Bitumen Recovery Processes Research Articles

Investigation of Unresolved Interface "Rag Layer" in Athabasca Oil Sand Bitumen In Situ Recovery.

Steam-assisted gravity drainage (SAGD), the leading commercial in situ bitumen recovery process, involves the underground injection of steam and produces at the well head a hot fluid containing water, hydrocarbons, and sand. This fluid is subjected to separation by diluent addition and gravity in several parallel treaters. Occasionally, the separation may be disrupted in one or few treaters by the occurrence of an unresolved interface or "rag layer" while continuing without disruption in the rest of the treaters. In the current study, we investigate "rag layer" occurrence based on the quantification of laboratory-scale and SAGD field tests and imaging of the "rag layer" morphology. The quantification results show that the formation and volume of the "rag layer" are affected by solids, mixing speed, and solvent addition. The microscopic images demonstrate the presence of both water-in-oil or oil-in water emulsions with a distinct transition between the continuous phases. The visual detection boundaries of the "rag layer" are defined as the threshold between the agglomerated and individual droplet layers. The extent of agglomeration increases in the proximity to the oil-water interface. The contribution of hydrophobic fine inorganic solids (less than 10 μm) to forming a "rag layer" is supported by their accumulation observed at the treaters' oil-water interface, compared to the feed. In well-controlled field operations, the perceived randomness of "rag layer" occurrence could be associated with the fluctuation of fine solid contents in the feed.

Molecular insights into oil detachment from hydrophobic quartz surfaces in clay-hosted nanopores during steam–surfactant co-injection

Thermal recovery techniques for producing oil sands have substantial environmental impacts. Surfactants can efficiently improve thermal bitumen recovery and reduce the required amount of steam. Such a technique requires solid knowledge about the interaction mechanism between surfactants, bitumen, water, and rock at the nanoscale level. In particular, oil sands ores have extremely complex mineralogy as they contain many clay minerals (montmorillonite, illite, kaolinite). In this study, molecular dynamics simulation is carried out to elucidate the unclear mechanisms of clay minerals contributing to the bitumen recovery under a steam–anionic surfactant co-injection process. We found that the clay content significantly influenced an oil detachment process from hydrophobic quartz surfaces. Results reveal that the presence of montmorillonite, illite, and the siloxane surface of kaolinite in nanopores can enhance the oil detachment process from the hydrophobic surfaces because surfactant molecules have a stronger tendency to interact with bitumen and quartz. Conversely, the gibbsite surfaces of kaolinite curb the oil detachment process. Through interaction energy analysis, the siloxane surfaces of kaolinite result in the most straightforward oil detachment process. In addition, we found that the clay type presented in nanopores affected the wettability of the quartz surfaces. The quartz surfaces associated with the gibbsite surfaces of kaolinite show the strongest hydrophilicity. By comparing previous experimental findings with the results of molecular dynamics (MD) simulations, we observed consistent wetting characteristics. This alignment serves to validate the reliability of the simulation outcomes. The outcome of this paper makes up for the lack of knowledge of a surfactant-assisted bitumen recovery process and provides insights for further in-situ bitumen production engineering designs.

Density and viscosity of multicomponent diluent/bitumen mixtures with application to in-situ bitumen recovery and diluted bitumen transportation

The extraction of bitumen relies on energy-intensive methods, and its transportation necessitates dilution due to its high viscosity. Hence, there is a growing demand to explore alternative approaches that are cost-effective and energy-efficient to enhance the extraction and transportation processes. While there is ample thermophysical data available in the literature regarding the individual performance of pure solvents and bitumen systems, there is a significant gap in data concerning density and viscosity measurements for multicomponent solvents and their interaction with bitumen. This study presents new measurements by investigating the effect of varying multicomponent diluent concentrations (7 to 70 wt%) on the density and viscosity of multicomponent diluent/Mackay River bitumen system in a pressure range of 1.291–8.769 MPa and a temperature range of 295–389 K. These thermophysical data are essential in the design, optimization, and reservoir simulation of solvent-based and solvent-aided recovery processes, as well as the surface processing and transportation of diluted bitumen. The findings demonstrated that the addition of the diluent, even at a lower mole fraction, has a notable impact on reducing both the density and viscosity of the bitumen. As part of this study, we have also obtained empirical correlations based on well-established relationships that can be employed as predictive tools for estimating the density and viscosity of a multicomponent diluent/bitumen system. The obtained correlations estimate the density and viscosity of mixtures of bitumen and diluent with average absolute relative deviations (AARD) of 0.4 % and 16.29 %, respectively. The new experimental data are then used to perform zeroth-order energy, greenhouse gas emission, and carbon tax recovery analyses of solvent-aided viscosity reduction. The results reveal that the utilization of natural gas condensate as a diluent leads to significant energy reductions and greenhouse gas emissions. The results find applications in solvent-based and solvent-aided bitumen recovery processes, surface processing, and the transportation of diluted bitumen.

Gravity Drainage of Bitumen Induced by Solvent Leaching.

Steam-based thermal recovery processes are energy-intensive and pose environmental concerns due to their high greenhouse gas emissions. The application of solvents has shown promise in reducing the environmental impact of these processes. In this work, the solvent chamber theory is used to study the gravity drainage of bitumen. The results reveal that the drainage rate can be scaled using the thermophysical properties of solvents. The drainage rate is shown to be directly related to the density difference between bitumen and solvent and inversely proportional to the mixture viscosity. A universal scaling relation between the Sherwood number, as a measure of the mass transfer, and Rayleigh number, as a measure of the natural convection, in the form of Sh = βRa is presented using the experimental data of various solvents. This linear relationship is consistent with the theoretical studies of buoyancy-driven convection. Moreover, the scaling prefactor β is found to decrease with increasing natural log of the mobility ratio (α), which results in a lower rate of convective mass transfer. Furthermore, a new critical Rayleigh number equation based on the power-law mixing rule (PLMR) is derived, and the results are compared with the available theories in the literature based on the exponential mixing rule (EMR). The findings provide insights into understanding the convective dissolution with large viscosity contrast. Furthermore, the developed scaling relation provides a useful tool to predict the convective mixing of different bitumen/solvent systems. The results find application in the design of the solvent-based bitumen recovery processes.

Measurements and Modeling of the Dissolution and Exsolution Kinetics of the Ethane/n-Heptane System

Solvent-aided thermal recovery processes have been suggested and implemented to reduce the environmental impact of steam-based heavy oil and bitumen production. The injected solvents often undergo dissolution (exsolution) into (from) the oil phase throughout the heavy oil and bitumen recovery processes. New experimental data at elevated pressures and temperatures are essential to better understand the dissolution and dissolution kinetics of various solvents. To eliminate this gap, a new experimental setup was developed to study the kinetics of exsolution and dissolution of gases. The developed setup was used to study the exsolution of ethane from ethane-saturated heptane and the dissolution of ethane in heptane in a temperature range of 60 to 120 °C. An analytical model was adapted to model the experiments and estimate the diffusion coefficients of exsolution and dissolution of the ethane/heptane system. The results indicate that the exsolution of ethane from heptane is much faster compared to its dissolution. The molecular diffusion coefficients for exsolution and dissolution were found to be in the range of (2.02–5.44) × 10–6 and (1.76–11.80) × 10–8 m2/s, respectively. The measured experimental data were modeled using the Arrhenius-type kinetics. The results revealed lower activation energy for the exsolution of ethane from ethane-saturated heptane compared to its dissolution. The reported dissolution and exsolution data sets find applications in the design, simulation, and optimization of solvent-aided thermal recovery of bitumen/heavy oil and various chemical processes.

A semi-compositional approach to model asphaltene precipitation and deposition in solvent-based bitumen recovery processes

Steam assisted gravity drainage (SAGD), as a commercially proven high ultimate recovery process for heavy oil and bitumen is energy intensive and may be limited by high usage of water. In the recent years, numerous methods to combine solvent and heat have been proposed for the in-situ recovery of bitumen. Among these methods, N-Solv (heated solvent vapor injection) and EBRT (enhanced bitumen recovery technology) utilize heated solvent vapor to extract heavy crudes under in situ conditions. These methods take the advantage of partial in situ upgrading of oil with much lower consumptions of water and natural gas and have the potential to reduce greenhouse gas (GHG) emissions. However, with the current knowledge relevant to solvent/heat-assisted recovery processes, it still remained uncertain how the in-situ upgrading could impact ultimate recovery and the efficiency of these processes. This study, thus, aims at providing insights about these processes with a numerical model. The study develops a simulation model that captures important mechanisms involved in the processes such as diffusion/dispersion, solvent dissolution, asphaltene precipitation and potential deposition. The complexity of modelling such processes is due to interrelation of oil–gas phase behavior and fluid transport mechanisms combined with in situ upgrading of oil. The intention is not to only identify factors important to the modeling of these processes, but also find how robust simulation models can be developed to replicate observed field behavior. A semi-compositional approach, based on liquid–liquid equilibrium, is proposed to properly capture the asphaltene precipitation in thermal numerical simulators using direct lab measured data. Our analysis will be presented regarding upgrading mechanisms that should be implemented, their effect on the oil production rate, and techniques to model them.

Mechanism of modification of bitumen zeta potential by sodium citrate: Interactions between bitumen metal content and ligands

Sodium citrate (Na3Cit) has been proved to significantly increase the negative charges on bitumen surfaces, which enhances bitumen liberation and prevents slime coating in the bitumen recovery process. To understand the in-depth theory of Na3Cit modifying the bitumen zeta potential, different assumptions of Na3Cit interacting with bitumen were proposed and experimentally verified in this study. Accordingly, chemicals with similar properties were selected and compared with Na3Cit to confirm the mechanisms. We found that adding Ethylenediaminetetraacetic acid (EDTA) and phosphate (PO43-), which act like citrate as a ligand, resulted in a more negatively charged bitumen surface at pH 8.5 compared with sodium chloride (NaCl). However, even though the sulfate ion (SO42-) carries multiple negative charges, increasing the concentration of sodium sulfate (Na2SO4) led to less negatively charged bitumen surfaces at the same pH, a trend similar to NaCl. Meanwhile, Na3Cit and EDTA promoted the release of metal cations from bitumen to the aqueous solution. However, the concentration of metal ions released by sodium phosphate dibasic (Na2HPO4) was much smaller than expected. Adsorption of Na3Cit, EDTA, and Na2HPO4 on the bitumen surface was observed through mainly outer-sphere complexation and minor inner-sphere complexation. Our study revealed that ligands such as Na3Cit could remove metal ions from bitumen and adsorb onto the bitumen surface, which were the dominant reasons for modifying the zeta potential at the bitumen/water interface.

Dimethyl Ether as a Novel Solvent for Bitumen Recovery: Mechanisms of Improved Mass Transfer and Energy Efficiency

Summary A solvent-based thermal recovery process has the advantages of low capital expenditure, less energy consumption, and less greenhouse gas emission. Dimethyl ether (DME), as a renewable solvent, has been considered as a novel additive in the thermal bitumen recovery process. Being soluble in both water and oil phases, DME has the potential to enhance mass transfer and improve oil production. In this work, a phase behavior model of the DME-bitumen-water system is first developed considering DME partitioning between oil and water. A field-scale numerical simulation model with fine gridblocks is developed to investigate the heat and mass transfer mechanisms between DME and bitumen in the interface of a DME vapor chamber. The numerical model is validated with physical experiment results. The close agreement between measured and simulated production profiles indicates that the mechanisms are adequately captured. Meanwhile, various simulation scenarios are performed to evaluate the production performance and the energy efficiency, which is defined as the energy/oil ratio. It is found that the oil production rate in DME injection is 15% higher than that in butane injection at the early stage of production. The solvent penetration depth in DME injection is larger than that in butane injection. This is attributed to the enhanced mass transfer between DME and bitumen caused by the high diffusion of DME in the water phase and preferential partitioning of DME into the oil phase. Furthermore, energy consumption in the warm DME injection process is 48% less than that in warm butane injection and 75% less than that in steam-assisted gravity drainage (SAGD). This is because DME injection can be operated at a lower-temperature condition, leading to less energy transferred to heat reservoir rock/fluids and less heat loss to over/underburden. Therefore, DME is proved to be a technically promising and environmentally friendly solvent to enhance bitumen recovery. The DME-based thermal recovery technique exhibits superior advantages in unlocking poor-quality reservoirs, especially in high water saturation reservoirs and thin reservoirs.

Incorporating phase behavior constraints in the multi-objective optimization of a warm vaporized solvent injection process

The warm vaporized solvent injection process has been proposed as a more environmentally friendly alternative to steam-based technologies for bitumen recovery. The process typically involves injecting heated solvent vapor into a horizontal injector; the solvent condenses and dissolves into bitumen, while the diluted oleic phase would flow towards a horizontal producer. Despite the promising results reported from several pilot projects near Fort McKay, Alberta, successful commercial-scale extraction is costly and would require a detailed optimization of the pertinent design variables. The main challenge is that this is a multi-objective optimization (MOO) problem, which aims to balance the trade-offs between conflicting performance objectives while honoring the various operational constraints. In this study, a systematic workflow is formulated to optimize these multiple conflicting performance objectives considering phase behavior constraints. A 2D synthetic model based on typical Athabasca oil sands properties is constructed to simulate the warm vaporized solvent process. The addition of non-condensable gas (methane) into the solvent (propane) is examined. The resultant changes in thermodynamic properties and equilibrium phase behavior are considered in determining the practical limits of the decision variables (e.g., bottom-hole injection pressure and temperature). The objective functions, including oil recovery factor, solvent retained-to-oil ratio, and energy consumption, are defined, and a factorial experimental design is employed to identify a subset of decision variables that exhibit minimal redundancy internally and create the dataset for proxy model development. To reduce the computational costs associated with reservoir simulations, proxy models, e.g., the artificial neural network (ANN), is developed and applied. Finally, a Pareto-based MOO scheme is implemented to estimate the optimal decision variables. Despite the higher front-end loading requirement of the ANN proxy modeling, the MOO with proxy modeling still requires significantly less execution/running time as compared to a MOO with traditional flow simulation (e.g., a 97% reduction in CPU time). This reduced running time is important for alleviating the computational load when evaluating the objective functions during the optimization process. More importantly, this optimization scheme is capable of identifying a set of optimal decision variables. This work presents a practical workflow for optimizing various design variables associated with many solvent-based bitumen recovery processes. Specific considerations including the practical limits for operating constraints and computational efficiency are examined and incorporated. It is anticipated that this workflow can be readily integrated into the design and decision-making processes in reservoir management.

The significance of operating parameters on electromagnetic-solvent bitumen recovery process

Current thermal bitumen recovery processes are highly vulnerable to the low oil price environments. Solvents-aided processes could be a promising option over Steam Assisted Gravity Drainage (SAGD), with the potential for lowered initial capital investment and reduced operating costs. Enhanced Solvent Extraction Incorporating Electromagnetic Heating (ESEIEH®) technology is a novel process where electromagnetic waves and hydrocarbon solvents are employed for bitumen recovery.This study examines the significance of operating parameters on the electromagnetic-solvent process when the injected solvent is either pure propane or pure butane. The effect of several parameters, including operating pressure and applied power on various response surface models, were examined using Design of Experiment and multivariate regression analysis. Results show that the operating pressure is the main governing factor for the selection of the solvent type, while other parameters such as applied power are less significant. Generally, it is recommended to operate the process at native reservoir pressure to minimize the risk of loss of expensive solvents into the thief zones.Lack of reservoir containment (leakiness) is another important factor in the process design, especially when prescribing an operating pressure regime considerably different than that of the surrounding impairments. Due to a wide variation of the in-situ bitumen viscosity in different oil sands reservoirs, each bitumen type requires a different solvent mole fraction to mobilize the bitumen. For the type of bitumen used in this study, the optimum pressure range for butane was found to be around 800–1000 kPa, and for propane injection, around 2400–2600 kPa.

Pore-Scale Modelling of Solvent-Based Recovery Processes

A need for a reduction in energy intensity and greenhouse gas emissions of bitumen and heavy oil recovery processes has led to the invention of several methods where mass-transfer-based recovery processes in terms of cold or heated solvent injection are used to reduce bitumen viscosity rather than steam injection. Despite the extensive numerical and experimental investigations, the field results are not always aligned to what is predicted unless several history matches are done. These discrepancies can be explained by investigating the mechanisms involved in mass transfer and corresponding viscosity reduction at the pore level. A two-phase multicomponent pore-scale simulator is developed to be used for realistic porous media simulation. The simulator developed predicts the chamber front velocity and chamber propagation in agreement with 2D experimental data in the literature. The simulator is specifically used for vapor extraction (VAPEX) modelling in a 2D porous medium. It was found that the solvent cannot reach its equilibrium value everywhere in the oleic phase confirming the non-equilibrium phase behavior in VAPEX. The equilibrium assumption is found to be invalid for VAPEX processes even at a small scale. The model developed can be used for further investigation of mass transfer-based processes in porous media.

Measurements and modeling of liquid-liquid equilibrium of Propane + n-Butane + Bitumen system

Propane, butane, and their mixtures (LPG) are considered proper solvents for low temperature upgrading and solvent-based bitumen and heavy oil recovery processes. While equilibrium data for either mixture of propane/bitumen or n-butane/bitumen has been reported in the literature, there is seldom experimental measurement or predictive model for liquid–liquid equilibrium (LLE) of propane + butane/bitumen systems. In this study, comprehensive LLE measurements for propane + n-butane/bitumen mixtures were conducted in a temperature range of 21 to 80 °C and the constant pressure of 3.4 MPa. Equilibrium compositions of propane and n-butane, along with the density and viscosity of the light phase, were measured in each experiment. Then, the heavy yield (wt.%) of the bitumen sample partitioned to the heavy phase was determined. Detailed characterization of light and heavy cuts was performed using combined Simulated Distillation (SD) and Gel Permeation Chromatography (GPC). The bitumen was lumped into two pseudocomponents based on the characterization, and LLE K-values were estimated using a Non-Random Two Liquid (NRTL) model. The tuned NRTL model predicted the experimental compositional data with an AARD of less than 8.5%. The results of this study find application in the design of the solvent-based processes with a multi-component solvent such as liquified petroleum gas (LPG) and set forth an approach for engineering and optimizing the composition of the solvent for these processes.

Condensing Solvent Processes: In Search of the Production Function

Summary The heavy-oil- and bitumen-recovery process by injection of a pure condensing solvent in a solvent vapor chamber provides an alternative to steam-based recovery techniques such as steam-assisted gravity drainage (SAGD). Because of the lower operating temperature between 40 and 80°C, the process uses a much lower energy budget than a steam process and thus results in significantly reduced greenhouse-gas emissions. This paper describes the route to a successful production function with the physical processes at play and using analytical tools. Physical relationships are derived for the solvent/bitumen (S/B) ratio, the bitumen drainage from the roof of the solvent vapor chamber, and for bitumen extraction from both sides of the solvent chamber by the draining condensed solvent. The fast diffusion of bitumen into this narrow liquid solvent zone is likely subtly enhanced by transverse dispersion. The speed of bitumen extraction from the roof of the solvent vapor chamber is constrained by the gas/oil capillary pressure. Extraction from the side of the chamber is approximately three times faster by the action of the thin gravity-draining liquid solvent film. Several equations are provided to enable creation of a heat balance for this condensing solvent process. Laboratory and field observations are matched, including the rates, the heat balance, and the S/B ratio. The model can explain constrained production performance by identifying the rate-limiting steps (e.g., when insufficient solvent condenses). The model predicts high solvent holdup during the rise of the solvent chamber. A method to estimate this solvent liquid saturation is provided. The S/B ratio depends on injector-wellbore heat losses, the (high) liquid saturation in the rising solvent chamber, and the process properties (operating temperature), reservoir properties (heat capacity, porosity, and oil saturation), and solvent properties (density and latent heat). In the existing body of literature, no satisfactory analytical model was available; this new approach helps to constrain production performance and to estimate solvent and heat requirements. The methods in this paper can be used in the future for subsurface project design and performance predictions.

Suitability of hot urea solutions for wettability alteration of bitumen reservoirs – Simulation of laboratory flooding experiments

We report highly fine grid numerical simulation of sandpack flooding experiments conducted using 5 and 10 wt% hot urea solutions for wettability alteration of bitumen reservoirs. Another hot water flooding experiment was also simulated as a baseline for comparison with hot urea solutions. The relative permeability curves have been obtained through history matching of the experimental oil recovery. The results indicated that urea solutions have proved to be efficient in wettability alteration toward more water-wet and attenuation of viscous fingering leading to delayed water breakthrough as was confirmed by the shape of the relative permeability curves. Wettability alteration led to incremental oil recovery compared to the hot water flooding. It was shown that wettability alteration and the in-situ generation of water in oil (W/O) emulsions previously observed in experiments can be captured using the relative permeability curves. These results find application in the design and optimization of thermal bitumen recovery processes.

Numerical modeling of electromagnetic-based thermal recovery techniques combined with solvent injection

Electromagnetic heating (EMH) has been the focus of ever-increasing theoretical and experimental studies to examine if it can be used to heat geomaterials at the field scale. Bitumen recovery process using EMH technique assisted by solvent injection, such as that used in Enhanced Solvent Extraction Incorporating Electromagnetic Heating (ESEIEH®) pilot in currently being conducted in the Athabasca oil sands, utilizes radiofrequency waves to generate a moderate amount of heat in the reservoir. In conjunction with dilution effect of solvent the generated thermal energy reduces the viscosity of highly viscous bitumen leading to its mobilization.Electromagnetic (EM) wave propagation in a reservoir is a coupled multiphysics process that involves not only the heat transfer and fluid flow, but also EM field distribution. Currently, a coupled approach is followed by industry using a commercial reservoir simulator (CMG-STARS) and another commercial software (ANSYS-HFSS) or in-house electromagnetic wave solver with different gridding system where both are linked through a property mapping interface (CEMRS or AxHeat). The coupled scheme utilizes the interface to map parameters from two different gridding structures which causes an additional computational load on the simulation process and could be a source of error. This study presents an alternative integrated compositional numerical modeling approach to explore the EM heating phenomena pertinent to fluid flow and heat generation and transfer in oil sand reservoirs in the same grid structure. Energy balance and EM wave propagation are derived using Maxwell's equations in the frequency domain. Then, the newly developed numerical simulator is validated using benchmark problems and used to demonstrate the physics of EM-induced volumetric heat generation in multi-phase oil sand reservoirs. Finally, the developed numerical model is applied in a case study of propane injection along the antenna to achieve oil recovery and the results are compared with the analogous Steam Assisted Gravity Drainage (SAGD).

2-D physical model experimental study of ethyl acetate and steam co-injection for in-situ bitumen recovery

In this work, we evaluate ethyl acetate (EA) as a solvent for bitumen recovery using a 2-D sand-pack physical model for the first time. EA was considered for co-injection with steam due to the promising results obtained from our recent experimental phase behavior and reservoir simulation studies. Two experiments were conducted by co-injection of 10 and 20 vol% of EA with steam to evaluate expanding solvent steam assisted gravity drainage (ES-SAGD). An experiment was also conducted for the steam assisted gravity drainage (SAGD) as a reference case. The results showed that co-injection of EA increases the bitumen rate. Both ES-SAGD experiments showed a higher production rate compared to SAGD and the superiority of ES-SAGD. The results of 10 and 20 vol% EA co-injection revealed ~65% and ~75% bitumen recovery, respectively, compared to 50% in the case of the SAGD experiment. Co-injection of EA with steam also decreased the cumulative steam-oil-ratio (cSOR), which is desirable in bitumen recovery processes. ES-SAGD experiments reduced the cSOR by 1.5 to 2.5 units, which is 20 to 32% lower than SAGD. This reduction in cSOR results in significant energy savings and lower greenhouse gas emission intensity. The cumulative energy-oil-ratio was also measured, and the results showed that co-injection of EA decreases the energy-oil-ratio by 17–22% compared to SAGD. Moreover, it was observed that implementation of EA significantly reduces the water-oil emulsion stability, which is favorable in oil/water separation and treatments of the produced water.

Concentration Dependence of Mutual Diffusivity of Liquid Hydrocarbons and Bitumen

The mutual diffusivity of solvent and bitumen is an important parameter in the design of solvent-based bitumen recovery processes. It is determined from measured concentration profiles in bitumen. ...

Development of Generalized Correlations for Thermophysical Properties of Light Hydrocarbon Solvents (C1–C5)/Bitumen Systems Using Genetic Programming

Accurate modeling of thermophysical properties of solvent/bitumen mixtures is critical for proper design and implementation of thermal- and solvent-based bitumen recovery processes. In this study, three generalized correlations were developed for prediction of solubility, density, and viscosity of light hydrocarbon/bitumen mixtures. The generalized correlations were developed using symbolic regression based on genetic programming and employing a 10-year set of comprehensive phase behavior experimental studies conducted under the SHARP research program on solvent-aided thermal recovery of bitumen. The data set comprised Surmont, JACOS, Mackay River, and Cold Lake bitumen samples and five light hydrocarbon solvents including methane, ethane, propane, n-butane, and n-pentane. The developed correlations are valid for gaseous solvents. Finally, the developed correlations for solubility, density, and viscosity were validated against a large data set of experimental measurements collected from the literature. The validation demonstrates that the developed correlations are able to accurately predict the available experimental data of solubility, density, and viscosity reported in the literature.

Effect of asphaltene content in bitumen on thermodynamic properties of light hydrocarbons dissolving in bitumen

Solvent recovery from diluted bitumen and froth treatment tailings, produced during the bitumen recovery process for mined oil sands, requires an understanding of the thermodynamic equilibrium and kinetics of solvent dissolution in bitumen. Thermodynamic properties of solvent in bitumen having various asphaltene contents are needed in order to model and improve the solvent recovery process. In this work, the thermodynamic properties of light hydrocarbons in bitumen were investigated using an inverse gas liquid chromatography (IGC) method. Bitumen containing different amounts of asphaltenes (0 wt%, 2.6 wt%, 9.9 wt%, 36.9 wt%, and 53.7 wt%) were used as the stationary phase of the chromatographic column, while light hydrocarbons were injected into mobile phase. The specific retention volumes of the hydrocarbons in bitumen, Vgo, were measured at different temperatures (333.2 K–393.2 K). Thermodynamic properties of these light hydrocarbons in bitumen, including infinite dilution activity coefficient, γ∞, enthalpy of solution, ΔHo, heat capacity changes, ΔCpo, Gibbs energy change, ΔGo, as well as entropy of solution change, ΔSo, were then calculated based on thermodynamic principles and data obtained from IGC measurements.

Effect of additives on liquid–liquid equilibrium properties of butane/bitumen systems with applications to solvent aided bitumen recovery processes

Solvent-aided bitumen recovery processes are relatively new approaches to reduce the negative environmental impacts and production costs of steam assisted gravity drainage (SAGD). Thermo-physical properties of these systems such as density, viscosity, phase partitioning and saturation pressure are of great importance in design of solvent-aided processes. Butane is a promising solvent for solvent-aided bitumen recovery processes. Addition of light or heavier solvents to butane can provide an engineering solution to improve the efficiency of solvent-aided processes. In this study, equilibrium measurements of butane and bitumen mixture were conducted at temperatures of 40 and 60°C and pressures well above vapour pressure of the solvent. Then, the effect of introducing a second solvent as an additive to the butane–bitumen mixture was investigated. Propane, toluene and dimethyl ether were added to the original mixtures of butane and bitumen in separate sets of experiments and changes in thermo-physical properties were determined. It was determined that adding butane can lower the viscosity of the bitumen by several orders of magnitude. It was also concluded that although propane can significantly increase the saturation pressure of the mixture, it results in higher amount of asphaltene precipitation. The effect of dimethyl ether however is favourable because not only increases the vapour pressure but also reduces the asphaltene precipitation similar to toluene.