1. Research on Asphaltene Deposition During the Process of CO2 Flooding
For IEA EOR Meeting
CNPC
Research on Asphaltene Deposition During the Process of CO2 Flooding
Huang Lei1 Shen Pingping1 Jia Ying2 Li Shi1 1.State Key Laboratory of EOR (Research Institute of Petroleum Exploration and Development,Petrochina) 2.Exploration and Production Research Institute, Sinopec

2. content 1、Research Background
CNPC
1、Research Background
2、Asphaltene Precipitation Experiment study for CO2 Injection
3、Asphaltene Precipitation Model for CO2 Injection Process
4、Compositional simulator Considering Asphaltene Deposition
5、Conclusion

3. Research Background Asphaltene deposition in the well hole
CNPC
Asphaltene deposition in the well hole
Asphaltene deposition in the pipe line

4. Asphaltene Precipitation Asphaltene Deposition
Research Background
CNPC
Two Basic Concept
Asphaltene
Resins
aromatics
Alkanes
CO2
CO2 Injection
Asphaltene Precipitation
Asphaltene Deposition
Asphaltene Precipitation: Asphaltene component to be seperated from oil and get together to form another phase different from oil phase
Asphaltene deposition: the process of precipitated asphaltene settling onto the surface of porous media

5. content 1、Research Background
CNPC
1、Research Background
2、Asphaltene Precipitation Experiment study for CO2 Injection
3、Asphaltene Precipitation Model for CO2 Injection Process
4、Compositional simulator Considering Asphaltene Deposition
5、Conclusion

6. Asphaltene Precipitation Experiment study for CO2 Injection
CNPC
The Basic Properties and Composition of Experiment Oil
Sampling
Separator Sampling
Reservoir Pressure（MPa） 32
Reservoir Temperatue（℃）
110
Bubble Point（MPa） 4
GOR（m3/m3）
12.9
FVF
1.088
(g/cm3)
0.8219
(mPa.s)
7.02
Dead Oil Density (g/cm3)
0.886
CO2
0.34
C1+N2
11.26
C2～C10
23.43
C11+
64.97
Wax of Dead oil (％)
24.69
Asphaltene of Dead oil (％)
16.79
Evaluation
Representative

7. Asphaltene Precipitation Experiment study for CO2 Injection
CNPC
Equipment for precipitation onset ooint measure
激光法测试固相析出点
-30～180℃ 0～70MPa
电磁搅拌 程序控温 样品筒可视 在线过滤
沥青质 石蜡 水合物

8. Asphaltene Precipitation Experiment study for CO2 Injection
CNPC
Equipment for precipitate quantity measure
注：1-3.手动高压泵 高压阀门 P1-P5.压力表
A.主平衡釜 B.副釜 C.转样釜 D.空气恒温浴 E.石油醚洗瓶

9. Asphaltene Precipitation Experiment study for CO2 Injection
CNPC
20.0MPa
20.0MPa
23.0MPa
26.0MPa
26.0MPa
29.0MPa
32.0MPa
35.0MPa
29.0MPa
32.0MPa
35.0MPa
PTL response of asphaltene Precipitation process

10. Asphaltene Precipitation Experiment study for CO2 Injection
CNPC
Result of Asphaltene Precipitation Experiment
Onset line
saturation line
Critical point
CO2,mole %
injection
pressure
MPa
CO2 content
@onset
mol%
@vapering
Asphaltene in oil
wt%
Asphaltene Precipitation
noCO2
16.79
23.00
0.27
0.60
11.32
5.47
26.00
0.30
0.64
10.31
6.48
29.00
0.33
0.68
9.85
6.94
32.00
0.36
0.71
9.52
7.27
35.00
0.39
0.73
9.13
7.66

11. content 1、Research Background
CNPC
1、Research Background
2、Asphaltene Precipitation Experiment study for CO2 Injection
3、 Asphaltene Precipitation Model for CO2 Injection Process
4、Compositional simulator Considering Asphaltene Deposition and its Application
5、Conclusion

12. Asphaltene Precipitation Model for CO2 Injection Process
CNPC
Presumption
Precipitated asphaltene is composed of heavy polarity and non-ideal molecules, which is solid-like precipitated liquid with strong viscosity under reservoir condition. Thus, equation of state incorporating association （AEOS）is used to describe the phase behavior of asphaltene.
Ignoring resin component，precipitated asphaltene is only composed of asphaltene component.
Asphaltene components do not behave association in oil phase.
During the process of asphaltene precipitation, no crystal formed.

13. Asphaltene Precipitation Model for CO2 Injection Process
CNPC
Compressible factor of asphaltene
Because precipitated asphaltene is composed of heavy polarity and non-ideality molecules, the compressible factor of association compound established by Anderko is introduced to describe the non-ideality of precipitated asphaltene
where

14. Asphaltene Precipitation Model for CO2 Injection Process
CNPC
Fugacity Calculation for Asphaltene Phase

15. Asphaltene Precipitation Model for CO2 Injection Process
CNPC
vapor/liquid/asphaltene equilibrium model:
where

16. Asphaltene Precipitation Model for CO2 Injection Process
CNPC
Phase stability analysis of precipitated asphaltene:
Judgement of asphaltene precipitation is as follows:
if ，asphaltene would precipitate ；
if ，asphaltene would not precipitate ；
if ，asphaltene begin to precipitate 。
Where is content of heavy components in oil.

17. Asphaltene Precipitation Model for CO2 Injection Process
CNPC
Regression Result for Asphaltene Pricipitation onset point
CO2,mole %
cal.Pb point
cal.onset line
cal.disappearance line
expl.onset line
exp.Pb line
critical point
Pressure,MPa

18. Asphaltene Precipitation Model for CO2 Injection Process
CNPC
the relationship between asphaltene precipitation and CO2 mole percent at fixed pressure
the relationship between asphaltene precipitation, gas phase mole percent and pressure at varied CO2 mole percent
Asphaltene Precipitation,wt%
Gas mole%
CO2,mole%
pressure,MPa
When pressure is constant, precipitated asphaltene increases with the increase of injected CO2 before system reaches saturation. Precipitated asphaltene reaches maximum near saturation point, and then decreases with the increase of CO2.
When the CO2 content of a system are constant, precipitated asphaltene reaches maximum near saturation pressure.
The higher system pressure, the more maximum quantities of precipitated asphaltene.

19. content 1、Research Background
CNPC
1、Research Background
2、Asphaltene Precipitation Experiment study for CO2 Injection
3、Asphaltene Precipitation Model for CO2 Injection Process
4、Compositional simulator Considering Asphaltene Deposition
5、Conclusion

20. Compositional simulator Considering Asphaltene Deposition
CNPC
Conservation Equation for Component i
Conservation Equation for Water
Conservation Equation for Oil and Gas
where，

21. Compositional simulator Considering Asphaltene Deposition
CNPC
Precipitated asphaltnene is made up of three parts：deposit onto the porous media surface through adsorption ； deposit through mechanical entrapment ；suspended in the oil phase
adoption by unit rock volume
surface adsorption by unit rock mass follows a Langmuir isotherm ：
suspended content in oil phase：
mechanical entrapment ：

22. Compositional simulator Considering Asphaltene Deposition
CNPC
Plugging Equations
Using following equations established by Cernansky &Siroky（1985）to describe plugging process

23. Recovery factor matching for core flooding
Compositional simulator Considering Asphaltene Deposition
CNPC
Recovery factor matching for core flooding
Sequnial
Core length(cm)
Perm
( mD )
Soi(％)
Pex(MPa)
dp(MPa)
Injection PV
Exp. Re
(%)
New method
Cal. Re
Conventional methed 1
43.16
8.92
0.5494 19 5
3.31
59.76
58.47
63.28 2
42.85
8.91
0.5527 24
6.4
3.11
64.38
64.12
67.85 3
45.82
8.69
0.5561 29 8
78.07
80.13
82.77 4
0.5524 34 10
2.88
79.24
82.04
84.32

24. Compositional simulator Considering Asphaltene Deposition
CNPC
0.1HCPV
0.2HCPV
0.3HCPV
0.4HCPV
Asphaltene precipitated,wt%
Sg,%
distance
Asphaltene deposition front is consistent with gas front, which indicates that CO2 injection leads to asphaltene pricipitate

25. Compositional simulator Considering Asphaltene Deposition
CNPC
As pressure rises，more asphaltene deposition in core.

26. content 1、Research Background
CNPC
1、Research Background
2、Asphaltene Precipitation Experiment study for CO2 Injection
3、Asphaltene Precipitation Model for CO2 Injection Process
4、Compositional simulator Considering Asphaltene Deposition
5、Conclusion

27. Conclusion AEOS can describe asphaltene precipitation behavior.
CNPC
AEOS can describe asphaltene precipitation behavior.
For a fixed pressure system, precipitated asphaltene increases with the increase of injected CO2 before system reaches saturation, then precipitated asphaltene decreases with the increase.
When system composition is fixed, precipitated asphaltene reach its climax near saturation pressure.
Asphaltene precipitation should be considered in CO2 injection process of high asphaltene content oil.
Asphaltene deposition front is consistent with CO2 front.
As pressure rises，more asphaltene deposition lefted in core.