A series of experiments to measure the water solubility in supercritical nitrogen and carbon dioxide have been conducted at experimental conditions up to 483 K and 134 MPa. The accuracy of the experimental procedure is verified by comparing the water content data of methane in the literature and our experimental data for the methane−water system. In addition, a fugacity−fugacity approach including the cubic-plus-association equation of state (CPA EoS) and a fugacity−activity approach based on the Peng−Robinson EoS and the Henry’s law model are incorporated to predict the water content data of methane, nitrogen, and carbon dioxide. A comparison between our experimental data, literature data, and the results of the fugacity−activity approach shows the reliability of the PR-Henry’s law model for the phase behavior studies of the nitrogen−water system over a wide range of pressure and temperature conditions. However, the CPA equation is not capable of reproducing the high pressure vapor and liquid phase compositions of the water−nitrogen system. The concept of cross-association satisfactorily improves the performance of the CPA equation of state in predicting the water content data of supercritical methane. On the basis of the literature and new measured data in this study, it has been found that the CPA equation better represents the phase behavior of the water−carbon dioxide system if carbon dioxide is considered as a self- and cross-associating molecule.

It is acknowledged that chemical reactions and their kinetics play a major role on the success of both light and heavy oil air injection processes. Historically, Light oil reactions have been characterized mostly using conventional heavy oil kinetics models. However, sensitivity of the reaction kinetics to phase behavior and compositional changes in light oils call for a comprehensive study of kinetics of light oil oxidation. This paper provides a new and comprehensive kinetic model for light oils oxidation/combustion reactions under HPAI, through experimental studies and numerical simulation.For the purpose of this research, a high pressure ramped temperature oxidation reactor (HPRTO) was designed. 15 air injection and nitrogen injection experiments were conducted on the mixture of light oil, water, and core. Based on the data, observations, and understandings achieved during the course of the experimental study, a reaction kinetic model was set up. This primary kinetic model was then incorporated into a thermal numerical simulation model to replicate the behavior of the conducted air injection tests. After fine-tuning of some kinetic parameters against the experimental data, the final proposed model was verified by its successful application to two other different cases.The significant finding of this research, which is the main feature of the proposed kinetic model, was the recognition and characterization of the potential vapor phase combustion reactions during the HPAI process and incorporating them into a light oil kinetics model. The model integrates the hydrocarbon compositional changes and energy generation characteristics of the oxygen addition or so called LTO reactions. Introducing the concept of flammability range into the kinetic model and defining the flammable limits for vapor fuel mixture in this model enables accurate prediction of ignition and exhaustion of the combustion reactions in the vapor phase.Lack of a reliable kinetics model for incorporation into field numerical simulations has been a limiting factor to the prospective vast applications of HPAI as an enhanced recovery method. The kinetics model proposed in this paper, which is supported by extensive experimental data, could successfully predict the oxidation/combustion behavior of two different light oils under the conditions associated with high-pressure air injection tests. The paper also presents a framework for application of the kinetics model to any light oil under HPAI.

Oxidation reactions and their kinetics are acknowledged to have a major impact on the success of air injection-based improved recovery processes. Vaporization of oil has been reported in the literature as a mechanism associated with kinetics of air injection processes; however, the parameters which control the vapor phase oxidation/combustion behavior have not been included in the studies of oxidation kinetics.In order to characterize the vapor phase oxidation/combustion behavior of light oils in high pressure air injection (HPAI) process, an experimental and a follow up numerical study have been conducted on a high pressure ramped temperature oxidation (HPRTO) reactor on a 37 o API crude oil and a pure hydrocarbon.The results of this study indicate that phase equilibrium between the liquid and vapor hydrocarbon and water components has a definite impact on the "flammability range" for vapor phase combustion at given temperature and pressure conditions. The observations also suggest the potential participation of vapor phase oxygen addition reactions in the supply of triggering energy for spontaneous ignition.Given the importance of vapor phase behavior on the amount and distribution of hydrocarbons available for reaction with oxygen, a comprehensive phase behavior study on the selected light oil was performed. The developed phase behavior model was then used in a hypothetical model to study the behavior of the vapor phase under conditions of HPRTO tests. The significance of this model is its capability to predict the theoretical injected-air/fuel ratio of the vapor phase assuming thermodynamic equilibrium.

Accurate density description of saturated liquid and vapor (L-V) phases for the water-CO2 system is important in many fields of engineering and science such as CO2 sequestration, supercritical fluids-based extraction and purification processes, and CO2- related enhanced oil recovery methods. There are only a few studies, mostly dedicated to low pressure and temperature conditions, on densities of equilibrium liquid and vapor phases for this system. Due to paucity of experimental data at high pressure and high temperature conditions, a series of experiments have been performed to measure the density of both liquid and vapor phases of water/CO2 system from 382 K to 478 K and pressures from 3.48 MPa to 129 MPa. In order to measure the mass of water and volume of gas in the vapor phase, in each experiment the vapor phase of an LV equilibrium system is transferred to an equilibrium flash separator equipped with a desiccant and a gasometer. The gas volume is converted to density based on the ideal behavior of gases at standard conditions. The density of the liquid phase is directly measured by a densitometer. In addition, a "Two-fluid Model" consisting of the Cubic-Plus-Association equation of state (CPA EOS) and the Henry's law is implemented in phase equilibrium modeling of this system to predict the density of both phases. A comparison between our experimental data, literature data and the results of the model shows the reliability of this model for density prediction of L-V phases of water-CO2 system over a wide range of pressure and temperature conditions.

During the last two decades HPAI (High Pressure Air Injection) has proven to be a successful recovery method in deep light oil reservoirs. Distillation, flue gas drive and thermal front effects are the most dominant mechanisms associated with oil recovery in HPAI processes. This paper describes the results and observations of an experimental study conducted to characterize distillation, not only as a recovery mechanism but moreover as a phenomenon that impacts the kinetics of light oil combustion in HPAI. Distillation or vaporization-condensation of light fractions of oil in thermal processes, more frequently in steam flooding and in-situ combustion, has been studied since its first recognition in 1960. Compositional effect of distillation on phase behavior of light oils, through stripping, and displacement of light ends through vaporization-condensation has been recognized as important. However, certain aspects of distillation such as the latent heat associated with vaporization of hydrocarbons, type of residual fuel remaining in the liquid phase after progression of an evaporation front, and more importantly the type of fuel transferred to the vapor phase through vaporization, all of which impact the kinetics of light oil combustion, has been missing in HPAI studies. This study aims to shed light on the impact of distillation on formation and progression of the thermal front and reaction kinetics associated with the vapor phase oxidation/combustion. For the purpose of this study, oxygen and nitrogen injection experiments were performed on a recombined light oil core sample in a 45cm long, ramped temperature oxidation (RTO) reactor. This paper concentrates on selected tests which highlight the distillation behavior. The presence of an endothermic vaporization front accompanying the exothermic thermal front in the RTO experiments was observed in this research. The nature of the thermal front depends on whether the concentration of hydrocarbon in the vapor phase falls in the flammable range.