Group Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings
Title: P3.77 - Investigation on heavy crude oil-water two phase flow and related flow characteristics
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 Material Information
Title: P3.77 - Investigation on heavy crude oil-water two phase flow and related flow characteristics
Series Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings
Physical Description: Conference Papers
Creator: Wang, W.
Gong, J.
Shi, B.
Shuai, H.
Publisher: International Conference on Multiphase Flow (ICMF)
Publication Date: June 4, 2010
 Subjects
Subject: heavy crude oil-water
two phase flow
w/o emulsion
phase inversion
natural surfactants
 Notes
Abstract: In petroleum industry, it’s a common phenomenon that crude oil and water two phases flow together during drilling and transporting process. Since crude oil usually contains natural surfactants as asphaltene, resin and small particles, it’s easier to form water-in-crude oil emulsion. Thus their flowing characters would be much more complex due to the effect of emulsification. In china, heavy crude oils take a huge percentage of its total oil production, and the total mass fraction of asphaltene and resin may even higher to 20%. It’s found that crude oil and water phase easily joined together and formed stable water-in-oil (w/o) emulsion in the drilling and transportation pipeline. The apparent viscosity of the formed emulsion is greatly increased, while it shows a strong non-Newtonian characteristic with the increment of water fraction. Through the experiments of crude oil-water two-phase flow, flow characteristic as flow patterns, pressure drop gradient and phase inversion phenomenon are investigated. Result indicates that phase inversion phenomenon during crude oil-water flow is different from its theoretical definition which is defined as the transition from o/w to w/o. Instead, it’s obviously influenced by the emulsification of oil and water phase. Based on above understandings, it’s strongly recommended to further investigate the non-Newtonian properties of the formed w/o emulsion, which could help to gain more understandings on their pipe flow character.
General Note: The International Conference on Multiphase Flow (ICMF) first was held in Tsukuba, Japan in 1991 and the second ICMF took place in Kyoto, Japan in 1995. During this conference, it was decided to establish an International Governing Board which oversees the major aspects of the conference and makes decisions about future conference locations. Due to the great importance of the field, it was furthermore decided to hold the conference every three years successively in Asia including Australia, Europe including Africa, Russia and the Near East and America. Hence, ICMF 1998 was held in Lyon, France, ICMF 2001 in New Orleans, USA, ICMF 2004 in Yokohama, Japan, and ICMF 2007 in Leipzig, Germany. ICMF-2010 is devoted to all aspects of Multiphase Flow. Researchers from all over the world gathered in order to introduce their recent advances in the field and thereby promote the exchange of new ideas, results and techniques. The conference is a key event in Multiphase Flow and supports the advancement of science in this very important field. The major research topics relevant for the conference are as follows: Bio-Fluid Dynamics; Boiling; Bubbly Flows; Cavitation; Colloidal and Suspension Dynamics; Collision, Agglomeration and Breakup; Computational Techniques for Multiphase Flows; Droplet Flows; Environmental and Geophysical Flows; Experimental Methods for Multiphase Flows; Fluidized and Circulating Fluidized Beds; Fluid Structure Interactions; Granular Media; Industrial Applications; Instabilities; Interfacial Flows; Micro and Nano-Scale Multiphase Flows; Microgravity in Two-Phase Flow; Multiphase Flows with Heat and Mass Transfer; Non-Newtonian Multiphase Flows; Particle-Laden Flows; Particle, Bubble and Drop Dynamics; Reactive Multiphase Flows
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Volume ID: VID00547
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Holding Location: University of Florida
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Resource Identifier: P377-Wang-ICMF2010.pdf

Full Text

7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010


Investigation on heavy crude oil-water two phase flow and related flow characteristics


Wei Wang1'2, Jing Gong1, Bohui Shi1, Hao Shuai1


1 Beijing Key Laboratory of Urban Oil&Gas Distribution Technology, China University of Petroleum, Beijing, China
2 Post-Doctoral Research Center of China Petroleum Pipeline Bureau (CPPLB), CNPC, Langfang, China
E-mail: w.wang @cup.edu.cn

Keywords: heavy crude oil-water; two phase flow; w/o emulsion, phase inversion, natural surfactants

Abstract

In petroleum industry, it's a common phenomenon that crude oil and water two phases flow together during drilling and
transporting process. Since crude oil usually contains natural surfactants as asphaltene, resin and small particles, it's easier to
form water-in-crude oil emulsion. Thus their flowing characters would be much more complex due to the effect of
emulsification. In china, heavy crude oils take a huge percentage of its total oil production, and the total mass fraction of
asphaltene and resin may even higher to 20%. It's found that crude oil and water phase easily joined together and formed
stable water-in-oil (w/o) emulsion in the drilling and transportation pipeline. The apparent viscosity of the formed emulsion is
greatly increased, while it shows a strong non-Newtonian characteristic with the increment of water fraction.
Through the experiments of crude oil-water two-phase flow, flow characteristic as flow patterns, pressure drop gradient and
phase inversion phenomenon are investigated. Result indicates that phase inversion phenomenon during crude oil-water flow is
different from its theoretical definition which is defined as the transition from o/w to w/o. Instead, it's obviously influenced by
the emulsification of oil and water phase. Based on above understandings, it's strongly recommended to further investigate the
non-Newtonian properties of the formed w/o emulsion, which could help to gain more understandings on their pipe flow
character.


Nomenclature


Flows of mixtures of two immiscible fluids as oil and water
occur in many applications in the process industries, such as
two-phase reactors with immiscible liquid catalysts and in
the petroleum industry. It is this latter case that this paper is
concerned with. Researchers (Charles et al., 1961; Oglesby,
1979; Arirachakam et al., 1989; Trallero, 1996; Andreini et
al., 1997; Niidler &Mewes, 1997; Angeli&Hewitt, 2000; Shi,
a, b, 2001; Lovick&Angeli, 2004; Ioannou et al., 2005;
Janaa et al., 2006) have carried out numbers of investigation
on the oil-water flow regimes and transition characteristics,
related pressure drop and phase inversion phenomenon.
However, on account of the fact that most of the
experiments conducted are laboratory used mineral
oil-water two phase flow and the acquired theories may not
be fitted for crude oil-water flow. While with the fast
development of heavy crude oil offshore oilfield across the
world, it is therefore imperative for the heavy crude
oil-water two phase flow research to be taken into
consideration.
In this paper, heavy crude oil and water phases are put ahead
into a storage tank and mixed by a stirred mixer at the
rotation speed of 400rpm, and then they are pumped into the
flow loop for further investigations. This kind of procedure
intends to form oil and water emulsion before flowing into
the loop, which is actually occurred in the submarine
pipeline of the offshore oilfield. Flow regimes, transition
characteristics, pressure drop and phase inversion
phenomenon are investigated, while the non-Newtonian
properties of the formed w/o emulsion is also characterized,
with the purpose of guiding reference for the research and
oilfield applications in this field.


C
D
d
NI
n
dp/dl
V
We,
We,
Re


Parameter
Inner diameter of the pipe (m)
Drop diameter (m)
Impeller agitation speed (s1)
Parameter
Pressure drop gradient (KPa/m)
Velocity (m/s)
Weber number of the impeller
Weber number
Reynolds number


Greek letters
p Density (kg/m3)
P Viscosity (Pa-s)
0 Phase volume fraction
A Fraction factor
o Interfacial tension (N/m)

Subsripts
c Continuous phase
m Oil and water mixture
o Oil phase
w Water phase


Experimental Facility

Experiments are carried out in the Laboratory for
multiphase flow of the China University of Petroleum. The
experiment facilities are shown in Fig.l. It is a steel pipe
loop with an inner pipe diameter of 25.4 mm, consisting of a
pressure drop test section whose length is 2m. It's over


Introduction









20meters away from the pipe entrance, L/Dz790>> 200,
which indicates that the flow regimes of the oil-water two
phases have already been fully developed at the test section.
Differential pressure transducer is used, that sampled signals
with a frequency of 50 Hz. The flow rate measurements
made with flow meter were used to control screw pumps via
a feedback system. Behind the pressure drop test section, a
self-made local sampling device is developed and fixed,
which has been depicted by Wang&Gong (2009). Properties
of oil-water mixture can be investigated through local
sampling device, which can also measure the height of
oil-water interface during stratified flow.


1---Storage tank, 2---Water tank, 3---Little screw pump,
4---Big screw pump, 5---Pressure gauge, 6---Pressure drop
test section, 7---Transparent organic glass section, 8---Local
sampling device, 9---Centrifugal pump, 10---Ball valve,
11---Mass flow meter, 12---Inlet gas phase, 13---Quick
stroking valve, 14---Data acquisition system.
Figure 1: Sketch of the experimental facilities

Experiments is carried out at 60C, where oil and water
phases are put into a storage tank and mixed homogeneously
by a stirred mixer at the fixed rotation speed of 400rpm.
This mixing speed is elaborated selected at which the heavy
crude oil and water phase can be fully dispersed and the
physical characters of the formed emulsion are much
approximately as the oil-water mixture produced from the
oilfield drilling well. The property of heavy crude oil phase
is given in Table 1. Flow regimes, transition characters and
phase inversion phenomenon are carefully identified by
jointly using of local sampling methods and analysis of
pressure drop signals.


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

Since heavy crude oil-water flow is not transparent for
visual observation and online sampled pressure drop signals
may not distinguish flow regimes as annular flow, stratified
flow and etc., joint use of local sampling method effectively
overcomes the limitation of flow regimes identification by
online sampled pressure drop signals. To better understand
the flow characteristics and mixing of the oil-water mixture,
effective viscosity of the oil-water mixture is calculated and
helps to investigate mixing of crude oil-water two phases.
Effective viscosity is a calculated value based on the online
sampled pressure drop and mixture velocity during pipe
flow, as shown in Eqs. 1-4.

Pm= (1)
dl D 2
Pm ,=p + (1 ) (2)
Am = C Re" (3)

Rem m m (4)
Pm
Where dp/dl is the online sampled pressure drop gradient;
vm is the mixture velocity of oil-water two phases; ,m is
fraction factor; po, p, and pm is the density of the oil, water
and oil-water mixture respective, D is inner diameter of the
pipe, f ~ is water volume fraction, Re is the Reynolds
Number, P// is the effective viscosity of the oil-water
mixture, C and n are parameters.

Flow regimes and related characteristics

The composition of the heavy crude oil is given in Table 2.
Due to the existence of asphaltene and resin components,
which are natural surfactants helps to form water-in-oil
emulsion (E \\ o, flow regimes during heavy crude oil-water
two phase flow present their own characters that w/o
emulsion are observed in all the flow regimes occurred in
current experiment.

Five types of flow regimes at different mixture velocities
and input water volume fractions were recorded and shown
in Fig.2, which are Dwater-in-oil emulsion dispersed flow,
simplified as Ew/o Dispersed, @Ew/o and water stratified
flow, intermittent flow of Ew/o and partial segregated
water pieces, simplified as Ew/o&partial segregated w
Intermittent, 4Ew/o and semi water annular flow, and
SE \\ o and water annular flow. Sketch of the observed flow
regimes during present experiment are shown in Fig.3.
Oil Dominated Water Dominated
Region Region


n n
n n
* nfl
* n n
n fl
** G
* + n
==~==E
.,,I,,


o o
oo
o o
o o


0 0.2 0.4 0.6 0.8


* Ew/o Dispersed

* Ew/o &partial segregated
Intermittent
o Ew/o&w Stratified

w&Ew/o Semi Annular

w&Ew/o Annualr


Water fraction
Figure 2: Flow regimes of heavy crude oil-water two phase


Results









flow (60 C)

0 a CP 0 00 0 00
0 0 000000 0



(a) Ew/o Dispersed (b) Ew/o&partial segregated water
Intermittent


0 o



(c) Ew/o&water Stratified



o Annular

(e) w&Ew/o Annular


(d) w&Ew/o semi Annular



Oil Phase Water Phase
Oil Phase Water Phase


Figure 3: Sketch of the observed flow regimes

Detail information are summarized as below,
(1) Ew/o dispersed flow (flow regime 1) takes a vast
percentage in the flow regime map, which reflects the
influences of emulsification caused by asphaltene and resin
components. During flow regime pressure drop gradient
would be greatly enhanced with the increment of mixture
velocity, as shown in Fig.4. However, due to the MAOP
(maximum allowable operational pressure) restriction of
pipe material, parts of the experiment were cancelled, e.g.
WF (water fraction)=0.2, when the mixture velocity exceeds
0.5m/s. At this time, the pressure at the inlet of the pipe was
around 2.0 MPa, which is adjacent to the MAOP of our flow
loop. So there is a blank area in flow regimes map.


J 40

-30

20

0
10

a


-/- WF =0.1
S-- WF =0.2
SWF =0.35
WF =0.4
WF =0.5


- WF =0.7
0.3 0.6 0.9 1.2


Mixturevelocity(m/s)
Figure 4: Pressure drop gradient vs.
heavy crude oil-water flow (60 C)


mixture velocity of


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

As shown in Fig.4, online monitored pressure drop gradient
of the tested pipe section (E.g. WF=40% and 50%) suffers
an obvious decline when flow regime ( appears. Taking
40% water fraction as an example, pressure drop gradient
increases linearly with the mixture velocity varying from
0.1 to 0.3m/s, however, the peak appears at the mixture
velocity of 0.35m/s. If mixture velocity keeps on increasing
and exceeds the peak value, pressure drop gradient will
dramatically decrease which actually indicates the variation
of flow regimes. At the same time, the effective viscosity of
the oil-water emulsion also experiences an obvious
decreasing, from almost 2000mPa-s (Vm =0.1m/s) to nearly
just 280mPa-s (vm=0.7m/s), as shown in Fig.5.
25


2.0

S15

o 10

S05

0.0


-C-0 2 -G--0 35 --07
% -05 ----06 07I


0 0 0.2 0.4 0 6 08 10 12
Mixture velocity (m/s)
Figure 5: Effective viscosity vs. mixture velocity of heavy
crude oil-water flow (60 C)

Apparently, judging from the pressure drop gradient and
effective viscosity, it may be reasonable to draw a
conclusion that the continuous phase of the oil-water
mixture has changed with the increment of mixture velocity.
However, through local sampling analysis, it's found that oil
phase is still the main continuous phase, just accompanying
with numbers of segregated and accumulated discontinuous
water pieces. This phenomenon is due to the coalescence of
unstable w/o droplets during pipe flow with the
enhancement of mixture velocity.

To better understand the structure and mixing of the
oil-water mixture, the effective viscosity and its variations
character with time are further analyzed, as shown in Fig.6.


1.6

I 1.4

" 1.2


(2) In the oil dominated region, with the increment of
mixture velocity, shear strength and turbulence will be
enhanced and the frequency that dispersed water droplets
collided with each other will also be increased
(Coulaloglou&Tavlarides, 1977; Davies, 1992). Thus some
of the unstable w/o emulsion droplets formed in the stirred
tank previously will have more opportunities to be
coalesced during the pipe flow. Finally partial segregated
water phase could be formed and observed, which directly
leads to the flow regime transition from Ew/o Dispersed
(flow regime 1) to Ew/o&partial segregated w Intermittent
(flow regime 3). As shown in Fig.2, this scope is
approximately range from 35% to 55% water holdup in
present experiment.


l 3mh/



-f0l~mls -02m/ns --039m/


0.0 10.0 20.0 30.0 40.0 50.0
Time (s)
(a) mixture velocity 0.1~>0.3m/s


"
k,_









1.0
--0 4m/s --0.5m/s
S -0.7m/s

0.6

0 4

0 2

00 -
0.0 10 0 20 0 300 400 50 0 60.0 700
Time (s)
(b) mixture velocity 0.4~0.7m/s
Figure 6: Pressure drop gradient & effective viscosity vs.
time of heavy crude oil-water flow (WF=40%, 60 C)

1) In Fig.6 (a), when mixture velocity ranges from 0.1 to
0.3m/s, the effective viscosity of the oil-water mixture is
time independent and is 2 or 3 times larger compared to the
viscosity of the continuous oil phase, which represents that
the Ew/o system has already been established and the
oil-water mixture forms flow regime 1. As well, the Ew/o
shows its non-Newtonian characteristic that its effective
viscosity decreases with the increment of mixture velocity,
which reflects the shearing-thin behaviour of the w/o
emulsion.

2) In Fig.6 (b), it's clear that the effective viscosity of the
oil-water mixture suffer obvious fluctuation and periodical
character as the mixture velocity exceeds 0.4m/s. Taking
mixture velocity=0.5m/s as an example, the maximum
effective viscosity at the wave crest is nearly 930mPa-s,
which is nearly nine times compared to the minimum
effective viscosity (100 mPa-s) at the wave trough, so
Intermittent (flow regime ) is introduced to describe its
flow regime and character.

However, the minimum effective viscosity of oil-water
mixture is still around 100 mPa-s which is much higher
compared to viscosity of single water phase, which indicates
that the segregated water pieces only take a limited
percentage during oil-water flow. It has been verified
through local sampling analysis that it's only some
segregated and accumulated discontinuous water pieces.
Flow regime transition from E\\ o Dispersed flow" to
"Ew/o&partial segregated w intermittent flow" is first time
observed in present experiment, which will be further
discussed in Sec.4.

(3) Since the existence of asphaltene and resin components
in the heavy crude oil phase, oil-in-water emulsion (o/w) or
dispersion is hard to existed. Even at high water volume
fraction, heavy crude oil phase will also emulsify with water
phase and form dual continuous flow of Ew/o and water
phase. So with the increment of mixture velocity, flow
regimes experience the transition from Ew/o&w Stratified,
w&Ew/o Semi Annular and Annular flow with water rings
contacting the pipe inner surface. Flow regimes of Ew/o and
water Annular has already been observed by Arirachakam et
al. (1989) and Bannwart (2-1114, 2005). It's due to the high
viscosity of emulsified oil phase, thus the emulsified oil
phase is hard to be dispersed and oil-in-water dispersion is
not observed in the range of mixture velocities we have
studied in the experiment.


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

Phase inversion

Comparing with Arirachakam et al. (1989)'s research of
SN-250 and 150-SB high viscosity mineral oil-water two
phase flow, phase inversion during heavy crude oil-water
two phase flow is obviously delayed. Here, we will compare
the phase inversion phenomenon with author's previous
results on high viscosity mineral oil-water two phase flow
(Wang&Gong, 2009), which is carried out in the same
experiment facility as shown in Fig.1. The viscosities of
high viscosity mineral oil and heavy crude oil are
approximately the same, which are 620mPa-s and 628.1
mPa-s at their experimental temperature respective.

As shown in Fig.7 and 8, the relationship between pressure
drop gradient and water fraction is plotted out at different
mixture velocity. Phase inversion is nearly putted off for
25% (water volume fraction) during heavy crude oil-water
flow, compared to high viscosity mineral oil-water flow. All
in all, natural surfactants as asphaltene, resin and etc. in the
heavy crude oil phase owed to the influence on phase
inversion.

20 Inversion -*-- 0. rns
S0 -*- D.2m/s
16 l --0.3n/s
S0.4m/s
d 0. 5-Dm/s


4 --. Oms
-\---D.8m/s
U 4


0.0 0.2 0.4 0.6 0.8 1.0
Water fraction
Figure 7: Pressure drop gradient vs. water fraction of high
viscosity mineral oil-water (30 C)


40 Inversion
S, - -- O Irn/s
32 \
D0.2m/s
24 -- 0.3mn/s
C8
16



0
0 0.2 0.4 0.i 0.8
Water fraction
Figure 8: Pressure drop gradient vs. Water fraction of heavy
crude oil-water (60 C)

As have been discussed in Wang&Gong (2009)'s research,
phase inversion during high viscosity oil-water flow are best
predicted by the model of Arirachakaran et al.(1989).
However, for heavy crude oil-water two phase system, all
the above models fail to get acceptable predictions, because
none of them has taken the influence of surfactants into
consideration.

Discussion

In Sec.3, flow regimes, transition characters and related









flow characteristics during heavy crude oil-water two phase
flow have been analyzed, while two phenomenon has raise
the researchers' attention and will be further discussed. They
are:
(1) With the increment of mixture velocity, shear strength
and shear force will be enhanced as well, which would
affect the modality of dispersed emulsion droplets. Thus
flow regime transition from Ew/o Dispersed (flow regime
1) to Ew/o&partial segregated w Intermittent (flow regime
3) can be observed. As shown in Fig.4, while water
fraction range from 0.3 to 0.5, the increment of mixture
velocity will lead to the release of segregated water pieces
and flow regime transition.
The above phenomenon has rarely been reported by other
researchers. After careful consideration, a conclusion is
drawn that it's due to the discrepancy of experimental
procedure. In present experiment, with the purpose of
keeping consistent with what really happens in the oil-water
multiphase transporting pipeline in the oilfield, oil and water
phases are mixed ahead and w/o dispersion or emulsion
system are already established in the stir tank before
pumping into the flow loop. The mixing speed is elaborated
selected at which the physical properties of the formed
emulsion are approximately as the oil-water mixture
produced from the oilfield drilling well.
Since the oil-water dispersion or emulsion has already been
formed before pumping into the flow loop, its dispersed
modality especially drop size distribution is established at
the shearing strength in the stir tank. In general, the
dispersed modality is determine by the mixing strength in
the stirring tank, which can be described in terms of
impeller Weber number, We1,

d -f (We,) (5)


Where


pN2D3
ecN D
C


Here, Pc is the continuous phase density, N is the agitation
speed, and Di is the impeller diameter.
At the same time, due to the influence of natural surfactants,
surface active agents like asphaltene and resin will
uniformly distributed at the interface of water-in-oil droplets,
which will lower the oil-water interfacial tension and
enhance the interfacial elasticity. In addition, the
hydrophobic part of asphaltene and resin molecular within
the oil phase will also generate enough steric interactions
that would prevent drops from approaching very closely and
would delay coalescence (Tadros, 1996). So water-in-oil
emulsion is formed and kept in a quasi-stable status with
higher interfacial surface energy, where the input turbulence
energy during stirring process is preserved in the oil-water
system as the interfacial surface energy.
When the formed w/o dispersion / emulsion system is
transferring into the flow loop, with the increment of
mixture velocity, shear strength will be enhanced and the
frequency that dispersed droplets collided with each other
will also be promoted. Thus some of the unstable w/o


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

emulsion droplets, formed in the stirred tank previously, will
trend to coalesce and minimize the system's interfacial
surface energy. So partial segregated water phase could be
formed and flow regime transition is observed finally.
Consequently, this is different from the prevalent
experimental procedures that oil and water phases are
pumped into the flow loop separately (Trallero, 1996;
Andreini et al., 1997; Niidler &Mewes, 1997;
Angeli&Hewitt, 2000; Shi, a, b, 2001; Jin et al., 2003;
Lovick&Angeli, 2004; loannou et al., 2005; Janaa et al.,
2006). And the oil-water dispersion system is established
due to the turbulence in the flow loop during two phase flow,
so the dispersed modality is determine by the turbulence
kinetic energy, which can be described in terms of Weber
and Reynolds number, We,, Re,,

d f (We, Rec) (7)


Where


We Re,
c "


Here, v, is the velocity of the continuous phase, D is the
diameter of the pipe, and Pc is viscosity of the continuous
phase.
(2) Phase inversion process during heavy crude oil-water
flow is different from its theoretical definition which is
defined as the transition from o/w to w/o. Instead, it's
obviously influenced by the emulsification of oil and water
phase.
The reasonable explanation for the above phenomenon is
owed to the influence of surfactant ingredients as well. If
without surface active agents, phase inversion may occurs
almost the same as the one in high viscosity oil-water
system, since their physical properties are approximately the
same. However, the occurrence of inversion was delayed
with the presence of surface active agents. Even worse is
that, water-in-oil emulsion (E \\ o will also exist after phase
inversion. It's the reason that w&Ew/o Semi Annular and
Annular flow (flow regime 4 and 5) are formed after
phase inversion.
Since asphaltene and resin both have a largely hydrophobic
hydrocarbon structure containing some hydrophilic
functional groups and consequently is surface-active. Hence,
both asphaltene and resin have the potential to accumulate
on the water/oil interface and enhance the stability of
emulsion. Concerning about the role of asphaltene and resin
on emulsion properties and flow characteristics, researchers
(Yarranton, 2000, 2001; Sjoblom, 2002; Sztukowski et al.,
2003, 2005; Hannisdal, 2006) have leaded their
investigation, focusing on their influence on the interfacial
property and emulsion stability. However, most of the
investigations are still restricted in using hydrocarbon
(toluene and heptane) as their experiment materials, for the
complex composition of crude oil phase itself and
uncertainty to distinguish the combined effect of all these
ingredients (asphaltene, resin and all its compositions)
together.
Based on upper analysis, we may draw a conclusion that









present investigations on heavy crude oil-water flow provide
an insight into the flow characteristics of w/o emulsion. As
we known, crude oil from oilfield will inevitably contain
several kinds of natural surfactants; research in this area is
worth further investigating especially for the engineering
oilfield and will benefit the operation and maintains of
multiphase transportation pipeline.


Conclusions

In this paper, experimental investigation on heavy crude
oil-water two phases in horizontal pipe is conducted. Five
flow regimes are observed respectively. Results indicates
that,
(1) As natural surfactants as asphaltene and resin are existed
in heavy crude oil phase, oil and water phases are easy to
form water-in-oil emulsion, so heavy crude oil and water
tends to form Ew/o dispersed flow.
(2) With the increment of mixture velocity, shear strength
will be enhanced, which would affect the modality of
dispersed emulsion droplets. Thus flow regime transition
from Ew/o Dispersed to Ew/o&partial segregated w
Intermittent are observed.
(3) Natural Surfactants as asphaltene, resin and etc. play an
important effect on phase inversion process, which will
obviously delay the occurrence of inversion process. Phase
inversion during heavy crude oil-water flow is different
from its theoretical definition. Instead, it's obviously
influenced by the emulsification of oil and water phase.

Acknowledgements

The authors wish to thank the National Major Science
Project and National Natural Science Foundation of China
for providing support for this project.


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7th International Conference on Multiphase Flow
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7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010


Table 1 Property of heavy crude oil

Temperature / C 40 45 50 55 60 65 70

Density/kg-m3 963.43 960.74 958.05 955.36 952.66 949.97 947.28

Viscosity/ mPas 3245 2109 1351 898.5 628.1 449.9 327.3


Table 2 Compositions of the heavy crude oil
Saturated Aromatic Asphaltene
Composition Non-hydrocarbon
hydrocarbon hydrocarbon & Resin
Mass percentage (%) 25.46 35.95 15.70 22.89


Table 3 Prediction of inversion points from present experiments
Heavy crude oil-water
60 C 70C
Researchers Inversion Model
Inversion point=0.5 Inversion point=0.52
PV PD PV PD
Yeh et al.(1964) 1/(1+(P)5) 0.026 -94.78 0.033 -92.32
Arirachakaran et al.(1989) 0.5-0.11081g(p) 0.153 -69.69 0.176 -60.80
Decarre&Fabre(1997) 1 (1 p)6) 0.236 -52.80 0.253 -45.50
Brauner&Ullmann(2002) 1 (1()" 4(p)6") 0.053 -89.30 0.065 -84.40




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