Abstract:In view of the practical problems of existing commercial foams in high temprature, high salinity and low permeability reservoirs, such as low foaming volume, poor foam stability in porous media, and low oil displacement efficiency, two kinds of asymmetric amphoteric Gemini Surfactants (PAHC and PAOC) were synthesized by etherification, quaternization, and substitution reactions as foaming agents for CO2 foam flooding, and the structure of the products was determined by IR and NMR. The CMC of PAHC and PAOC were 6.76 × 10-5 mol/L and 5.25 × 10-5 mol/L, respectively, and the corresponding surface tension γ CMC were 31.56 mN/m and 30.71 mN/m, respectively, and their Krafft points wete >0 ℃ and >1 ℃, respectively, which shows that the two surfactants had good surface properties. Under the conditions of reservoir temperature and salinity of Gao 21-3 well in the Second Oil Production Plant of Jiangsu Oilfield, the performance of two foaming agent systems with two asymmetric amphoteric Gemini surfactants as the main foaming agent were evaluated. The results show that at a constant shear rate of 170 s-1, the temperature resistance of PAHC-C16S and PAOC -C18S foaming systems were 81 ℃ and 88 ℃, respectively, and the viscosity of the two systems can be maintained at 6.2 MPa. s and 6.4 MPa. s, respectively, which showed their had good injection, and the viscoelastic properties of the two foaming systems were also good. The two foaming systems PAHC -C16S and PAOC -C18S could reduce the oil-water interfacial tension to 2.37×10-2 mN/m and 1.81×10-2 mN/m, respectively. The two foams, PAHC-C16S and PAOC-C18S, had good temperature and salt resistance, but the temperature and salt resistance of PAOC -C18S’s foam is slightly better than that of PAHC-C16S’s foam, which can be used in CO2 foam flooding in high temperature and high salinity reservoirs such as Gao 21-3 well in the Second Oil Production Plant of Jiangsu Oilfield. The core oil displacement experiment results show that the average EORs of PAHC-C16S and PAOC-C18S foam systems on the basis of CO2 flooding were 20.12% and 21.91% respectively, which showed that both kinds of foam had good recovery effect.