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Research paper

The synergetic effect between heavy oil components and emulsifier in heavy

oil-in-water emulsion

Jinmei Bai a,, Tongyao Zhang b, Weiyu Fan c

a E-tech Oilfield Technology Development Co., Ltd. Tianjin, 300384, Chinab Institute of Oil Recovery Engineering CNOOC, Tanggu, Tianjin, 300452, Chinac State Key Laboratory of Heavy Oil Processing in China University of Petroleum, Shandong, 257061, China

a b s t r a c ta r t i c l e i n f o

Article history:Received 24 December 2007

Accepted 10 August 2009

Keywords:

heavy oil components

emulsifiers

interaction

pH value

interfacial tension

Resin and asphaltene were extracted from Gudao and Liaohe heavy oil by using the adsorptionchromatography. Toluene and n-dodecane were selected as model oil, sodium dodecylbenzene sulfonate

was selected as emulsifier. The interfacial tension (IFT) was investigated without emulsifier and adding

emulsifier, the effect of pH value on the interfacial tension was also investigated. The results show that the

interaction between component and emulsifier lies on the interfacial activity of components, and the higher

interfacial activity is, the stronger interaction is. And the influence of pH on IFT is great at acid and base

conditions, but little at neutral condition. The synergetic effect between polar component and emulsifier is

stronger in the neutral condition and weak acid and base conditions.

Crown Copyright 2009 Published by Elsevier B.V. All rights reserved.

1. Introduction

Emulsificationviscosityreduction is an important area of exploi-

tation, pipeline transportation and processing of heavy oil. Research-

ers have studied the preparation and application of heavy oil-in-water

emulsion (Zaki, 1997; Ahmed and Amal, 1999), but they did little

research about the mechanism of emulsification and stabilization of

heavy oil-in-water emulsion (Fan et al., 2001). They were only

interested in the stability of heavy oil emulsion (McLean and

Kilpatrick, 1997; Yang and Lu, 1998; Li, 1998). In order to widely

apply emulsificationviscosityreduction technology, research about

the mechanism of emulsification and stabilization of heavy oil-in-

water emulsion should be studied in-depth. The bad adaptability of

emulsifiers and the unmanageable stabilization were caused by the

differences of heavy oil components. The interaction between heavy

oil components and emulsifiers is the core of heavy oil-in-water

emulsion's formation and stabilization.In this paper, resin and asphaltene was extracted from Gudao and

Liaohe heavy oil with the method of adsorption chromatography.

Toluene and n-dodecane were selected as model oil, sodium

dodecylbenzene sulfonate(LAS) was selected as emulsifier. The

interfacial tension was investigated. When emulsifier was added

and before it was added, the effect of pH value on the interfacial

tension was investigated separately.

2. Experimental

Table 1 gives basic properties of Liaohe Du-84 heavy oil and

Shengli Gudao heavy oil.

Isolate heavy oil to polar components: the method to obtain polar

components (saturate, aromatic, resinand asphaltene) is based on the

Chinese petroleum industry standard method (SH/T 0509-92).The

main conditions are as follows:

Isolation of asphaltene: heavy oil:n-heptane= 1 g:50 mL; isolation

of soluble fractions: 75150 m neutral Al2O3 columns.

Acid number: using 0.1 M KOH/ethanol as titrant, V(toluene):V

(hexamethylene):V(anhydrous ethanol):V(water) = 100:50:49:1

as titration solvent, pHS-3C pH value meter.

Base nitrogen number: using perchloric acid/caproic acid as titrant,

V(toluene):V(caproic acid)= 10:20 as titration solvent, then

determining variation of electric potential (mV) with the volume

of titrant (V), the point whose derivatives are the largest on the

graph of mV versus V is the terminal point of titration.

Ultimate analysis: Elementar Analy Sensysteme GmbH Vario Elc III

ultimate analysis instrument (German).

Determination of interfacial tension: interfacial tension of oil

water is measured by spinning drop method at 50 C, using XZD-3

interfacial tension apparatus.

Preparation of oil/water system: heavy oil, resin and asphaltene

were regarded as solute; toluene and n-dodecane (W(toluene):W

(n-dodecane)= 1:1) were selected as mix solvent, a series of model

Journal of Petroleum Science and Engineering 69 (2009) 189192

Corresponding author.

E-mail address: baijinmei_1982@hotmail.com(J. Bai).

0920-4105/$ see front matter. Crown Copyright 2009 Published by Elsevier B.V. All rights reserved.

doi:10.1016/j.petrol.2009.08.008

Contents lists available at ScienceDirect

Journal of Petroleum Science and Engineering

j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / p e t r o l

mailto:baijinmei_1982@hotmail.comhttp://dx.doi.org/10.1016/j.petrol.2009.08.008http://www.sciencedirect.com/science/journal/09204105http://www.sciencedirect.com/science/journal/09204105http://dx.doi.org/10.1016/j.petrol.2009.08.008mailto:baijinmei_1982@hotmail.com

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oil containing 0.55% (w/w) solute were prepared. Sodium

dodecylbenzene sulfonate was selected as emulsifier. According to

the experimental demand, the variational aqueous phase was de-

ionized water, de-ionized water in different pH value, or emulsifier

aqueous solution.

3. Results and discussion

3.1. Elemental properties of two kinds of heavy oil and their polar

components

The elemental properties of two kinds of heavy oil and their polar

components as shown in Table 2 can reveal the following results:

The sequence of fractions content is: resin>aromatic>saturate>

asphaltene. Compared with Gudao heavy oil, there are more resins

and less asphaltenes in Liaohe heavy oil.

The acid number of two kinds of heavy oil and their fractions

suggests that they are different in the distribution of acid number

and the composition of acidic substance. The nitrogen number of

two kinds of heavy oil and their fractions indicates that they are

different in the composition of basic nitride.

The results of ultimate analysis got the conclusion that: compared

with Gudao heavy oil and its corresponding components, the

Liaohe heavy oil and its polar components have higher degree of

unsaturation, higher content of nitrogen and oxygen, and higheracid number. And most of nitrogen and oxygen atoms consist in

resin and asphaltene.

Basic properties showed that there are more differences between

two kinds of heavy oil and their polar components, which make it

easyto reviewthe influence of component difference on interfacial

property in the study.

3.2. Comparison of interfacial activities of two kinds of heavy oil and

their polar components

Interfacial tension is the most important parameter of oil water

interfacial property. It affects the adsorption rata and adsorbed

amount of polar components in oil/waterinterface and also affects the

interfacial structure. It is the appearance of interaction between polar

components and emulsifier.

In order to compare two kinds of heavy oil and their polar

components' interfacial activity, the influence of dosage of heavy oil

and its polar components in simulated oil on oil water interfacial

tension was studied. Table 3 shows the results.

Blank interfacial tension is the oil/water interfacial tension of

blank model oil and de-ionized water without components. The dataofTable 3 show that the existence of heavy oil and polar components

reduce the oil/water interfacial tension of model oil, and the tendency

of oil/water interfacial tension reduces with the increasing of polar

components' contents. Results indicate that the adsorbed amount of

natural surfactant existing in crude oilincreases with theincreasing of

polar components' contents, it goes into saturation under certain

concentrations. Interfacial pressure is the variation of the oil/water

interfacial tension with and without surfactant.

=

is the symbol for interfacial pressure, stands for the oil/water

interfacial tension without surfactant, stands for the oil/water

interfacial tension with surfactant. Interfacial pressure is the symbol

of interfacial activity. Interfacial pressure increases with the adsorbate

amount of surfactant in surface. The larger interfacial pressure in the

same concentration, the stronger the ability of reducing interfacial

tension will be.

Table 4 gives the influences of heavy oil and its components

amount in model oil on oilwater interfacial pressure. The data of

Table 4 show that theinterfacialpressureof two kinds of heavy oil and

their polar components are different in the same concentration, that

is, their interfacial activities are different. The sequence of the

interfacial activity (IFA) of Gudao heavy oil and its polar components

is IFA (heavy oil)>IFA(resin)>IFA (asphaltene). The sequence of the

IFA of Liaohe heavy oil and its polar components is IFA (asphaltene)>

IFA(heavy oil)> IFA (resin). The interfacial activity of Liaohe heavy oil

and its polar fractions is superior to that of Gudao.

From elemental properties and the IR spectrum of asphaltene, wecan know there are hydroxide radical, amidocyanogen, carbonyl

group and carboxyl in asphaltene molecule, and Liaohe asphaltenehas

more than others, so there is more hydrogen bond in asphaltene

which leads to stronger interfacial activity of asphaltene (Fig. 1).

3.3. Effects of the interaction of heavy oil components and emulsifiers on

interfacial tension

In order to review the influences of the interaction between

components and emulsifier on interfacial tension, the variation of

interfacial tension with the concentration of fractions in the model oil

with 1% emulsifier was studied. Table 5 gives the results.

Table 2

Elemental properties of two kinds of heavy oil and their polar components.

Heavy o il f ractions Dist ribution/% Acid

number/mg

KOH g1

Nitrogen

number/g g1Element fractions/% n(H)/n(C)

C H N O S

Gudao heavy oil 3.25 13441 84.01 10.92 0.57 0.64 3.31 1.56

Liaohe heavy oil 9.05 8106 86.50 10.91 0.81 1.33 0.42 1.51

Gudao saturates 25.08 86.73 13.12 0 0 0 1.82

Liaohe saturates 26.07 87.07 12.87 0 0 0 1.77

Gudao aromatics 31.39 84.25 10.70 0.24 0.19 4.16 1.52

Liaohe aromatics 28.49 87.87 10.57 0.34 0.19 4.16 1.44

Gudao resins 34.88 0.23 13671 82.97 9.85 1.39 1.40 3.99 1.42

Liaohe resins 41.65 0.22 13149 85.53 9.93 1.74 1.57 0.55 1.39

Gudao asphaltenes 6.65 2.79 13212 80.62 8.72 1.21 1.96 6.37 1.30

Liaohe asphaltenes 3.38 9.74 20830 81.92 8.65 1.71 3.13 0.51 1.26

The amount of resins is calculated according to difference; the amount of oxygen is the actual value examined.

Table 1

Basic properties of Liaohe and Gudao heavy oil.

Heavy oil Density (20 C)/

(g cm3)

Viscosity (80 C)

/(mm2 s1)

Solidification

point/ C

Acid number/

mg KOH g1

Gudao 0.9934 810.38 8.5 3.25

LiaoheDu-84 1.0001 4898.92 42 9.05

Gudao is a production base of heavy oil in Shengli Oilfield which is the second oilfield

of China.

Liaohe Oil field is the third oil field of China, most of its reserve is heavy oil.

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Blank interfacial tension is the interfacial tension of blank model

oil and 0.1% LAS water solution without components. In order to

compare the effect of the interaction between fractionsand emulsifier

on interfacial tension, the difference of after and before adding

components in fixed concentration of emulsifier as a parameter was

made which is similar to interfacial pressure, and marked as .

Table 6 gives the variation of under different concentrations of

fractions.

The results ofTable 5 as follows: after the addition of heavy oil and

polar component, the interfacial tension is lower than the blank. The

fact indicates the interaction between natural surfactants in heavy oil

and emulsifier reduces the interfacial tension.The data of Table 6 reveal that the interaction between different

fractionsand emulsifier did different effects on interfacial tension. The

large interfacial activity fraction Liaohe asphalteneshows stronger co-

operation. But the Gudao asphaltene and Liaohe resin of weak

interfacial activity did little on the interfacial tension, this fact

indicates that there wasn't distinct co-operation between them and

emulsifier.

All in all, the interaction between heavy oil component and

emulsifier depends on the interfacial activity of heavy oil and its

components, the more active of component, the higher interaction

it is.

3.4. Effect of pH value on interfacial tension of simulated oil system

Aqueous phase is one of the dominant factors of emulsion's

interfacial property. The effects of pH value on interaction between

fractions and emulsifier have been studied. The data of Figs. 25

indicate the effects of pH value of aqueous on interfacial tension.

We canobtain regularity from Figs. 2 and 3 that before being added

emulsifier, the IFT of the two kinds of heavy oil and its polar

components simulated oil and de-ionized water vary as follows.When it is pH< 7, the interfacial tension increases with the increasing

of pH value. When it is pH> 7, the interfacial tension beginsto reduce;

the interfacial tension at the basic condition is lower than that in the

acidic condition. The results above show that the interfacial activity of

heavy oil and its polar fraction is great at basic conditions.

The interfacial tension of model oil system changed with pH value

after being added 1% emulsifier. The results are shown in Figs. 4 and 5.

We can know from Figs. 3 and 4 that after being added 1%

emulsifier, the interfacial tension of the blank model oil is lower in the

Table 3

The influences of heavy oil and its components amount in model oil on oil water

interfacial tension.

Model oil /mNm1

Blank 0.5% 1.0% 2.0% 3.0% 4.0% 5.0%

Gudao heavy oil 41.45 26.84 25.44 24.44 24.06 23. 63 23.02

Gudao resins 41.45 34.96 34.58 31. 90 27.35 26. 89 25.14

Gudao asphalten es 41.45 35.30 34.91 32.85 31.02 29.55 27.57

Liaohe he avy oil 41.45 22.82 21.74 17.84 17.08 16.17 14.95

Liaohe resins 41.45 39.54 32.22 31.91 25.37 23. 79 23.65

Liaohe asphaltenes 41.45 9.96 8.15 8.13 8.01 7.94 7.32

Table 4

The influences of heavy oil and its components amount in model oil on oilwater

interfacial pressure.

Model oil /mNm1

Blank 0.5% 1.0% 2.0% 3.0% 4.0% 5.0%

Gudao heavy oil 0 14.61 16.01 17.01 17.39 17.82 18.43

Gudao resins 0 6.49 6.87 9.55 14.10 14.56 16.31

Gudao asphaltenes 0 6.15 6.54 8.60 10.43 11.90 13.88

Liaohe heavy oil 0 18.63 19.71 23.61 24.37 25.28 26.50

Liaohe resins 0 1.91 9.23 9.54 16.08 17.66 17.80

Liaohe as phaltenes 0 31.49 33.30 33.32 33.44 33. 51 34.13

Fig. 1. IR spectrum of Gudao and Liaohe asphaltene.

Table 5

The variation of interfacial tension with the concentration of fractions in the model oil

(with 1% emulsifier).

Model oil /mNm1

Blank 0.5% 1.0% 2.0% 3.0% 4.0% 5.0%

Gudao heavy oil 3.28 2.85 2.55 2.34 2.44 2.43 2.40

Gudao resins 3.28 3.33 2.93 2.74 2.82 2.95 2.89

Gudao asphaltenes 3.28 3.41 3.22 3.34 3.06 3.16 3.02

Liaohe heavy oil 3.28 2.79 2.62 1.95 1.94 1.93 1.95

Liaohe resins 3.28 3.08 3.31 3.16 3.67 3.26 3.62

Liaohe asphaltenes 3.28 1.30 0.70 0.25 0.29 0.35 0.35

Table 6

The variation of interfacial tension difference with the concentration of fractions in the

model oil (with 1% LAS).

Model oil /mNm1

Blank 0.5% 1.0% 2.0% 3.0% 4.0% 5.0%

Gudao heavy oil 0 0.43 0.73 0.94 0.84 0.85 0.88

Gudao resin 0 0.05 0.35 0.54 0.46 0.33 0.39

Gudao asphaltene 0 0.13 0.06 0.06 0.22 0.12 0.26

Liaohe heavy oil 0 0.49 0.66 1.33 1.34 1.35 1.33

Liaohe resin 0 0.20 0.04 0.12 0.40 0.02 0.34

Liaohe asphaltene 0

1.98

2.58

3.03

2.99

2.93

2.93

Fig. 2. The influences of pH value on IFT of Gudao heavy oil and its polar components

model oil/de-ionized water. (1) 5% Gudao asphaltenes model oil, (2) 5% Gudao heavy

crude model oil and (3) 5% Gudao resins model oil.

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strong acidic and strong basic conditions, and it is even lower in the

strong acidic condition, but the adding of heavy oil and their polar

components doesn't change their interfacial tension much. That is,

there is no distinct interaction between emulsifier and components in

the strong acidic and basic conditions. In the neutral and weak acidic

and basic conditions with a pH value from 4 to 10, the adding of heavy

oil and its polar components lowers the interfacial tension obviously

and shows distinct interaction. This fact indicates that the influence of

pH is great at neutral, weak acidic and basic conditions, but little at

strong acidic and basic conditions.

The interfacial activity of emulsifier is stronger than that of heavy

oil and its polar fractions, the strong acidic and basic conditions cover

up components' interfacial activity, but the stronger Liaohe heavy oil

and its asphaltene show interaction in some way. Comparatively, the

emulsifier's adsorptive capacity in interface reduces in theneutral and

weak acidic and basic conditions, and the heavy oil and its polar

components adsorb competitively in interface, co-operate with

emulsifier, and they reduce the interfacial tension together. This fact

attests that there is large interaction between heavy oil and its polarfraction and emulsifier in the neutral and weak acidic and basic

condition.

4. Conclusion

(1) Compared with Gudao heavy oil and its corresponding compo-

nents, the Liaohe heavy oil and its polar components havehigher

degree of unsaturation, higher content of nitrogen and oxygen,

higher acid number and relatively stronger interfacial activity.

(2) Liaohe asphaltene, which has a stronger interfacial activity, can

reduce the oilwater IFT, shows a stronger synergetic effect with

emulsifier; Gudao asphaltene and Liaohe resin, which have a

weaker interfacial activity, do not show any clear synergetic

effect with emulsifier. The interaction between polar component

of heavy oil and emulsifier lies on the interfacial activity of polar

component: the stronger interfacial activity of component, the

stronger interaction it is.

(3) In the strong acidic and basic conditions, there is no distinct

synergetic effect between emulsifier and components; In the

neutral and weak acidic and basic conditions with a pH value

from 4 to 10, the IFT reduces obviously with the adding of heavy

oil and its polar components, and shows stronger synergetic

effect. This fact approves that there is interaction between heavy

oil and its polar components and emulsifier.

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Fig. 3. The influences of pH value on interfacial tension of Liaohe heavy oil and its polar

components model oil-de-ionized water. (1) 5% Liaohe resins model oil, (2) 5% Liaohe

heavy crude model oil and (3) 5% Liaohe asphaltenes model oil.

Fig. 4. The influences of pH value on IFT of Gudao heavy oil and its polar components

model oil and 1% emulsifier in water. (1) blank model oil, (2) 5% Gudao asphaltenes

model oil, (3) 5% Gudao heavy model oil and (4)5% Gudao resins model oil.

Fig. 5. The influences of pH value on interfacial tension of Liaohe heavy oil and its polar

components model oil and 1% emulsifier in water. (1) 5% Liaohe resins model oil,

(2) blank model oil, (3) 5% Liaohe heavy crude model oil and (4) 5% Liaohe asphaltenes

model oil.

192 J. Bai et al. / Journal of Petroleum Science and Engineering 69 (2009) 189192