Study on enhanced oil recovery by multi-component foam flooding

Abstract

To obtain a foam system with better stability and oil resistance, this paper starts with the mechanism of enhanced oil recovery by foam flooding and makes use of a combination of surfactants to make foam more stable. A foam system with strong stability can be obtained by combining anionic surfactants with nonionic surfactants. Based on this idea, a new type of multi-component foam flooding system (system 1) is developed. The main molecule is zwitterionic surfactant with a concentration of 0.7% fourteen alkyl sulfonated fluorobetaine (SFN). The auxiliary surfactants are present at a concentration of 0.3% of Sodium Dodecyl Sulfate (SDS), a concentration of 1.8% of potassium chloride (KCL) and a concentration of 3.0% of anhydrous ethanol (C2H6O). In addition, adding a 1000 mg/L solution of partially hydrolyzed polyacrylamide (HPAM) into the system can enhance the strength of the interfacial film, increase the surface dilatation modulus and extend the equilibration time, thereby enhancing the stability of the foam. The comparative evaluation experiment results show that the foaming capacity, foam stability and comprehensive performance of system 1 are better than those of other common foam systems under the condition of 30% Sor and a 1:1 ratio of gas to liquid. For system 1, the number of bubble films L (lamella number) is less than 7, the boundary between the foam and crude oil is clear, and the interaction is small. The foam of system 1 has good oil resistance. The results of oil displacement show that the oil recovery using system 1 increases by 16.8 percentage points after polymer flooding, which is 4–6 percentage points higher than that of an ordinary foam system. The results of the oilfield test show that the development effect of polymer flooding in the B block is poor. In January 2017, system 1 was injected into the reservoir. The 23 wells in the B block responded well, and the effective ratio reached 92%. Compared with the previous stage, the daily fluid production increased by 215 m3, the daily oil production increased by 141.0 t, the water cut decreased by 9.2 percentage points, and the reservoir effect was obvious. This result provides a new idea for the later development of high water cut reservoirs.