity. Water-Alternating-Gas and foam flooding have been developed to improve sweep efficiency. Many carbonate reservoirs have high temperature and high salinity (HTHS). Identifying foaming agents for HTHS reservoirs is a challenge. This study aims to evaluate CO2 storage and oil recovery for foaming agents (surfactants and nanoparticles) in HTHS carbonate cores. Experiments were conducted at a temperature of 90 °C and 255,000 ppm salinity in Indiana limestone cores to represent HTHS conditions. Graphene Quantum Dots (GQD) NP was prepared in house. Surfactants and nanoparticles (NP) were screened at these HTHS for aqueous stability, foam stability, and apparent foam viscosity. Finally, core flood experiments were performed in heterogeneous Indiana limestone cores at a temperature of 90 °C and a pressure of 2000 psi to evaluate CO2 storage and oil recovery. Bulk foam experiments demonstrated that a zwitterionic surfactant had the highest foamability and foam stability at the HTHP conditions. The synergy between surfactants and NP was demonstrated by coupling them in stability tests with and without oil. Shear thinning behavior was observed in all foam rheology experiments. A minimum shear rate was identified for foam generation with each foam formulation. NP-stabilized foam injection in heterogeneous Indiana limestone improved both oil recovery and carbon storage compared to both continuous gas injection and WAG injection schemes.