Experimental investigation and optimization of polymer enhanced CO2 foam stability and apparent viscosity

Polymer enhanced foam (PEF) provides an additional strength over conventional CO2 foams for mobilizing oil from the unswept low permeable oil rich zones during an enhanced oil recovery process. The efficiency of the process depends on two major factors i.e. stability and apparent viscosity of PEF. In this study, an experimental investigation of apparent viscosity and stability of polymer enhanced CO2 foam is presented with an objective to assess the polymer performance and to identify the best performing polymer under reservoir conditions of 1500 psi and 80 °C. For this purpose, conventional standard hydrolyzed polymacrylamide (HPAM) polymers and an associative polymer i.e. Superpusher P329 were used in combination with a widely used foamer i.e. alpha olefin sulfonate (AOS) and a foam stabilizer i.e. betaine. Foam stability tests were conducted in the presence of crude oil using FoamScan. Whereas for foam rheological study, a high pressure high temperature Foam Rheometer was utilized and the foam was sheared over the range of 10 to 500 sec^-1 inside the recirculating loop. As compared to other HPAMs, an associative polymer i.e. Superpusher P329 significantly amplified foam longevity and provided a more prolonged liquid drainage. A shear thinning behavior was observed for the entire range of shear rate tested and for all the tested foam. HPAMs were found ineffective in improving foam apparent viscosity and the viscosities obtained were found equivalent to that to polymer free foam. Superpusher P329 showed interesting combination with AOS and significant viscosity enhancement has been reported in this paper. This research concluded that Superpusher P329 has the ability to generate strong foam and it is a potiential candidate for mobility control during polymer enhanced CO2 foam flooding process. Keywords: Polymer Enhanced Foam, foam stability, apparent viscosity; CO2 foam.