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A Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Petroleum Systems Engineering, University of Regina. xx, 257 p. It has been suggested that Cyclic Solvent Injection (CSI) is a highly promising technique to recover heavy oil resources at which other recovery techniques are not economically or efficiently available. Therefore, it is necessary to conduct experimental and mathematical studies on the CSI for effective heavy oil recovery purposes. Experimental and data regression studies have been conducted to investigate the effects of the wormhole on the CSI. Nine tests were completed using three sand-pack physical models with different dimensions. Experimental results suggest that the oil production can be divided into two phases: solvent chamber rising phase and solvent chamber spreading phase. The average production rate in the solvent chamber rising phase is proportional to the wormhole length, while the average production rate in the solvent chamber spreading phase does not change much with the wormhole length. In addition, a relation of the oil production rate to the drainage height is obtained by regression analysis and verified with a different experiment. It is suggested that for a rectangular model, the oil production rate in the chamber rising phase is proportional to h1.1667. Experimental study of effects of pressure decline rate on the CSI has been performed. Twelve tests with ten decline rates through linear and non-linear pressure-drawdown methods were conducted. Results of optimizing the pressure decline rate indicated that the pressure decline rate plays a primary role in the CSI by affecting solvent chamber growth, foamy oil flow performance in Phase 1, and pressure drop force in Phase 2. Different driving mechanisms in different phases lead to different optimum pressure decline rates. Comparison of two pressure-drawdown methods suggests that the main difference between the non-linear pressure-drawdown method and linear pressuredrawdown method is that the former cannot provide a continuous driving force for diluted oil as well as the latter. The effect of the intermittent driving force is much more significant in Phase 2. Therefore, production performance of tests of pressure-drawdown linearly was generally better than that of tests of pressure-drawdown non-linearly. A linear material balance equation of CSI has been proposed to obtain the recovery factor of diluted oil. It is successfully used to obtain the recovery factor of diluted oil of each cycle for a well-designed CSI test in a rectangular physical model (80×40×20 cm3). The relation of the solution-gas oil ratio and the diluted oil formation volume factor with pressure under non-equilibrium state are obtained through linear regression based the material balance equation. They are successfully verified through experimental data of a CSI test in a cylindrical model. Results indicate that the efficiency of oil dilution increases from 4.75% to 10.70% before the Cycle 10. Then it slightly varies from 10% to 16.25% till the Cycle 25. It is dramatically decreased 10.11% in the last five cycles. For first three cycles, the diluted oil recovery factor is up to 40% due to extended production time. Then it almost keeps around 32% till the Cycle 25. Three mixture solvent with the decline rate of 12.5 kPa/min ,5 kPa/min and 1 kPa/min have been conducted. Knowledge of production performance of mixture solvent CSI tests is obtained through the comparison of mixture solvent tests with different decline rate and the comparison between mixture and pure solvent tests. Pure solvent tests had larger recovery factor and average oil production per cycle than mixture solvent tests. The asphaltene precipitation and production time significantly impacted the recovery factor of diluted oil in mixture solvent tests. Student yes

A Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements for the Degree of Master of Applied Science in Petroleum Systems Engineering, University of Regina. xii, 103 p. As the demand of crude oil increases sharply nowadays, heavy oil, an unconventional liquid hydrocarbon representing more than 70% of the world’s total oil, needs to be further produced in the coming decades. Although some laboratory experiments have been conducted to find out the mechanism of foamy oil during pressure depletion processes. There are still some difficulties in understanding the characteristics of foamy oil flow in Cold Heavy Oil Production (CHOP). Large amounts of heavy oil samples used in previous studies were mixed with methane, carbon dioxide and butane. Only several studies were conducted under heavy oil-mixture solvent systems. Therefore, it is of great significance to carry out some experiments to perceive the foamy oil flow characteristics with its influencing factors in heavy oil-mixture solvent (CO2-C3H8) systems so as to get better recovery factors in primary production. In this study, four pressure depletion tests were conducted in 1D sand pack model to find out factors affecting the duration of foamy oil flow and recovery factors were obtained as the result. Firstly, all the conditions were the same except for the decline rate (-1, -2, -6, -12 kPa/min). Secondly, the optimized depletion rate was applied into the next stage experiments which was used to understand the length effect on foamy oil flow characteristics. Once all the depletion tests had been completed, another four post-CHOPS CSI tests were conducted to find out whether gravity can take effect on the oil recovery factors. Results show that in CO2-C3H8 mixture solvent-heavy oil system, oil recovery factor increases as the depletion rate becomes larger. Furthermore, compared with pure solvent heavy oil system, mixture solvent shows better during depletion tests. Besides, results show that there is a positive correlation between oil recovery factor and gravity. Last but not least, results from the pressure depletion tests indicate that pressure gradient will become smaller at the end as the model length increases. In the oil field, pressure gradient remains a low level when it is far away from the well bore and that is one reason for low cumulative oil production. Student yes

A Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements for the Degree of Master of Applied Science in Petroleum Systems Engineering, University of Regina. xiv, 95 p. With vast potential reserves of heavy oil, the research on heavy oil has been the hottest topic over the decades. Foamy oil flow occurs in primary production of heavy oil reservoirs with unexpected high oil recovery factor. Studying on foamy oil mechanisms and flow behaviors helps enhancing oil recovery. Lots of experimental researches have been conducted to investigate on improving foamy oil flow efficiency. Pressure depletion rate has been proven to be one of the most significant parameters that affects foamy oil flow. However, the other factors that influence foamy oil such as reservoir temperature, oil viscosity, oil composition, etc. are not fully understood. Therefore, it is of great importance to study the influence of temperatures and oil viscosity on foamy oil flow. In this study, two types of experiment are carried out: (1) the sand-pack pressure depletion test under different temperatures; (2) sand-pack pressure depletion test with different viscous oils. In the first series of experiment, four different temperatures (20℃, 30℃, 40℃, 50℃) are selected to exam the production performance. In the second set of experiment, three heavy oil specimens with different oil viscosities are utilized under the same temperature condition (40℃). Initial gas oil ratio (GOR) is settled the same in all experiments. The experimental results of different temperatures indicate that foamy oil flow is weakened, and oil recovery factor declines with elevating temperatures. However, gas recovery factor increases when temperature rises. It is observed that the higher initial reservoir pressure does not certainly increase oil recovery factor during foamy oil flow. Given a favorable live oil viscosity, oil recovery can reach the optimized value. A new foamy oil behavior is discovered during the study, in which a second foamy oil flow appears during the late-time production. The experimental results of different viscosities showed that, there is an optimal live oil viscosity for foamy oil production because the results give a non-linear relationship between oil recovery factor and oil viscosity. The dead oil viscosity should also be considered when estimating oil recovery performance since oil viscosity is approaching to dead oil viscosity due to the relatively low reservoir GOR after gas is produced. Student yes

A Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements for the Degree of Master of Applied Science in Petroleum Systems Engineering, University of Regina. xvii, 157 p. In the solvent-based heavy oil recovery methods, the cyclic solvent injection (CSI) method has been acknowledged as an effective method with high oil production rate. Oil recovery in pure solvent CSI study is as high as over 70%. However, injection pressure in the pure solvent CSI is limited by the low dew point pressure of hydrocarbon at laboratory ambient temperature condition. In the mixture gas CSI method, although the solvent dew point pressure can be raised at the ambient temperature condition, recovery factor of this method is much lower than that of pure solvent CSI method. Therefore, it is necessary to explore an alternative CSI method which takes advantage of both pure gas-based and mixture gas-based CSI methods. As raising the pure solvent injection temperature can increase the solvent dew point pressure, the idea of hot solvent CSI is experimentally tested in this study. This new type of CSI method is named the cyclic hot solvent injection method (CHSI). In the CHSI laboratory study, hot solvent can reach high initial reservoir pressure. The experimental system consists of a sand-pack model unit, injection unit, production unit and data acquisition unit. Three major topics have been studied concerning CHSI: the comparison between CHSI and the replaceable method of CHSI (the mixture gas CSI method), the comparison between CHSI and the “N-Solv” (hot vapor solvent extraction) method, and temperature sensitivity analysis in CHSI. Experimental results show that, for the first topic, oil recovery of CHSI method is much higher than it is in mixture gas CSI method; for the second topic, oil production performance of CHSI is compared with that II in N-Solv; for the third topic, three solvent injection temperature levels are compared with each other in order to study solvent temperature effect on the oil production performance. Experimental results show that the CHSI method is an effective heavy oil extraction method, because this method is superior to mixture gas CSI method and N-Solv method regarding oil recovery. Oil recovery of CHSI is hardly influenced by solvent injection temperature. However, solvent injection temperature positively affects oil production rate during early CSI production period. Student yes