Experimental and mathematical modeling of foamy-oil evolution and flow in the primary production and CO₂-based cyclic solvent injection

In this thesis, first, experimental and numerical studies were conducted to differentiate solvent exsolution (i.e., the solution gas becomes the dispersed gas) and liberation (i.e., the dispersed gas becomes the free gas) processes from the heavy oil-CO2/CH4/C3H8 system in bulk fluids and porous media. Experimentally, two series of constant-composition-expansion (CCE) tests in a PVT cell and differential fluids production (DFP) tests in a sandpacked physical model were performed. The experimental results showed that the solvent exsolution from each heavy oil-solvent system in the porous media occurred earlier than that in the bulk fluids. In addition, the nucleation of CH4 bubbles was found to be more instantaneous than that of CO2/C3H8 bubbles. Numerically, a robust kinetic reaction model in the commercial CMG-STARS module was utilized to simulate the solvent exsolution and liberation processes in the CCE and DFP tests. It was found that CH4 was beneficial for foam-oil flow because it was exsolved from the heavy oil most easily in the porous media and was also the most difficult to be liberated from the heavy oil. Second, when to start the CO2-based cyclic solvent injection (CO2-CSI) post the primary production, namely the timing of CO2-CSI, was studied by conducting a series of eight experimental tests, of which five major production data were measured by using the DFP method. The optimum ending primary production pressure (Pe) was found to be the lowest test pressure. It was also found that the primary production with a lower ending production pressure (Pe) had three distinct fluid production trends: single-phase flow (Ipp), foamy-oil flow (IIpp), and foamy-oil flow + free-gas flow (IIIpp). Moreover, three possible fluid production trends were found in the early cycles of CO2-CSI: free-gas flow (ICSI), foamy-oil flow + free-gas flow (IICSI), and free-gas flow (IIICSI). Third, a theoretical study was conducted to investigate the solvent exsolution and liberation processes in the porous media. Specifically, the material balance equation (MBE) and the free-gas production data measured through the DFP method were utilized to calculate the amounts of the solution gas, evolved gas, dispersed gas and free gas in the sandpacked physical model. In the solvent exsolution, it was found that the amount of the evolved gas in the sandpacked model was increased steadily until it reached a stable value. Furthermore, the amount of the evolved gas in the sandpacked model at the end of the primary production was similar to that at the beginning of the free-gas production. In the solvent liberation, a threshold free-gas saturation existed so that the maximum amount of the free gas was kept in the sandpacked model. Fourth, two numerical simulation models were developed to simulate the foamy-oil flow. In the first model (Model A), two kinetic reaction models were used to describe the solvent exsolution and liberation, whereas in the second model (Model B), bubble nucleation, growth, liberation and break-up were considered. It was found from Model A that the solvent exsolution and liberation were more difficult in the early and late production periods than those in the middle period. The obtained bubble size distribution from Model B shows that the bubble sizes were increased rapidly at the beginning and that the bubble number was increased significantly over time. In addition, bubble break-up caused two peak values of the bubble number in the bubble size distribution. Furthermore, it was found that a larger integral area under the bubble size distribution indicated a stronger foamy oil, whereas smaller radii corresponding to the peak values of the bubble number meant a more stable foamy oil.

Name thesis:degree_name

Doctor of Philosophy (PHD)

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Engineering - Petroleum Systems

Grantor dc:publisher

Faculty of Graduate Studies and Research, University of Regina

Year dc:date.issued

2025

Author dc:creator

• Zou, Wei

Advisor dc:contributor.advisor

• Gu, Yongan (Peter)

Committee members dc:contributor.committeemember

• Yang, Daoyong (Tony)
• Jia, Na (Jenna)
• Yao, Yiyu

Language dc:language.iso

en

DOI

https://doi.org/10.82465/4100

OAI identifier oai:identifier

oai:uregina.scholaris.ca:10294/17102