The surface and interfacial tensions without alkali between Daqing crude oil and homemade carboxyl betaine(BC)containing double bond were studied.The critical micelle concentration(C_(cmc)) of BC was 1.02×10~(-5) mol/L,and γ_(cmc) was 29.603 mN/m at 45℃.When oil and produced water source was the first oil production factory in Daqing,the interfacial tension between BC surfactant solution or BC/0.09%HPAM binary solution with BC concentration of 0.05%—0.20%and crude oil or simulated crude oil reached ultralow...