Doris Gonzalez1,2, Francisco Vargas1, George Hirasaki1 and Walter Chapman1

1
A Modeling Study of CO2 Induced Asphaltene
Precipitation
Doris Gonzalez1,2, Francisco Vargas1, George
Hirasaki1 and Walter Chapman1
1 Chemical and Biomolecular Engineering
Department, Rice University, Houston, Texas,
USA 2 Data Quality Group, Schlumberger, Houston,
Texas, USA
Department of Chemical and Biomolecular
Engineering
Rice University
Processes in Porous Media Consortium, March 26,
2008
2
Objectives

• Predict the effect of CO2 addition on APO using
  PC-SAFT EoS (Infochem software)
• Demonstrate that CO2 behaves differently compared
  to N2 and Methane
• Provide a thermodynamic explanation of this
  phenomenon

3
Outline

• The PC-SAFT equation of state
• Case 1 Asphaltene Precipitation Prediction for a
  live oil (Fluid A) effect of CO2, N2 and Methane
  addition
• Case 2 Asphaltene Precipitation Prediction for a
  stock tank oil
• Thermodynamic Analysis of CO2 behavior
• Conclusions

4
Outline

• The PC-SAFT equation of state
• Case 1 Asphaltene Precipitation Prediction for a
  live oil (Fluid A) effect of CO2, N2 and Methane
  addition.
• Case 2 Asphaltene Precipitation Prediction for a
  stock tank oil
• Thermodynamic Analysis of CO2 behavior
• Conclusions

5
The PC-SAFT EoS
Chapman, Jackson, and Gubbins, Mol. Phys. 65,
1057 (1988). Gross Sadowski, Ind. Eng. Chem.
Res., 40, 1244-1260 (2001)
6
The PC-SAFT EoS
Experimental / Field Data
Oil characterization
Asphaltene characterization

• SARA / composition
• Density
• Bubble point

• Precipitation onset

PC-SAFT Parameters
si, ei/k, mi
7
Case 1 Fluid A
Parameters characterization
PNA PAH
8
Outline

• The PC-SAFT equation of state
• Case 1 Asphaltene Precipitation Prediction for a
  live oil (Fluid A) effect of CO2, N2 and Methane
  addition
• Case 2 Asphaltene Precipitation Prediction for a
  stock tank oil
• Thermodynamic Analysis of CO2 behavior.
• Conclusions

9
Case 1 Fluid A
Background

• Reservoir T 296 F (147C)
• The asphaltenes are unstable
• IOR Study pressure maintenance using N2
• Significant risk of asphaltene precipitation
  during N2 injection process?

A.K.M. Jamaluddin, N. Joshi, F. Iwere, Gurpinar,
SPE 74393 (2001)
10
Case 1 Fluid A
SAFT Simulation
Precipitation onset
Stable region
Unstable region
Bubble point
VLE
Temperature, F
Exp. data from A.K.M. Jamaluddin, N. Joshi, F.
Iwere, Gurpinar, SPE 74393 (2001)
11
Case 1 Fluid A N2 injection
Another View, Composition Effects
Stable region
Unstable region
Precipitation onset
Bubble point
VLE
Exp. data from A.K.M. Jamaluddin, N. Joshi, F.
Iwere, Gurpinar, SPE 74393 (2001)
12
Case 1 Fluid A
N2 Injection AOP Live oil A
Base Case
Temperature, F
Gonzalez, Vargas, Hirasaki, and Chapman. Energy
and Fuels, 22, 2 (2008)
13
Case 1 Fluid A
Inject 5 mol N2
5 mol N2
Temperature, F
Gonzalez, Vargas, Hirasaki, and Chapman. Energy
and Fuels, 22, 2 (2008)
14
Case 1 Fluid A
Inject 10 mol N2
10 mol N2
Temperature, F
Gonzalez, Vargas, Hirasaki, and Chapman. Energy
and Fuels, 22, 2 (2008)
15
Case 1 Fluid A
What about Methane?
Temperature, F
Gonzalez, Vargas, Hirasaki, and Chapman. Energy
and Fuels, 22, 2 (2008)
16
Case 1 Fluid A
Inject 5 mol Methane
5 mol CH4
Temperature, F
Gonzalez, Vargas, Hirasaki, and Chapman. Energy
and Fuels, 22, 2 (2008)
17
Case 1 Fluid A
Inject 10 mol Methane
10 mol CH4
Temperature, F
Gonzalez, Vargas, Hirasaki, and Chapman. Energy
and Fuels, 22, 2 (2008)
18
Case 1 Fluid A
What about using CO2?
Temperature, F
Gonzalez, Vargas, Hirasaki, and Chapman. Energy
and Fuels, 22, 2 (2008)
19
Case 1 Fluid A
Inject 5 mol CO2
5 mol CO2
Temperature, F
Gonzalez, Vargas, Hirasaki, and Chapman. Energy
and Fuels, 22, 2 (2008)
20
Case 1 Fluid A
Inject 10 mol CO2
10 mol CO2
Gonzalez, Vargas, Hirasaki, and Chapman. Energy
and Fuels, 22, 2 (2008)
Temperature, F
21
Case 1 Fluid A
Compare Injected Gases
Exp. data from A.K.M. Jamaluddin, N. Joshi, F.
Iwere, Gurpinar, SPE 74393 (2001)
22
Outline

• The PC-SAFT equation of state
• Case 1 Asphaltene Precipitation Prediction for a
  live oil (Fluid A) effect of CO2, N2 and Methane
  addition
• Case 2 Asphaltene Precipitation Prediction for a
  stock tank oil
• Thermodynamic Analysis of CO2 behavior.
• Conclusions

23
Case 2 Stock tank oil South America
CO2 injection, Temperature effect
Temperature, F
Exp. Data from S. Verdier, H. Carrier, S.
Andersen, J.L. Daridon. Energy Fuels. 20,
1584-1590 (2006)
24
Case 2 Fluid South America
CO2 titration at high pressure
Temperature, F
Exp. Data from S. Verdier, H. Carrier, S.
Andersen, J.L. Daridon. Energy Fuels. 20,
1584-1590 (2006)
25
Outline

• The PC-SAFT equation of state
• Case 1 Asphaltene Precipitation Prediction for a
  live oil (Fluid A) effect of CO2, N2 and Methane
  addition
• Case 2 Asphaltene Precipitation Prediction for a
  stock tank oil
• Thermodynamic Analysis of CO2 behavior
• Conclusions

26
Thermodynamic Analysis Model Live Oil
Pressure, psia
Temperature, F
Gonzalez, Vargas, Hirasaki, and Chapman. Energy
and Fuels, 22, 2 (2008)
27
Thermodynamic Analysis Model Live Oil
Adding CO2
Pressure, psia
Temperature, F
Gonzalez, Vargas, Hirasaki, and Chapman. Energy
and Fuels, 22, 2 (2008)
28
Thermodynamic Analysis Model Live Oil
Solubility Implications
Asphaltene
Model oil
CO2
Methane
Temperature, F
Gonzalez, Vargas, Hirasaki, and Chapman. Energy
and Fuels, 22, 2 (2008)
29
Outline

• The PC-SAFT equation of state
• Case 1 Asphaltene Precipitation Prediction for a
  live oil (Fluid A) effect of CO2, N2 and Methane
  addition.
• Case 2 Asphaltene Precipitation Prediction for a
  stock tank oil
• Thermodynamic Analysis of CO2 behavior.
• Conclusions

30
Conclusions

• CO2 addition to an oil can increase or decrease
  its asphaltene instability depending on T
• This behavior is different to what we observe for
  methane and N2
• PC-SAFT EoS accurately model the phase behavior
  of oils containing asphaltene and dissolved gases
• The CO2 behavior can be explained using the
  concept of solubility parameter

31
Acknowledgements
Deepstar Schlumberger Chevron ETC CHBE Department
at Rice University
32
A Modeling Study of CO2 Induced Asphaltene
Precipitation
Doris Gonzalez1,2, Francisco Vargas1, George
Hirasaki1 and Walter Chapman1
1 Chemical and Biomolecular Engineering
Department, Rice University, Houston, Texas,
USA 2 Reservoir Fluid Advisory Group,
Schlumberger, Houston, Texas, USA
Department of Chemical and Biomolecular
Engineering
Rice University
Processes in Porous Media Consortium, March 26,
2008