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


The Flow Pattern Study of Oil-gas-water Three-phase Flow in Horizontal Circular
Gathering and Transferring Pipeline in Oil Field


Xiaoyan Liu, Dianwei Liu, Qianjun Mao and Jiajia Liu

Daqing Petroleum Institute, Civil and Architecture Engineering, Department of Built Environment, Thermal Power
Engineering
199, FaZhan Street, SaErTu, Daqing, 163318, China
renenegoncheng@126.comco


Keywords: flow pattern, horizontal pipe, oil-gas-water, circular gathering and transferring process



Abstract

At present, with deeply exploitation of the oil field in the eastern land of CHINA, the water-cut of most oil wells exceeds by
85%, and some have even reached 95%. The flow pattern study on oil-gas-water three-phase flow is the basis for determining
mixed transportation limits with super high water-cut, researching of hydro-thermal calculation method and scientific
operation management of gathering and transferring system. In order to study oil-gas-water three-phase flow pattern of
circular gathering and transferring pipeline in low-permeability oil fields, we developed a certain set of test device in Daqing
oil field with a series of experiments. 1360 groups of oil-gas-water three-phase flow pattern photographs and the
corresponding flow parameters have been acquired. Five flow patterns are summarized in horizontal circular gathering and
transferring pipeline for the first time, including stratified flow: three-layer disturbed flow: wave surging flow: gas bombs
mixing flow and complete mixing flow. We gave the range of corresponding parameters to each flow pattern, and explained
the typical character of each flow pattern.


Introduction

The oil-gas-water mixture flow from the well head to the
transfer station belongs to multiphase flow [1]. The flow
pattern reflects the character of three-phase flow system
from an important aspect [2]. The crude oil of most oil
fields belongs to paraffin-base crude oil in CHINA. In order
to ensure the safety of gathering and transferring crude oil,
heated oil transportation process has been widely used in
early stage. In China, transporting 1 ton crude oil averagely
consume 15~-35m3 natural gas. With deeply exploitation of
the oil field in the eastern land of China, the water-cut of
most oil wells exceeds 85%, and heating gathering crude oil
needs enormous thermal energy.
In the early 1990's, some well-know scholars from all over
the world have already divided the flow pattern of
multiphase flow [3-6], but so far there is no uniform
definition in oil-gas-water three-phase flow pattern. The
division of flow pattern and the research of the multiphase
flow mechanism of mutual transformation are mostly based
on lab experiments [7,8]. It is different from the
oil-gas-water three-phase and needs proof in gathering and
transferring pipeline. The study of flow pattern on
oil-gas-water three-phase flow is the basis for determining
mixed transportation limits with super high water-cut, and it
has very important practical significance for the researching
of hydro-thermal calculation method.
The wells of middle-permeability and high-permeability oil
fields and pipelines are connected by branch-shaped pipe
network. There is already some research on oil-gas-water
three-phase flow pattern [9]. At present, low-permeability


oil field production have increasing year by year, and its
position also becomes more and more important. In 2008,
our national production of low-permeability crude oil
reached 0.71 million tons, about 37.6% of the country's
total annual output. The well in low-permeability oil fields
and pipelines are connected by circular pipeline network.
There have been no relevant reports on oil-gas-water
three-phase flow pattern of circular gathering and
transferring pipeline in low-permeability oil fields yet. In
this paper, we develop a certain set of test device in
low-permeability oil fields to test oil-gas-water pattern and
the corresponding flow parameters in circular gathering and
transferring pipe network, finally analyze the experiment
results.


Nomenclature


the water amount injected per hour (m /h)
liquid phase superficial velocity (m/s)
oil phase superficial velocity (m/s)
volume oil-bearing ratio (%)
volume liquid water cut (%)
viscosity (mPas)
volume gas-bearing ratio (%)
solidifying point of crude oil ("C)
density of the crude oil at 20"C (kg m )
density of the crude oil at 50"C (kg m )

















































01 1 I I I I
1. 74 1. 59 1. 38 1. 28 1. 16 1. 01
Msm/h]

Figure 3: the change trends of superficial velocity

With the water amount injected per hour, the changing
regular pattern of the ratio of oil-gas-water is shown as
Figure 4.


The test is done mn an oil production plant of Daqing. The
crude oil is called "three highs", which means high viscosity,
high solidifying point and high wax content. There are the
main parameters in Table 1.
Table 1: the parameters of crude oil

9 pso P20 Wax gum asphaltene

/"C /kg- nE /kg- nE" /% /% /%

42 845.0 864.9 27.20 15.14 1.27


Characteristic curves of viscosity and temperature

We tested the viscosity of crude oil at the four different
shear rates(15.4s :; 76.8s :; 230s :; 384s '), and drew the
characteristic curves of viscosity and temperature of the
gathering and transferring system, as shown in Figure 2.





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


Experimental Facility

In order to study the flow pattern, testing pipe length is
chosen at end of the scavenge pipe. A bypass is fixed at the
test section, a transparent quartz glass pipe of diameter
76mm and the pipeline (steel pipe of diameter 76mm) is
connected by a crude oil repair clip. The technological
process chart of test is shown as Figure 1.


45 50 5
temperature/


5 60 65


Figure 2: characteristic curves of viscosity and temperature

The changing regular pattern of every parameter with
the water amount

With the water amount injected per hour, the changing
regular pattern of every phase superficial velocity is shown
as Figure.
0. 2

Liquid phase speed(m/s)

g oil phase speed(m/s)

0. 1


Figure 1: The technological process chart

The hot water amount of the main pipe into the pipe
network is controlled by a valve in metering plant. The
mixture of oil-gas-water that comes from every well is
poured into the pipe network and mixes with the hot water,
then flows through the flow pattern test pipe, finally gathers
to scavenge pipe and gets into the metering plant. During
the experiment, the water temperature is controlled about
62"C, the water amount in the metering plant is reduced
from1.74 m3/h to 1.01m3/h. Flow pattern photographs and
the corresponding parameters of every moment are
collected.


Numerical Scheme
The basic physical parameters of crude oil


80
70
60
50
40
30

10

o


volume gas-bearing ratio(%)


-Cvolume oil-bearing ratio(%)


volume water-bearing ratio of


1.74 1.59 1.38 1.28 1. 16 1.01

M [m /h]

Figure 4: the change trends of the ratio of oil-gas-water

Results and Discussion

The well-known scholars at home and abroad all adopted
the relations between liquid-phase and pipe wall, oil-phase
and liquid phase, gas-phase and liquid-phase to define the
oil-gas-water three-phase flow pattern. Because of the






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


particularity of oil-gas-water three-phase flow during the
process of mixed transport: Firstly, because of the stroke
moving up and down of the beam pumping unit, the
pressure in the pipe network fluctuates with the mixture
from oil well injected into the pipe network, which means
the three-phase is not flowing in the condition of the
constant pressure; Secondly, the oil-water rate of the
mixture is not a constant at different moments, and it is
enough to impact the change of flow pattern and the
opposite phase point; Finally, the superficial velocity of gas
phase is changing. The oil-gas-water three-phase flow
pattern is not completely the same as the results in the lab.
So we make classify according to the special flow patten
and typical characteristics of oil-gas-water mixture in the
pipeline.

Stratified flow

The range of parameters: liquid phase speed is
0.127~0.114m/s; volume gas-bearing ratio is
76.39 ~78.40%; volume oil-bearing ratio is 3.49 -3.58%
and volume liquid water cut is 85.22 -83.41%. The
stratified flow is shown as Figure 5.


Figure 6: Three-phase disturbed flow


Mechanism: the turbulence active force between oil and
water is nearly the same as the interface tension. At the
beginning oil droplets disperse into the water, but the
turbulent force between oil and water is not enough to make
them completely disperse into the water. The oil droplets
only disperse on the interface between oil and water. The
water cut of oil layer and water layer at the cross-section
sometimes changes suddenly. It shows that the oil layer is
mixed with water layer. Gas phase, oil phase and water
phase are divided into three layers, the interface between oil
and water is not clear.
Typical Characteristics: because the pressure fluctuates in
the pipeline when oil-gas-water mixture is injected by the
beam pumping unit and the mixed transporting three phase
is not steady (the superficial velocity of gas-phase is
changing every moment), groups of high-speed "oil puddle"
flow through, and causes a strong disturbance, which
disturbs the steady flow state of three layers under the
maintenance of the original gravity and makes the oil
droplets disperse into the water phase. The oil droplets float
onto the interface between oil and water again because of
the effect of gravity after all the "oil puddle" flow past.

Wave shock flow

The range of parameters: liquid phase speed is
0.101~0.095m/s; volume gas-bearing ratio is
80.37 ~81.34%; volume oil-bearing ratio is 3.67 ~3.72%
and volume liquid-bearing ratio is 81.29% ~ 80.08%. The
wave shock flow is shown as Figure 7.


Figure 5: Stratified flow


Mechanism: gravity plays the dominant role. Gas phase is
bubbly and the air bubble gathers at the top of the pipeline;
the thin oil layer keep stratified flowing on the water layer;
the water phase flows under it. The mixture flows at a low
speed. The interface between oil and water is clear. There is
almost no gas in the lower part of the pipe's cross-section. It
shows that the power of turbulent is far less than the
buoyancy.
Typical Characteristics: the three-phase mixture flow is not
like the oil-gas-water three-phase flow in the lab at the same
pressure and quantification in the gathering and transferring
pipeline at oil field. with the stroke moving up and down of
the beam pumping unit, the pressure in the pipeline is
fluctuating. When the pressure wave researches the test
point, the typical characteristic is that a small group of "oil
puddle" will quickly flow through the interface between oil
and water.

Three-layer disturbance flow

The range of parameters: liquid phase speed is
0.114~0.101m/s; volume gas-bearing ratio is
78.40 ~80.37%; volume oil-bearing ratio is 3.58 -3.67%
and volume liquid-bearing ratio is 83.41 /~81.29%.
Three-phase disturbed flow is shown as Figure 6.


Figure 7: Wave shock flow


Mechanism: the turbulent active force between oil and water
is greater than the interface tension. Some droplets diffuse
down by the force of fluctuation, but they can not
completely overcome the gravity. The gas-oil two-phase is
wave layer, and the interface between oil and water is not
clear. The water cut increases from top to bottom of the pipe
cross-section, it shows the oil and water are mixed with
each other intensity.
Typical Characteristics: the interface between oil and water






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


is wave flow in the pipeline. The wave pattern is similar to
the sine wave, the cyclical of the interface wave is clear. The
pressure fluctuates in the pipeline. With interface wave flow
through, slight stagnation and backward flow appear. When
the peak of back flow wave meets the next interface wave
peak, it is able to form superposition of interface waves
which is up to the top of the pipe and flow through the
pipeline.

Gas bombs mixing flow

The range of parameters: liquid phase speed is
0.095~0.087m/s; volume gas-bearing ratio is
81.34"..--s2 54%; volume oil-bearing ratio is 3.72 -3.77%
and volume liquid-bearing ratio is 80.08 ~78.40%. The gas
bombs mixing flow is shown as Figure 8.


Figure 9: Gas bombs mixing flow


Mechanism: because the turbulence force and the action of
gas-phase further increases, oil-water two-phase is strong
enough to overcome the force of buoyancy and gravity. It
makes the oil-water two-phase completely break into
homogeneity, the gas-bearing ratio and liquid-bearing ratio
of the whole cross-section of the pipe is nearly the same. It
shows that the three-phase is mixed completely. The
gas-phase and liquid-phase are tomn into flaky, small bubbles
and liquid droplets flow with the mix-phase.
Typical Characteristics: the pressure fluctuates in the
pipeline as inject mixture from the beam pumping unit,
together with the disturbance of gas-phase, the dispersed
state of gas-phase and liquid-phase in the pipeline also
changes. The continuity of gas-film and water-film is
broken from time to time, and the flow characteristic of
mixed-phase is closer to the homogeneous state.

Conclusions

1) We developed a certain set of flow pattern test device in
Daqing low-permeability oil field. A series of experiments
are done about oil-gas-water three-phase flow pattern in
circular gathering and transferring pipeline. 1360 group of
oil-gas-water three-phase flow pattern photographs and the
corresponding test parameters have been acquired.

2) Viscosity and density of the crude oil has been tested. We
analyzed the changing regular pattern of oil phase speed,
water phase speed, volume gas-bearing ratio, volume
oil-bearing ratio and volume water-bearing ratio with the
content of water decreasing.

3) The photographs of the flow patterns and the test data
have been analyzed. Five flow patterns are summarized in
horizontal circular gathering and transferring pipeline,
including stratified flow: three-layer disturbed flow: wave
impact on stream flow: gas bombs mixing flow and
complete mixing flow. The ranges of corresponding
parameters of each flow pattern have been given.

4) The typical character of each flowing state is described,
and the mechanism of each flow pattern is explained.

Acknowledgements

The authors gratefully acknowledge the financial support
from the Scientific and technological project in
Heilongjiang Province (Grant No. GBO8A304). We would
also like to thank the support of Daqing Oilfield for
supplying experimental site. Finally, we appreciate the
guidance of Lecturer Xu Ying.


Figure 8: Gas bombs mixing flow

Mechanism: under the both actions of the increasing force
of turbulence and the disturbance of gas phase, oil-water
two-phase overcomes most of actions of buoyancy and
gravity, and is broken into mixed phase which can blend
with each other. However, it is not enough to make the
oil-water two-phase completely mix. The gas-bearing ratio
in the section of pipeline changes fiercely. The thin layer of
water-phase flows at the bottom of the pipeline. When the
"gas bombs" flow through the pipe, the speed of mixture
rises up quickly, and the oil-water mixed-phase flows in the
lower part of the pipeline.
Typical Characteristics: the pressure in the pipeline
fluctuates as the injecting mixture from the beam pumping
unit, after a "gas bomb" flows through, it will be
accompanied by stagnation and flow back. The flowing
frequency and length of the "gas bomb" will change. When
the beam pumping unit is in upstroke, the pressure increases
in the pipeline, the disturbance of gas-phase becomes
intensive, then the length of the "gas bomb" is short and the
frequency is high. When the beam pumping unit is in down
stroke, the pressure decrease in the pipeline, then the length
of the "gas bomb" is long and the frequency is low.

Complete mixing flow

The range of parameters: liquid phase speed is
0.087~0.078m/s; volume gas-bearing ratio is
82.54"..--s4.08%; volume oil-bearing ratio is 3.77 -3.84%
and volume liquid-bearing ratio is 78.40 ~75.86%. The gas
bombs mixing flow is shown as Figure 9.





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


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