1. Qatar Carbonates and Carbon
Storage Research Centre
Rheology and Phase Behaviour of
Carbon Dioxide and Crude Oil
Mixtures
Ruien Hu
Dr. Edo Boek
Dr. John Crawshaw
Prof. J. P. Martin Trusler
CSChE 2015
2. Background
CO2 Crude Oil Mixtures
ηmix
Viscosity
Temperature
CompositionPressure
• Kariznovi, Nourozieh, &
Abedi, 2011
• Mehrotra, Monnery, &
Svrcek, 1996
• Lansangan, 1993
• Kokal & Sayegh, 1993
• Miller & Jones, 1981
Literature Review
Shear Rate
2
3. 1. How does CO2
reduce the crude oil
viscosity?
2. Newtonian or non-
Newtonian?
3. How does the
phase behaviour
relate to the
viscosity change?
Viscosity
Temperature
CO2 Composition
Pressure
Shear Rate
Objectives
3
4. Properties Value
Density at 15°C (g/cm3) 0.983
API Gravity 9.28
Viscosity at 40°C (mm2/s) 20020
n-heptane Asphaltenes (% wt) 16.1
Zuata Crude Oil
Samples
4
5. CO2 + Crude Oil
70% Crude
Oil
30%
Toluene
90% Crude
Oil
10%
Toluene
100%
Crude Oil
Rheology
Phase
Behaviour
T = 50 °C
P ≤ 220 bar
Experiments
5
8. 100% Crude Oil at 50 °C
Results
1 bar
100 bar
100%
Crude
Oil
8
9. 9
100% Crude Oil at 50 °C
Results
100%
Crude
Oil
P ≥ 60 bar
1 bar
20 bar
40 bar
10. 100% Crude Oil at 50 °C
Results
220 bar
120 bar
100%
Crude
Oil
10
11. 100% Crude Oil at 50 °C
Results
10 bar 20 bar1 bar 30 bar 40 bar 50 bar 60 bar 70 bar 80 bar 90 bar
120 bar 140 bar 160 bar 180 bar 200 bar 220 bar
100 bar
100%
Crude
Oil
11
12. 90% Diluted Crude Oil at 50 °C
1 bar
90 bar
Results
90%
Crude
Oil
10%
Toluene
12
13. 90% Diluted Crude Oil at 50 °C
220 bar
100 bar
Results
90%
Crude
Oil
10%
Toluene
13
14. 90% Diluted Crude Oil at 50 °C
Results
1 bar 10 bar 20 bar 30 bar 40 bar 50 bar 60 bar 70 bar 80 bar 90 bar 100 bar
90%
Crude
Oil
10%
Toluene
120 bar100 bar 140 bar 160 bar 180 bar 200 bar 220 bar
14
16. Shear thinning
30 bar → 60 bar
70% Diluted Crude Oil at 50 °C
1 bar
80 bar
Results
Sample 1
70%
Crude Oil
30%
Toluene
16
17. 70% Diluted Crude Oil at 50 °C
220 bar
100 bar
Results
Sample 1
70%
Crude Oil
30%
Toluene
17
18. 70% Diluted Crude Oil at 50 °C
1 bar
80 bar
Results
70%
Crude Oil
30%
Toluene
Sample 2 18
19. 70% Diluted Crude Oil at 50 °C
220 bar
100 bar
Results
70%
Crude Oil
30%
Toluene
Sample 2 19
20. 70% Diluted Crude Oil at 50 °C
Results
1 bar 10 bar 20 bar 30 bar 40 bar 50 bar 60 bar 70 bar 80 bar
120 bar 140 bar 160 bar 180 bar 200 bar 220 bar100 bar
70%
Crude Oil
30%
Toluene
Sample 2 20
21. Non-Newtonian Effect
• The shear thinning effect in the original heavy crude oil is
eliminated by the CO2 dissolution.
• CO2 dissolution causes the shearing thinning effect in 70% diluted
crude oil, but not the 90% one.
• Sampling issue.
Viscosity Pressure Dependence
• The crude oil viscosity reaches a minimum when it mixes with CO2.
Phase Behaviour
• CO2 dissolved causes the swelling of oil phase.
• A second hydrocarbon rich phase is observed in more diluted crude
oil, but not in others.
Conclusions
21
24. 100% Crude Oil at 50 °C
Results
100%
Crude
Oil
24
25. 90% Diluted Crude Oil at 50 °C
Results
90%
Crude
Oil
10%
Toluene
Oil expands
Oil shrinks
25
26. 70% Diluted Crude Oil at 50 °C
Results
70%
Crude Oil
30%
Toluene
Sample 2
One
Phase
Multiple
Phases
26
Editor's Notes
It is well known that CO2 can significantly reduce the crude oil viscosity. This effect has been widely used in enhanced oil recovery. Effort has been made to measure the change of crude oil viscosity by CO2 dissolution. Traditionally people study this subject as a classic transport properties problem, measuring the viscosity at a fixed shear rate, and focus on the relationship between viscosity and temperature, pressure and composition.
With all the measurement performed, we realise that the visual evidence of the phase behaviour change of the CO2 and crude oil mixtures could be extremely helpful to understand the phenomena we seen in the viscosity and solubility measurements. Therefore, we decide to build a view cell system to observe the phase behaviour of CO2 and crude oil mixture. The view cell is placed in an oven, and a borescope mounted with a camera is used to observe the phase behaviour through the window on the view cell. This system is now under construction.
This graph shows the viscosity of the 90% diluted crude oil at shear rate from 40 to 500 1/s and at 50 degree C. The dash line represents the minimum shear rate for each viscosity. The viscosity measurement at shear rate lower than that limit will cause too much noise in the measurement because of the bearing friction. In the reliable data region, the highest point set represents the viscosity of the diluted crude oil at 1 bar. The rest of the point sets represent the viscosity of the CO2 saturated mixture at different pressure level. The horizontal line of the each point set shows that the diluted crude oil and its mixtures with CO2 behave as a Newtonian fluid in the studied shear rate range.
The measurement of the 70% diluted crude oil shows a more interesting result. The measurement is performed at 50 degree C for shear rate from 35 to 250 1/s. Once again, the dash line represents the minimum shear rate of each viscosity. The highest point set is the viscosity of the diluted crude oil at 1 bar, and the rest of them are for the CO2 saturated mixture. As we can see, from 1 to 20 bar the fluid is Newtonian. Then for pressure from 30 to 60 bar, the fluid illustrates a shear thinning effect with a Newtonian platform at high shear rate. Finally, when pressure is beyond 60 bar, the fluid behaves as a Newtonian fluid again, demonstrated by the horizontal lines. Such non-Newtonian behaviour has not been reported in literature. My colleague Christine found that the onset point of the asphaltene precipitation is between 80 to 100 bar. It means the cause of the non-Newtonian effect is not the asphaltene. The cause is speculated to be the generation of an emulsion by the asphaltene components when CO2 dissolves into the crude oil. This theory needs to be investigated with the view cell system we are building now.
