Asghar Gandomkar, Farshid Torabi
Summary Minimum miscibility pressure (MMP) is one of the main technical challenges during carbon dioxide (CO2) flooding. Therefore, in this work, we explore the effect of small-molecule CO2-soluble polymers, including poly(dimethyl siloxane) (PDMS), poly(fluoroacrylate) (PFA), poly(1-decane) (P-1-D), and poly(vinyl ethyl ether) (PVEE), on MMP during gasflooding. Different concentrations of polymers (1,000–50,000 ppm) were considered to dissolve in CO2 at 60°C and 80°C. According to the cloudpoint pressure (CPP) results, the small-molecule CO2-soluble polymers dissolved in CO2 at pressure commensurate with CO2-enhanced oil recovery (EOR) (less than 2,500 psi) at both 60°C and 80°C. Also, the dissolution of the small-molecule gas-soluble polymers in CO2 results in increasing the CO2/polymer solutions’ densities and led to extremely reduced (CO2/polymers)-oil interfacial tensions (IFTs). Moreover, the MMPs decreased significantly by 19.4% for CO2/PFA, 17% for CO2/PDMS, 13.6% for CO2/PVEE, and 10% for CO2/P-1-D scenarios compared with pure CO2 scenario. In addition, the tertiary oil recovery factors were 88.7% (at stabilized pressure gradient of 80.3 psi/ft) and 62.2% (at stabilized pressure gradient of 72 psi/ft) of original oil in place (OOIP) during the miscible CO2/PDMS and pure CO2 injection scenarios, respectively. Therefore, the small-molecule CO2-soluble polymers containing functional groups with oxygen can be one of the most promising candidates for miscible CO2 displacement on the field scale, but the economic concerns, long-term sustainment of miscibility, and field-relevant flux rate (for both low and high permeability) need to be further investigated.