Tab. 1

Composition of the formation water from the oil field"

Fig. 1

Photos of emulsions of petroleum sulfonate/simulated crude oil/simulated formation water. They are grouped in four sets （labelled as “A”, “B”, “C” and “D”, respectively）. The mass concentrations of petroleum sulfonate solutions are （A） 1 000 mg/L, （B） 3 000 mg/L, （C） 5 000 mg/L and （D） 6 000 mg/L, respectively. The oil-water ratios for the six samples in each set are 2:8, 3:7, 4:6, 5:5, 6:4 and 7:3 （from left to right）"

Fig. 2

Microstructure of the emulsions with 1 000 mg/L petroleum sulfonate solution at different oil-water ratios"

Fig. 3

Microstructure of the emulsions with 5 000 mg/L petroleum sulfonate solution at different oil-water ratios"

Fig. 4

Microstructure of the emulsions with oil-water ratios of 4:6 （the top row） and 6:4 （the bottom row）. The mass concentrations of petroleum sulfonate solutions are （A） 1 000 mg/L, （B） 3 000 mg/L, （C） 5 000 mg/L and （D） 6 000 mg/L, respectively"

Fig. 5

Plot of interfacial tension at different mass concentrations of petroleum sulfonate in formation water against simulated crude oil"

Fig. 6

Phase diagram of petroleum sulfonate solution/simulated crude oil at （65±1） ℃. The mineralization degree of the solution is 30 000 mg/L"

Fig. 7

Mean particle size of emulsions at different oil-water ratios. The mass concentrations of petroleum sulfonate solutions are 1 000, 3 000, 5 000 and 6 000 mg/L, respectively"

Fig. 8

Water separation in the emulsions of petroleum sulfonate/simulated crude oil/simulated formation water after standing for 60 min. The samples are grouped in four sets （labelled as “A”, “B”, “C” and “D”, respectively）. The mass concentrations of petroleum sulfonate solutions are （A） 1 000 mg/L, （B） 3 000 mg/L, （C） 5 000 mg/L and （D） 6 000 mg/L, respectively. The oil-water ratios for the six samples in each set are 2:8, 3:7, 4:6, 5:5, 6:4 and 7:3 （from left to right）"

Fig. 9

Variation of water separation percent （a） and emulsion separation index （b） with oil-water ratio for the emulsions containing different mass concentrations of petroleum sulfonate"

Fig. 10

Dynamic interfacial tension curves between petroleum sulfonate solution and simulated crude oil at different temperatures"

Fig. 11

Variation of interfacial dilational viscoelastic modulus between petroleum sulfonate solution and simulated crude oil with time at different temperatures"

Fig. 12

Microstructure of emulsions at different temperatures: （A） 25 ℃, （B） 65 ℃, （C） 80 ℃. The oil-water ratio is 5:5. The mass concentrations of petroleum sulfonate solutions are 1 000, 3 000, 5 000 and 6 000 mg/L, respectively"

Fig. 13

Mean particle size of emulsions at different temperatures. The oil-water ratio is 5:5. The mass concentrations of petroleum sulfonate solutions are 1 000, 3 000, 5 000 and 6 000 mg/L, respectively"

Fig. 14

Water separation percent （a） and emulsion separation index （b） of emulsions at different temperatures. The oil-water ratio is 5:5"

Fig. 15

Dynamic interfacial tension curves between petroleum sulfonate solution and simulated crude oil at different mineralization degrees"

Fig. 16

Microstructure of emulsions at different mineralization degrees: （A） 0 mg/L, （B） 30 000 mg/L, （C） 90 000 mg/L. The oil-water ratio is 5:5. The mass concentrations of petroleum sulfonate solutions are 1 000, 3 000, 5 000 and 6 000 mg/L, respectively"

Fig. 17

Mean particle size of emulsions at different mineralization degrees. The oil-water ratio is 5:5"

Fig. 18

Water separation percent （a） and emulsion separation index （b） of emulsions at different mineralization degrees. The mass concentrations of petroleum sulfonate solutions are 1 000, 3 000, 5 000 and 6 000 mg/L, respectively"

Fig. 19

Viscosity of the emulsions at different oil-water ratios. The mass concentration of petroleum sulfonate solution is 1 000 mg/L"