The Role Analysis of Superheated Steam Injection to Improve Performance in Thin Heavy Oil Reservoir Zhanxi Pang Faculty of Petroleum Engineering, China University of Petroleum, Beijing, China Email: [email protected] Chengxiang Qi Section of Reservoir Development, CNOOC Iraq Limited, Beijing, China Email: [email protected] Abstract—Superheated steam has some special properties, such as high temperature but low pressure, high quality (100%), higher latent heat and larger specific volume. In this article, numerical simulation technology was employed to analyze performance of cyclic superheated steam stimulation in thin heavy oil reservoirs with different net pay, such as 1-3 m, 3-5 m and 5-10 m. By contrasting of incremental oil production, saving volume of steam consumption, distribution features of reservoir temperature and oil saturation after injecting conventional wet steam, hot saturated steam and superheated steam, the technological advantages of cyclic superheated steam stimulation was analyzed to develop heavy oil reservoirs. The results showed that incremental oil ability of superheated steam was much higher than conventional wet steam and hot saturated steam, but the degree of incremental oil gradually became slower when superheated degree was over 20 o C. When the same volume of heavy oil was produced by the three kinds of steams, superheated steam could save steam consumption. Index Terms—superheated steam; heavy oil reservoir; cyclic steam stimulation; EOR; numerical simulation I. INTRODUCTION In the last few decades, steam injection has been recognized as an important method to develop heavy oil reservoirs.[1] Current interest in steam injection method is toward the use of superheated steam, which presents higher temperature at the same pressure. The technology of superheated steam injection has been applied in some heavy oil reservoirs, such as Henan Oilfield in China and Pre-salt reservoir of Kenjiyak Oilfield.[2] [3] Superheated steam is a kind of special steam whose temperature is above the corresponding saturated temperature at a given pressure. Compared with the conventional wet steam, superheated steam has some characteristics, such as elevated temperature, high quality, low pressure, large specific volume and etc.[4] Therefore, there are some obvious differences between superheated steam and Manuscript received November 5, 2013; revised April 15, 2014. saturated steam to development heavy oil reservoirs. Many experimental results showed that superheated steam could prompt some physical and chemical changes of minerals and fluids in heavy oil reservoirs to result in a large reduction of oil viscosity or flow resistance.[2]-[4] In this article, based on the analysis of EOR mechanisms, the technology of numerical simulation was employed to study technology advantages and performance characteristics of cyclic superheated steam stimulation in heavy oil reservoirs. II. RECOVERY MECHANISMS Superheated steam is water phase at a special state. The recovery mechanisms can be summarized as following. Viscosity reduction: The viscosity of heavy oil is very sensitive to temperature. High temperature largely reduces the viscosity of heavy oil to result in decreasing flow resistance in reservoirs.[5] Therefore, viscosity reduction is the most important mechanisms during superheated steam injection. Distillation effect: Superheated steam is at a state of high temperature but low pressure. Therefore, superheated steam can obviously increase distillation efficiency of crude oil, especially heavy oil.[6] Thermal expansion: The thermal expansion degree of heavy oil and rock minerals is larger under higher temperature and heat during superheated steam injection.[2]-[5] Hydrothermal cracking: Heavy oil occur a series of chemical reactions, such as desulfurization, denitrogenation, hydrogenation. The hydrothermal cracking reactions largely decrease heavy oil viscosity, reduce the content of sulfur, oxygen and nitrogen in heavy oil to improve its flow ability in porous media.[7] Plugging removal: A flushing effect from high speed steam can effectively remove drilling fluid Journal of Industrial and Intelligent Information Vol. 2, No. 3, September 2014 189 2014 Engineering and Technology Publishing doi: 10.12720/jiii.2.3.189-193
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The Role Analysis of Superheated Steam
Injection to Improve Performance in Thin Heavy
Oil Reservoir
Zhanxi Pang Faculty of Petroleum Engineering, China University of Petroleum, Beijing, China
Email: [email protected]
Chengxiang Qi Section of Reservoir Development, CNOOC Iraq Limited, Beijing, China
Email: [email protected]
Abstract—Superheated steam has some special properties,
such as high temperature but low pressure, high quality
(100%), higher latent heat and larger specific volume. In
this article, numerical simulation technology was employed
to analyze performance of cyclic superheated steam
stimulation in thin heavy oil reservoirs with different net
pay, such as 1-3 m, 3-5 m and 5-10 m. By contrasting of
incremental oil production, saving volume of steam
consumption, distribution features of reservoir temperature
and oil saturation after injecting conventional wet steam,
hot saturated steam and superheated steam, the
technological advantages of cyclic superheated steam
stimulation was analyzed to develop heavy oil reservoirs.
The results showed that incremental oil ability of
superheated steam was much higher than conventional wet
steam and hot saturated steam, but the degree of
incremental oil gradually became slower when superheated
degree was over 20 oC. When the same volume of heavy oil
was produced by the three kinds of steams, superheated
steam could save steam consumption.
Index Terms—superheated steam; heavy oil reservoir; cyclic
steam stimulation; EOR; numerical simulation
I. INTRODUCTION
In the last few decades, steam injection has been
recognized as an important method to develop heavy oil
reservoirs.[1] Current interest in steam injection method
is toward the use of superheated steam, which presents
higher temperature at the same pressure. The technology
of superheated steam injection has been applied in some
heavy oil reservoirs, such as Henan Oilfield in China and
Pre-salt reservoir of Kenjiyak Oilfield.[2] [3] Superheated
steam is a kind of special steam whose temperature is
above the corresponding saturated temperature at a given
pressure. Compared with the conventional wet steam,
superheated steam has some characteristics, such as
elevated temperature, high quality, low pressure, large
specific volume and etc.[4] Therefore, there are some
obvious differences between superheated steam and
Manuscript received November 5, 2013; revised April 15, 2014.
saturated steam to development heavy oil reservoirs.
Many experimental results showed that superheated
steam could prompt some physical and chemical changes
of minerals and fluids in heavy oil reservoirs to result in a
large reduction of oil viscosity or flow resistance.[2]-[4]
In this article, based on the analysis of EOR mechanisms,
the technology of numerical simulation was employed to
study technology advantages and performance
characteristics of cyclic superheated steam stimulation in
heavy oil reservoirs.
II. RECOVERY MECHANISMS
Superheated steam is water phase at a special state.
The recovery mechanisms can be summarized as
following.
Viscosity reduction: The viscosity of heavy oil is
very sensitive to temperature. High temperature
largely reduces the viscosity of heavy oil to result
in decreasing flow resistance in reservoirs.[5]
Therefore, viscosity reduction is the most
important mechanisms during superheated steam
injection.
Distillation effect: Superheated steam is at a state
of high temperature but low pressure. Therefore,
superheated steam can obviously increase
distillation efficiency of crude oil, especially
heavy oil.[6]
Thermal expansion: The thermal expansion degree
of heavy oil and rock minerals is larger under
higher temperature and heat during superheated
steam injection.[2]-[5]
Hydrothermal cracking: Heavy oil occur a series
of chemical reactions, such as desulfurization,
denitrogenation, hydrogenation. The hydrothermal
cracking reactions largely decrease heavy oil
viscosity, reduce the content of sulfur, oxygen and
nitrogen in heavy oil to improve its flow ability in
porous media.[7]
Plugging removal: A flushing effect from high
speed steam can effectively remove drilling fluid
Journal of Industrial and Intelligent Information Vol. 2, No. 3, September 2014
1892014 Engineering and Technology Publishingdoi: 10.12720/jiii.2.3.189-193
pollution near well bore. The plugging material
can be produced along with hot oil, steam and
condensate water during production to decrease
flow resistance near well bore.[7]-[9]
Emulsification flooding: Light distillate of heavy oil
generates oil-in-water emulsion or water-in-oil emulsion
in the front of steam condensate in reservoirs. [10] [11]
The viscosity of oil-in-water emulsion is larger than
water and the viscosity of water-in-oil is larger than oil.
Therefore, the flow resistance gradually increases in
higher permeable formation to decrease steam fingering
and improve steam sweep efficiency in reservoirs.
III. PRODUCTION PERFORMANCE ANALYSIS
A. Basic Parameters
According to the geological characteristics, such as,
shallow depth, thin thickness and high viscosity, in
Henan Oilfield, a series of reservoir parameters were
chosen for numerical simulation in this article. The
reservoir depth was 220 m. The net pay was respectively
chosen 1.8 m, 4.2 m and 6.0 m. The absolute permeability
was 1250×10-3
μm2. The porosity was 31%. The initial oil
saturation was 65%. The initial reservoir temperature was
26 oC. In order to simulate distillation effect of crude oil,
oil component was split light oil, medium oil and heavy
oil, as listed in Table I. During numerical simulation, wet
steam was injected into reservoirs in the first cycle and
then superheated steam was injected into reservoirs from
the second cycle. The steam quality was chosen 54% for
wet steam at 260oC. The higher quality 80% for higher
temperature of wet steam at 300oC. The superheated
degree was respectively chosen 0.0, 20.0 and 50.0oC for
superheated steam at 300 oC. [12]
TABLE I. TYPE SIZES FOR CAMERA-READY PAPERS
Components Properties
Water Light oil Medium oil Heavy oil
Molal weight
(kg/mol) 0.018 0.030 0.150 0.300
Mass density (kg/m3)
1000.0 821.0 903.0 976.0
Critical pressure
(MPa) 22.048 3.551 1.965 0.00
Critical temperature
(oC) 374.15 90.0 250.0 0.0
Volatilizable (yes or no)
yes yes yes no
B. The Analysis of Oil Production
According to the range of net pay in Henan Oilfield,
thin heavy oil reservoir was classified three cases, such as
1-3m, 3-5m and 5-10 m. The incremental oil ability was
analyzed for wet steam and superheated steam to
compare the cumulative oil production of 260oC wet
steam, 300oC wet steam and different superheated degree
of superheated steam. For thin heavy oil reservoirs with
different thickness, the cumulative oil production of
superheated steam is obviously higher than wet steam, as
shown in Fig. 1. The cumulative oil production gradually
increases as superheated degree or steam quality
increases. For superheated steam injection, the
cumulative oil production basically linearly increases as
superheated degree increases. The results show that the
incremental oil ability of superheated steam gradually
increases as superheated degree increases, as shown in
Fig. 1 (d). The degree of incremental oil is larger for
thinner net pay, which presents superheated steam has a
certain advantage in thinner heavy oil reservoirs. The
reason lies in higher temperature and quality of
superheated steam. The temperature of oil reservoirs is
higher during cyclic superheated steam stimulation than
cyclic wet steam stimulation. The difference of oil
production is larger more and more as the stimulation
cycles increases. Meanwhile, the volume of steam
chamber is larger for superheated steam than wet steam
under reservoir conditions, which shows that the swept
volume of superheated steam is larger during injection
stage. [2]
1100
1150
1200
1250
1300
1350
1400
1450
1500
Cu
mu
lati
ve o
il p
rod
uti
on
(m3
)
0
3
6
9
12
15
To
tal
en
thalp
y i
nje
cti
on
(1
06 K
J)
Cumulative oil production
Total enthalpy injection
300℃+50℃
300℃+20℃
300℃+0℃
300℃+90%
300℃+80%
260℃+54%
300℃+50℃
300℃+20℃
300℃+0℃
300℃+90%
300℃+80%
260℃+54%
Temperature+Quality
Temperature+Superheated degree
(a) 1-3m net pay
2200
2300
2400
2500
2600
2700
2800
Cu
mu
lati
ve o
il p
rod
uti
on
(m3
)
0
4
8
12
16
20
To
tal
en
thalp
y i
nje
cti
on
(1
06 K
J)Cumulative oil production
Total enthalpy injection
300℃+50℃
300℃+20℃
300℃+0℃
300℃+90%
300℃+80%
260℃+54%
300℃+50℃
300℃+20℃
300℃+0℃
300℃+90%
300℃+80%
260℃+54%
Temperature+Quality
Temperature+Superheated degree
(b) 3-5m net pay
3500
3700
3900
4100
4300
4500
Cu
mu
lati
ve o
il p
rod
uti
on
(m3
)
0
5
10
15
20
25
To
tal
en
thalp
y i
nje
cti
on
(1
06 K
J)
Cumulative oil production
Total enthalpy injection
300℃+50℃
300℃+20℃
300℃+0℃
300℃+90%
300℃+80%
260℃+54%
300℃+50℃
300℃+20℃
300℃+0℃
300℃+90%
300℃+80%
260℃+54%
Temperature+Quality
Temperature+Superheated degree
(c) 5-10 m net pay
Journal of Industrial and Intelligent Information Vol. 2, No. 3, September 2014
1902014 Engineering and Technology Publishing
0
3
6
9
12
15
1 2 3 4 5 6
Th
e p
erc
en
tag
e o
f in
cre
men
tal
oil
pro
du
cti
on
(%
)
1-3m
3-5m
>5m
The p
erc
enta
ge o
fin
cre
menta
l o
il p
rod
ucti
on (
%)
300℃+50℃
300℃+20℃
300℃+0℃
300℃+90%
300℃+80%
260℃+54%
300℃+50℃
300℃+20℃
300℃+0℃
300℃+90%
300℃+80%
260℃+54%
Temperature+Quality
Temperature+Superheated degree
(d) Incremental oil percentage for different net pay
Figure 1. The results of incremental oil ability for different net pay
C. The Analysis of Steam Saving
Based on the oil production of wet steam with quality
of 54% at 260oC, numerical simulation was employed to
study the amount of steam injection to achieve the same
oil production for different steam, such as wet steam with
quality of 54% at 260oC, wet steam with quality of 80%
at 300oC, superheated steam with superheated degree of
0oC, 20
oC and 50
oC at 300
oC. For 1-3 m heavy oil
reservoirs, if the amount of steam consumption was
regarded as 100% for wet steam with quality of 54% at
200oC, the amount was 89% for wet steam with quality of
80% at 300oC, and the amount are respectively 81%, 78%
and 75% for superheated steam with superheated degree
of 0oC, 20
oC and 50
oC at 300
oC (superheated steam
temperature), as shown in Fig. 2 (a). Fig. 2 (b) tells us
that the amount of steam saving are respectively 15.0%,
22.5%, 25.5% and 28.5% for different steam, such as
80 % wet steam at 300oC, dry steam (superheated degree
of 0oC) at 300
oC, superheated steam with superheated
degree of 20oC and 50
oC at 300
oC in heavy oil reservoirs
with net pay of 3-5 m. Fig. 2 (c) tells us that the amount
of steam saving are respectively 15%, 25%, 29% and
31% for different steam in heavy oil reservoirs with net
pay above 5 m. Therefore, the cumulative steam injection
of cyclic wet steam stimulation is far greater than cyclic
superheated steam stimulation at the same oil production.
The amount of steam injection gradually decreases with
steam quality or superheated degree increases, as shown
in Fig. 2 (d). The percentage of steam consumption
decreases as net pay increases, which presents that the
thermal efficiency is higher for high quality wet steam or
superheated steam in heavy oil reservoirs with the same
net pay.
50
60
70
80
90
100
Th
e p
erc
en
tag
e o
f st
eam
co
nsu
mp
tio
n (
%)
8.0
8.4
8.8
9.2
9.6
10.0
To
tal
en
thalp
y i
nje
cti
on
(1
06 K
J)
Cumulative oil production
Total enthalpy injection
300℃+50℃
300℃+20℃
300℃+0℃
300℃+90%
300℃+80%
260℃+54%
300℃+50℃
300℃+20℃
300℃+0℃
300℃+90%
300℃+80%
260℃+54%
Temperature+Quality
Temperature+Superheated degree
(a) 1-3m net pay
50
60
70
80
90
100
Th
e p
erc
en
tag
e o
f st
eam
co
nsu
mp
tio
n (
%)
11.0
11.5
12.0
12.5
13.0
13.5
14.0
To
tal
en
thalp
y i
nje
cti
on
(1
06 K
J)
Cumulative oil production
Total enthalpy injection
300℃+50℃
300℃+20℃
300℃+0℃
300℃+90%
300℃+80%
260℃+54%
300℃+50℃
300℃+20℃
300℃+0℃
300℃+90%
300℃+80%
260℃+54%
Temperature+Quality
Temperature+Superheated degree
(b) 3-5m net pay
50
60
70
80
90
100
Th
e p
erc
en
tag
e o
f st
eam
co
nsu
mp
tio
n (
%)
13.0
13.5
14.0
14.5
15.0
15.5
16.0
To
tal
en
thalp
y i
nje
cti
on
(1
06 K
J)
Cumulative oil production
Total enthalpy injection
300℃+50℃
300℃+20℃
300℃+0℃
300℃+90%
300℃+80%
260℃+54%
300℃+50℃
300℃+20℃
300℃+0℃
300℃+90%
300℃+80%
260℃+54%
Temperature+Quality
Temperature+Superheated degree
(c) 5-10 m net pay
0
5
10
15
20
25
30
35
40
1 2 3 4 5 6
Th
e p
erc
en
tag
e o
f sa
vin
g s
team
co
nsu
mp
tio
n (
%)
1-3m
3-5m
>5m
The p
erc
enta
ge
of
savin
g s
team
co
nsu
mp
tio
n (
%)
300℃+50℃
300℃+20℃
300℃+0℃
300℃+90%
300℃+80%
260℃+54%
300℃+50℃
300℃+20℃
300℃+0℃
300℃+90%
300℃+80%
260℃+54%
Temperature+Quality
Temperature+Superheated degree
(d) The percentage of steam consumption for different steam
Figure 2. The results of steam consumption for different net pay
D. The Analysis of Reservoir Properties
The distributions of reservoir temperature are shown in
Fig. 3. The results show that the heating area of
superheated steam is obviously larger than wet steam in
heavy oil reservoir with the same net pay. For cyclic
superheated steam simulation, the heating area gradually
increases as superheated degree increases. The heating
area of dry steam is slightly lower than superheated steam
with a given superheated degree. While the superheated
degree is over 20oC, the heating zone basically increases
no longer. It is the reason why the cumulative oil
production slightly increases when superheated degree is
over 20oC that there is the almost same temperature and
heating area in the same reservoir. The distribution of oil
saturation is shown in Fig. 4. For the same mass of steam
injection, the area of low oil saturation is larger after
injecting superheated steam than injecting wet steam. The
area of low oil saturation is slightly lower after injecting
dry steam than injection superheated steam, as shown in
Fig. 4. Therefore, for superheated steam, on the one hand
Journal of Industrial and Intelligent Information Vol. 2, No. 3, September 2014
1912014 Engineering and Technology Publishing
the larger specific volume increases swept volume of
steam injection, on the other hand, the stronger
distillation effect increases oil displacement efficiency in
reservoirs. The two aspects can greatly improve oil
recovery efficiency of heavy oil reservoirs.
42
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54% wet steam at 260oC
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80% wet steam at 300oC
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Dry steam at 300oC
(steam quality 100%)
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14442
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297 76
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Superheated steam at 300oC
(superheated degree 20oC)
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Figure 3. The temperature distribution for different steam in the same reservoir
0.65
0.65
0.60
0.600.55
0.650.60
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5
0.500.60 0.55
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0.55
0.60
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
010
0.000.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.951.00
80% wet steam at 300 oC
0.60
0.65
0.55 0.60
0.6
5
0.55
0.60
0.50 0.55
0.50
0.50 0.60
0.55
0.45 0.50
0.60
0.45
0.5
5
0.40
0.4
5
0.30
0.5
0
0.15 0
.45
0.1
5
0.5
0
0.15 0.4
5
0.45
0.30
0.40
0.60 0.45
0.5
5
0.55
0.45 0.50
0.500.5
0
0.60
0.600.50 0.5
5
0.65
0.55
0.55 0.60
0.60 0.65
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
010
0.000.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.951.00
0.60
0.65
0.550.60
0.550.65
0.60
0.500.55
0.65 0.50
0.60
0.55
0.45
0.50 0.45
0.6
0
0.55
0.35 0.50
0.6
0
0.4
5
0.20
0.5
5
0.5
0 0.15
0.45
0.6
0
0.4
0
0.1
5
0.5
0
0.15
0.450.60
0.450.
20
0.5
5
0.55
0.35
0.50
0.50
0.45
0.6
0
0.55
0.45
0.650.5
0
0.60
0.600.50
0.55
0.600.55
0.65
0.65
0.55
0.60
-10 0 10 20 30 40 50 60 70 80 90 100 110 120
-10 0 10 20 30 40 50 60 70 80 90 100 110 120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
010
0.000.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.951.00
Dry steam at 300 oC
(steam quality 100%)
0.60
0.65
0.550.60
0.55
0.6
5
0.60
0.50 0.55
0.65 0.50
0.60
0.55
0.45
0.50 0.45
0.60
0.55
0.30 0.50
0.6
0
0.4
5
0.15
0.5
5
0.50 0.45
0.6
0
0.4
0
0.1
5
0.5
0
0.45
0.60
0.45
0.15
0.5
5
0.55
0.30 0.50
0.500.45
0.6
0
0.55
0.45
0.650.5
0
0.60
0.60
0.500.5
5
0.60 0.550.65
0.65
0.55
0.60
-10 0 10 20 30 40 50 60 70 80 90 100 110 120
-10 0 10 20 30 40 50 60 70 80 90 100 110 120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
010
0.000.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.951.00
Superheated steam at 300 oC
(superheated degree 20 oC)
0.60
0.65
0.55 0.60
0.65
0.55
0.60
0.50 0.55
0.50
0.50 0.60
0.55
0.45 0.50
0.60
0.45
0.5
5
0.40
0.4
5
0.30
0.5
0
0.15 0
.45
0.1
5
0.5
0
0.15 0.4
5
0.45
0.30
0.40
0.60 0.45
0.5
5
0.55
0.45 0.50
0.500.5
0
0.60
0.600.50 0.5
5
0.65
0.55
0.55 0.60
0.60 0.65
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
010
0.000.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.951.00
Figure 4. The distribution of oil saturation for different steam in the same reservoir
IV. APPLICATIONS
Large-scale cyclic wet steam stimulation was carried
out in GQ 3 zone of Henan Oilfield in February 2005.
Until February 2010, the cumulative cycles of cyclic wet
steam stimulation reached 261 in the zone. The
cumulative mass of wet steam injection was
20.4464×104t. The cumulative oil production was
7.7742×104t. The water recovery percentage was 100.9%.
The oil-steam ratio was 0.30. In August 2009, cyclic
superheated steam stimulation was carried out in GQ 3
zone. It was divided into two types that were respectively
the superheated steam injection after cyclic wet steam
stimulation in the old layer and the direct cyclic
superheated steam stimulation in a new oil layer. At
present, the cumulative cycles of cyclic superheated
steam stimulation have been up to 52. The cumulative
cycles were 37 in the old oil layer. The cumulative cycles
were 15 in the new oil layer. The cumulative mass of
superheated steam was 3.3178×104t after cyclic wet
steam stimulation in the old oil layer. The cumulative oil
production was 1.2661×104t. Compared with the former
cyclic wet steam stimulation, the oil-steam ratio was up
to 0.35 from 0.30 and the water cut decreased to 69.52%
from 82.12%, which showed that cyclic superheated
steam stimulation obviously improved development
effect of old oil layer. The development effect was better
in the new layer than the old layer. The oil-steam ratio
was up to 0.52 during cyclic superheated steam
stimulation in the new layer. The results are tabulated in
Table II.
TABLE II. THE COMPARISON OF DEVELOPMENT EFFECT BETWEEN
WET STEAM AND SUPERHEATED STEAM
Stage
Total
number
of cycles
Total well
number
Cumulative
steam
injection (×104t)
Cumulative
oil
production (×104t)
Water cut
(%)
Oil-
steam
ratio (t/t)
Wet steam stimulation
261 34 20.4464 7.7742 72.63 0.30
Superheated
steam
stimulation
Old
layer 37 18 2.6276 0.9086 70.58 0.35
New
layer 15 11 0.6902 0.3575 66.44 0.52
Total 52 29 3.3178 1.2661 69.52 0.38
V. CONCLUSIONS
The recovery mechanisms from superheated steam
injection mainly include distillation effect of superheated
steam, oil viscosity reduction due to high temperature,
thermal expansion of heavy oil, larger sweep area and
higher displacement efficiency of superheated steam.
The cumulative oil production of cyclic superheated
steam stimulation is obviously higher than that of cyclic
wet steam stimulation when the same mass of steam is
injected into heavy oil reservoirs. The cumulative oil
production gradually increases as superheated degree
increases, but the incremental oil degree becomes low
when superheated degree is over 20oC. For the same mass
of steam, heating area and steam chamber are lager after
injecting superheated steam than wet steam. Meanwhile,
the distillation effect is stronger after superheated steam
due to the higher temperature and the lower pressure
resulting in more significant incremental oil production.
Under a condition of the same oil production, the
steam consumption was lower after injecting superheated
steam than wet steam in the same heavy oil reservoirs.
Superheated steam can carried more heat and its specific
volume is larger, which can effectively enlarge sweep
volume and save large amount steam injection.
ACKNOWLEDGMENT
Journal of Industrial and Intelligent Information Vol. 2, No. 3, September 2014
1922014 Engineering and Technology Publishing
The study was supported by National Natural Science
Foundation of China (51104165), the Research Fund for
the Doctoral Program of Higher Education
(20110007120003) and the Science Foundation of China
University of Petroleum, Beijing (KYJJ2012-02-19).
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and Exhibition, Beijing, China, June 8-10, 2010. [3] X. H. Wu, B. J. Dong, A. Z. Xu, Z. F. Fei, and R. F. Wang,
“Superheated steam huff and puff to revivify a marginal pre-salt
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Zhanxi Pang obtained a PhD (2008) from the
Faculty of Petroleum Engineering in China University of Petroleum, Beijing. His PhD
thesis “Seepage Mechanisms & Applications
of Steam (Gas) Foam Compound Flooding” is researching the EOR mechanisms of thermal
foam compound flooding and flowing characteristics of foams in porous media.
Based on the basic theory of seepage
mechanics, experimental researches and theoretic analysis were employed to research into foam shearing
characteristics, flowing characteristics and blocking ability of foams in porous media, flooding mechanisms of foams and thermal foams, and
technology of injection foam anti-water-coning. He currently works at
the Faculty of Petroleum Engineering in China University of Petroleum, Beijing.
Chengxiang Qi graduated from the China
University of Geosciences in 2003, where he
studied many courses about petroleum engineering. Then he became a petroleum
engineer at Section of Reservoir Development in CNOOC Iraq Limited. His expertise is in
the field of reservoir engineering and
numerical simulation of thermal recovery in heavy oil reservoirs. He has published more
than 10 refereed journal papers.
Journal of Industrial and Intelligent Information Vol. 2, No. 3, September 2014
1932014 Engineering and Technology Publishing
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