CO2 mobility control by small molecule thickeners during secondary and tertiary enhanced oil recovery

Abstract Recently, polymer thickeners have been considered for CO 2 mobility control during enhanced oil recovery (EOR) processes. Despite that, the requirement of co‐solvents is a controversial challenge for the solution of high‐molecular weight thickeners in gases. This study is focused on small molecule thickeners for carbon dioxide EOR without adding co‐solvents. Polydimethylsiloxane (PDMS) was used as a CO 2 ‐philic thickener in different low molecular weights. Cloud‐point pressure, relative viscosity, and interfacial tension (IFT) between intermediate crude oil and pure/thickened CO 2 were measured at reservoir conditions. Also, the impact of PDMS‐CO 2 thickener on gas mobility control was evaluated during the coreflooding experiments in secondary and tertiary modes. The experimental results show that PDMS caused an increase in relative viscosity up to 4.7‐fold and successfully thickened CO 2 . In addition, the minimum miscibility pressure of PDMS‐thickened CO 2 was lower than that of pure CO 2 , and miscible PDMS‐CO 2 thickener occurred at higher PDMS molecular weights. However, the gas breakthrough time can be considerably delayed if the PDMS‐thickened CO 2 was flooded directly, which increased the oil recovery factor between 6% to 15% during tertiary recovery.