Correlation between phase behavior and IFT

Leslie Zhang

Phase behavior after 2 months with 0.2% (left) and

0.5% (right) NI blend.

x= 2.0 3.0 3.2 3.4 3.6 3.8 4.0

0.2% NI blend/1% Na2CO3/x% NaCl @ soap/synthetic surfactant ratio of 0.35 (WOR=3:1)

2 months settling at room temperature

0.5% NI blend/1% Na2CO3/x% NaCl @ soap/synthetic surfactant ratio of 0.14 (WOR=3:1)

2 months settling at room temperature

x= 3.0 3.5 4.0 4.3 4.5 4.7 5.0x= 2.0 3.0 3.2 3.4 3.6 3.8 4.0

0.2% NI blend/1% Na2CO3/x% NaCl @ soap/synthetic surfactant ratio of 0.35 (WOR=3:1)

2 months settling at room temperature

0.5% NI blend/1% Na2CO3/x% NaCl @ soap/synthetic surfactant ratio of 0.14 (WOR=3:1)

2 months settling at room temperature

x= 3.0 3.5 4.0 4.3 4.5 4.7 5.0

Solubility ratios of 0.2% NI blend /

1% Na2CO3 / NaCl

1

10

100

1000

2 2.5 3 3.5 4

NaCl, %

Sol

ubi

lity

rat

io

Vw/ Vs

Vo/Vs

1

10

100

1000

2 2.5 3 3.5 4

NaCl, %

Sol

ubi

lity

rat

io

1

10

100

1000

2 2.5 3 3.5 4

NaCl, %

Sol

ubi

lity

rat

io

Vw/ Vs

Vo/Vs

Huh Correlation, 1979

23

3

l

lR

c

interfacial tension between excess oil or aqueous phase and middle phase,

Rl3: solubility ratio of oil or water by surfactant

c: a constant with a typical value of 0.3.

3

Comparison of IFT measured by spinning drop measurements using standard procedure and that estimated by Chun-Huh

correlation of 0.2% NI blend/1% Na2CO3/NaCl. c=0.3.

Solubility ratios of 0.5% NI blend / 1% Na2CO3 / NaCl

1

10

100

1000

3 3.5 4 4.5 5

NaCl, %

Sol

ubi

lity

rat

io

Vw/ Vs

Vo/Vs

1

10

100

1000

3 3.5 4 4.5 5

NaCl, %

Sol

ubi

lity

rat

io

1

10

100

1000

3 3.5 4 4.5 5

NaCl, %

Sol

ubi

lity

rat

io

Vw/ Vs

Vo/Vs

IFT estimated by Chun-Huh correlation of 0.5% NI blend/1% Na2CO3/NaCl, c=0.3.

0.0001

0.001

0.01

0.1

3 3.5 4 4.5 5

NaCl, %

IFT

, mN

/m

Chun-Huh correlation

0.0001

0.001

0.01

0.1

3 3.5 4 4.5 5

NaCl, %

IFT

, mN

/m

Chun-Huh correlation

Phase behavior of 0.2% NI blend/1% Na2CO3/x% NaCl, 40 days of settling.

Thin creamed oil-rich layers exist at salinity of 2-3.4% NaCl. S/SR=1

x= 2.0 2.0 3.0 3.2 3.4 3.6 3.8 4.0

Soap / Synthetic surfactant ratio = 0.35S/SR=1

x= 2.0 2.0 3.0 3.2 3.4 3.6 3.8 4.0

Soap / Synthetic surfactant ratio = 0.35

x= 2.0 2.0 3.0 3.2 3.4 3.6 3.8 4.0

Soap / Synthetic surfactant ratio = 0.35

Conclusions

• The measured low IFT over a wide range of salinity is consistent with the solubility ratio data.

• The thin layer of oil-rich emulsion may be responsible for the above observation.

• The dependence of this layer on the amount of oil present suggests that it may be due to the presence of the naphthenic soaps.