Experimental investigation and modelling of CO2‐foam flow in heavy oil systems

摘要

> In this work, the C _14‐16 alpha olefin sulphonate (AOS) surfactant, octylphenol ethoxylate (TX‐100), and methyl bis[Ethyl(Tallowate)]‐2‐hydroxyethyl ammonium methyl sulphate (VT‐90) surfactant were selected as representatives of anionic, nonionic, and cationic surfactant to stabilize foam. The effects of surfactant concentration and gas/liquid injection rates on foam performance were examined by performing a series of oil‐free foam flow tests by injecting CO ₂ and a foaming surfactant simultaneously into sandpacks. Foam flooding was conducted as a tertiary enhanced oil recovery (EOR) method after conventional water flooding and surfactant flooding. Furthermore, a new method was proposed to determine the residual oil saturation. The foam stability in the presence and absence of heavy oil was studied by a comparative evaluation of the mobility reduction factor ( F _MR ) in both cases. The foam fractional flow modelling by Dholkawala and Sarma [36] was modified based on experimental results obtained in this study. The range of the ratio of two important model parameters ( C _g /C _c ) at various foam qualities was determined and could be used for large‐scale predictions. The results showed that during the oil‐free foam displacement experiments higher foam apparent viscosities ( μ app ) were attained at lower gas flow rates and the maximum was attained at a total gas and liquid injection rate of 0.25?cm 3 /min with a gas fractional flow ratio of 0.8 for the foam in the absence of oil. The presence of oil reduced the foam mobility reduction factors ( F _MR ) to different degrees with F _MR ‐ _{without oil} / F _MR ‐ _{with oil} ranging from 4.25–13.69, indicating that the oil had a detrimental effect on the foam texture. The foam flooding successfully produced an additional 8.1–21.52??% of OOIP, which can be attributed to the combined effect of increasing the pressure gradient and oil transporting mechanisms.