An Experimental Investigation of Polymer Enhanced CO2 Foam Flooding: Foam Stabilization and CO2 Mobility Control

Abstract

Abstract Carbon dioxide (CO2) foam mobility control in CO2 storage and enhanced oil recovery can improve the storage potential and oil production by reducing CO2 mobility and increasing reservoir sweep efficiency. A coreflooding study of CO2 foam strength and stability during the co-injection of CO2 and a nonionic surfactant (CO2 foam) solution with and without hydrolyzed polyacrylamide (HPAM) polymers was conducted, including one experiment adding chromium cross-linker solution to the surfactant-polymer solution, to assess gelation effects to assess the effects on improving CO2 mobility reduction. Foam strength, stability, and propagation at unsteady-state flow were compared between the surfactant-based CO2 foam and the polymer-enhanced foam (PEF) solution at 70% foam quality in sandstone cores at scales of 9 cm and 83 cm in length, and rates of 2 ft/day and 4 ft/day. In addition, pure CO2 was injected after foam to identify dynamic changes in foam stability and determine CO2 flow reduction efficiency of the solutions after their placement. Furthermore, the experiment with the 83 cm core added a stage of injection with a chromium cross-linker solution to the surfactant-polymer solution to assess the propagation and strength of the PEF gelled. Apparent viscosity quantified foam strength during co-injections of CO2 foam and CO2 PEF. Adding HPAM polymers significantly increased the foam's apparent viscosity, efficiently creating a stronger foam. PEF propagated at a higher differential pressure compared to CO2 foam, but differential pressure did not increase substantially during the injection of several pore volumes. While the effect of foam injections without polymer was fully reversible during pure CO2 injections, polymer-enhanced foams could significantly reduce the flow of CO2 after placement. The PEF floods high DP showed that the polymer has the ability to block flow channels. The chromium cross-linker with the polymer solution showed that gelation occurred during injection, after which gel entirely blocked the core so CO2 could not enter. Higher rates showed the shearthining behavior of foams and a higher impact on reducing flow mobility during and after the PEF placement. Foam with added polymers may be promising for CO2 mobility reduction during and after placement. Foam has been acknowledged to reduce carbon dioxide (CO2) mobility during its injection in a porous media from pore scale to field scale. Therefore, enhancing in-situ CO2 foam propagation into sedimentary reservoirs is essential to maximize CO2 storage and EOR, and it may be achieved by adding polymers in the liquid lamellae.