Bitumen Solvent Research Articles

Smectite-bitumen interactions in non-aqueous bitumen extraction process

The non-aqueous extraction (NAE) is an alternative to the commercial water-based extraction technology used to liberate bitumen from oil sands. Although the impact of kaolinite, illite, chlorite, illite-smectite and montmorillonite on NAE process has been previously studied, the effect of different types of smectites has not been fully understood yet. In this work, mixtures of bitumen with bentonites dominated by saponite, hectorite, nontronite, beidellite and montmorillonite were reacted for several days and then washed with solvent (cyclohexane) to remove bitumen from the bentonites. The main goal was to better understand the impact of different smectites properties (specific surface area, pore structure characteristics, particle size, crystallite thickness, swelling ability, cation exchange capacity, layer charge and crystal-chemistry of smectites) on NAE process. The results showed that the porosity, particle size and swelling ability were the key parameters affecting the solvent-based bitumen recovery under the studied conditions. Samples with larger initial total pore volume and smaller particle size displayed reduced solvent bitumen extractability. The particle size of studied samples was affected primarily by swelling of smectites during the solvent bitumen extraction experiments. Smectites were swelling in water but not in cyclohexane. Swelling of smectite caused splitting of larger clay particles into many smaller particles. As a consequence, the efficiency of solvent bitumen extraction was significantly lower for fine grained samples, consisting of thin delaminated smectite particles, in which the bitumen was distributed among small-sized clay particles.

Light hydrocarbons solvents solubility modeling in bitumen using learning approaches

In this paper, two types of machine learning, namely neuro-fuzzy inference system (ANFIS) and multilayer perceptron (MLP), have been studied to model light hydrocarbons’ solubility solvent in bitumen. The 268 number of experimental data is used in this work from different articles. The input parameters are Temperature (T), pressure (P), and molecular weight (MW) of hydrocarbons. The result shows the high performance of the MLP model with a two layers to predict the experimental values. The estimated values were investigated by statistical parameters such as R 2, MSE, and MARD%. According to, statistical parameters, the values of 0.99, 0.00081, and 0.68 for MLP, and 0.96, 0.0029, and 0.78 for ANFIS indicate the high performance of the MLP model. Comparison between established models and previous work indicates that the developed model can be a suitable technique for solubility modeling

Experimental study of diffusion of vaporized solvent in bitumen at elevated temperatures

The diffusion coefficient of gaseous solvent in bitumen is an essential parameter in numerical modeling of solvent-assisted thermal recovery processes. The reported measurements of solvent diffusion coefficient are relatively scarce, especially at the high temperature. In this study, a new constant-pressure experimental technique for one-dimensional diffusion tests, which accounts for the bitumen swelling and density change, was developed. A novel analytical model was used to interpret the experimental swelling data. The diffusion coefficients of propane, butane, pentane, hexane and heptane, were measured at temperatures varying from 90 °C to 195 °C. It was found that the diffusion coefficient, at similar solvent solubility, increases with the temperature for all solvents. For different solvents at the same temperature and solubility, the diffusion coefficient decreases with increasing molecular weight of the solvent. A modified power-law correlation of diffusion coefficient with bitumen viscosity and solvent-bitumen mixture viscosity was developed based on the experimental results from this study and other reported studies. The correlation can provide a quick estimation of the diffusion coefficient of gaseous solvent into bitumen.

Experimental study of diffusivity of hexane in bitumen‐saturated porous media under high temperature/pressure conditions

AbstractSolvent mass transfer plays a key role in a thermal gravity drainage process involving solvent. The diffusion coefficients of solvent in such a process are not well studied. This article presents the effective diffusion coefficients of solvent in bitumen‐saturated sands under high temperature/pressure conditions measured using a CT scanning technique. Experimental results show that the effective diffusion coefficient of n‐hexane in bitumen‐saturated sands varied with the solvent concentration or with the viscosity of solvent–bitumen mixture (i.e., De ∝ c0.4 or De ∝ μm−0.46). The solvent concentration weighted diffusion coefficient of n‐hexane in the bitumen under the condition 160–170°C/1,900 kPa had an order of magnitude of about 10−5 cm2/s for solvent volume concentration less than 0.2. The penetration distance of n‐hexane in bitumen‐saturated sands depended on the nonlinearity of diffusion and had a value of −2 cm after 1‐day diffusion. The stronger the nonlinearity of diffusion, the shorter the penetration distance.

Estimation of diffusion coefficient of gases in liquids from swelling data – An analytical model for including the effects of advection and density change

The diffusion coefficient of gaseous solvents in bitumen is an essential parameter in the design and evaluation of performance of solvent-assisted thermal recovery methods. Several analytical and numerical models have been developed as forward models for estimation of diffusion coefficient from experimental data based on various assumptions. However, many critical physical mechanisms such as swelling of the bitumen by solvent dissolution, the swelling-induced advective transport, and the mixture density change by solvent diffusion into the bitumen have not been considered in the previous studies. A simple analytical solution accounting for these mechanisms is lacking and the numerical solution with these mechanisms are computationally-intensive and prone to numerical dispersion. In this study, a novel analytical model is developed to determine the molecular diffusion coefficient of gaseous solvents into the bitumen, including all of the above-mentioned physical processes. The required experimental data for this analytical model are the swelling height (gas-liquid interface movement) with time, during the dissolution of a gaseous solvent at constant pressure in a liquid column. The diffusion coefficients predicted by the present model are compared with values reported in previous studies with different solvents and oil samples. The developed model is able to provide a simple and accurate estimation of the diffusion coefficient from the swelling data with the least number of assumptions. This study provides an improved methodology for estimating the diffusion coefficient of soluble gases in bitumen in systems that exhibit appreciable oil swelling and oil density change.

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.

Determination of binary diffusion coefficients between hot liquid solvents and bitumen with X-ray CT

Abstract The Steam Assisted Gravity Drainage (SAGD) process has been used for in-situ thermal bitumen recovery in Canada. Nevertheless, there are several drawbacks that could impair the SAGD performance. One of the main drawbacks of SAGD is nontrivial consumption of energy to generate steam. To curtail the consumption of steam, many SAGD variants have been proposed. For example, Vapor Extraction (VAPEX) was proposed as a solvent-based cold production method and Solvent-Assisted SAGD (SA-SAGD) was proposed as a solvent-assisted hybrid method. In those solvent-based/assisted methods, the dissolution of solvents in bitumen enhances the in-situ oil mobility. The speed of the mixing between solvents and bitumen in solvent-based/assisted recovery processes is dictated by dispersive mass flux which is proportional to the transverse dispersion coefficient. Diffusion coefficient, tortuosity and transverse dispersivity should be quantified to characterize the transverse dispersion coefficient. In this research, the diffusion coefficients of solvents in Athabasca bitumen were determined with X-ray computed tomography (CT). A medical X-ray CT scanner was used to capture the diffusion phenomenon occurring between fresh liquid solvents and bitumen. The experiments were designed to reproduce the in-situ high pressure, high temperature condition (3.5 MPa, 135C) where solvent and bitumen actually interact at the vapor chamber edge in the SA-SAGD process. Using our new °experimental system, we successfully measured molecular diffusion coefficients at the condition of the vapor chamber edge for the first time. In conclusion, the binary diffusion coefficients between solvents and bitumen were successfully measured at the condition where the mixing of solvents and bitumen actually occurs in the SA-SAGD process. The characterized diffusion coefficients will be input parameters for the reservoir simulation and semi-analytical models.

Estimation of Diffusion Coefficients in Liquid Solvent–Bitumen Systems

Solvent-based recovery processes have gained some advantage over thermal recovery processes under specific reservoir conditions. Solvent–bitumen mass transfer is a diffusion dominated process. The calculation of diffusion coefficients is fundamental for the design of solvent-based recovery processes as it allows us to understand the performance of the process. In a recent work, Babak et al.(1) developed a new slopes and intercept method which was demonstrated to be very robust for the calculation of diffusion coefficients of binary systems. In this paper, the diffusion coefficients of dimethyl ether (DME), pentane, and toluene into two different bitumen systems are calculated using this method as a function of concentration. X-ray computed tomography (CT) is used to obtain the concentration profiles of the bitumen–solvent systems. Furthermore, a new modification of Vignes’ equation is introduced to predict concentration-dependent diffusion coefficients. This new modification includes the acceleration and ...

New Solubility and Viscosity Measurements for Methane–, Ethane–, Propane–, and Butane–Athabasca Bitumen Systems at High Temperatures up to 260 °C

One of the important mechanisms in solvent-aided thermal recovery processes is viscosity reduction due to dissolution of solvent in the bitumen. This dissolution occurs either with the condensed solvent at the edge of the steam chamber or with direct contact of gaseous solvent and bitumen. Therefore, it is essential to determine the solubility and viscosity of solvent in bitumen for reservoir simulation of solvent-aided thermal recovery processes. We report new experimental viscosity and solubility data of methane–, ethane–, propane–, and butane–Athabasca bitumen systems at high temperatures (up to 260 °C). The experimental measurements have been conducted under liquid–vapor equilibrium conditions. Peng–Robinson Equation of State (PR-EoS) was employed to model the solubility data. The tuned PR-EoS represented the experimental solubility data of methane, ethane, propane, and n-butane in bitumen with absolute average relative deviations of 5.7, 4.1, 7.8, and 4.9%, respectively. The reported data find applic...

A new analytical model for estimation of the molecular diffusion coefficient of gaseous solvents in bitumen – Effect of swelling

Diffusion of gaseous solvents in bitumen is one of the imperative factors in studying solvent-aided thermal recovery processes. Experiments have shown significant swelling of bitumen upon diffusion of some gaseous solvents. Among different techniques for measurement of diffusion coefficient, Pressure Decay methods are the most popular. In one approach, liquid is placed in a cell overlaid by a gas cap. Diffusion of gas into the liquid at constant cell pressure can be achieved by continuously supplying the makeup gas into the gas cap. Different analytical and numerical models to estimate the molecular diffusion based on the mass of the injected gas have been proposed in the literature. However, there are two drawbacks associated with the previous models: 1) most of these models have been developed based on a no-swelling assumption while experiments have shown the significant swelling of bitumen upon diffusion of some solvents; 2) the models that incorporate the effect of swelling are numerical or semi-analytical and they are computationally-expensive, not straightforward, and prone to numerical error. Therefore, there is need for a simple analytical model that not only includes the swelling effect, but also is easy to implement. This study presents a novel analytical model obtained based on similarity solution along with a simple graphical method to estimate diffusion coefficients of gases in liquids. The experimental data of a moving interface as a result of swelling is used as an input to the developed model to estimate the diffusion coefficient. The developed model is applied to the available data in the literature and the predicted diffusion coefficients are compared to the previously reported ones. Moreover, the presented model is used to interpret new experimental data of nC4-nC10 system to estimate the molecular diffusion coefficient. The developed model and the experimental data find applications in design and optimization of solvent-aided thermal recovery of bitumen and heavy oils.

Asphaltene Deposition during Bitumen Extraction with Natural Gas Condensate and Naphtha

Solvent bitumen extraction processes are alternatives to thermal processes with potential for improved economic and environmental performance. However, solvent interaction with bitumen commonly results in in situ asphaltene precipitation and deposition, which can hinder flow and reduce the process efficiency. Successful implementation requires one to select a solvent that improves recovery with minimal flow assurance problems. The majority of candidate industrial solvents are in the form of mixtures containing a wide range of hydrocarbon fractions, further complicating the selection process. In this study, we quantify the pore-scale asphaltene deposition using two commonly available solvent mixtures, natural gas condensate and naphtha, using a microfluidic platform. The results are also compared with those of two typical pure solvents, n-pentane and n-heptane, with all cases evaluated with both 50 and 100 μm pore-throat spacing. The condensate produced more asphaltenes and pore-space damage than the napht...

Mineralogy and Surface Chemistry of Alberta Oil Sands: Relevance to Nonaqueous Solvent Bitumen Extraction

The mineralogy, chemistry, surface properties, and pore structure characteristics of the four different petrologic types of Alberta oil sands were determined in order to better understand their impact on nonaqueous solvent bitumen extraction. Quartz, clay minerals, and carbonates were the main mineral constituents of the studied samples. With increasing weight percentage of clay minerals, the solvent bitumen extraction (by the Dean–Stark procedure using toluene) decreased. Fine grained illite and illite-smectite had more detrimental effect on solvent bitumen extraction than coarse grained kaolinite. The pore structure data revealed that the extractability of bitumen from the oil sands depends on accessibility, more specifically on the size of bitumen-filled pores, by the solvent. The relative abundance and size of pores in the oil sands were controlled by mineral composition and particle size. Fine size fractions were typically enriched in kaolinite and 2:1 clay minerals (illite and illite-smectite) and c...

Can a Cubic Equation of State Model Bitumen–Solvent Phase Behavior?

Cubic equations of state (CEoS), such as the advanced Peng–Robinson (APR) EoS, are convenient for use in commercial simulators and have successfully fit saturation pressures and asphaltene onset points for bitumen–solvent systems using simple quadratic mixing rules. However, this approach does not accurately predict asphaltene precipitation yields. In this study, the APR EoS with several sets of asymmetric mixing rules is evaluated against saturation pressure and asphaltene yield data for n-pentane diluted bitumen. The asymmetric van der Waals, Sandoval et al., and two forms of Huron–Vidal mixing rules with an NRTL (non-random liquid theory) activity coefficient model are considered. The use of asymmetric mixing rules significantly improves the match to asphaltene yield data; however, the yields are still underpredicted at high solvent contents, and the tuning parameters that give the best match for asphaltene yield data are not predictive or easily correlated for other solvents. The APR EoS with symmetri...

Experimental and modeling studies of water, light n-alkanes and MacKay River bitumen ternary systems

Water plays an important role as energy carrier in the solvent-aided thermal recovery processes of heavy oil and bitumen. The effect of water on phase behaviour of bitumen and solvent (light n-alkanes) mixtures is often ignored in thermal reservoir simulation. In this work, the effect of the presence of water on the phase behaviour of solvent in bitumen is studied. The solubility of solvents in bitumen as well as the density and viscosity of the bitumen rich phase are measured in both the presence and the absence of water. Results show a remarkable effect of water on solvent solubility in bitumen especially at high temperature conditions (T>150°C). A three-phase equilibrium calculation of the water-solvent-bitumen ternary system is carried out using a Peng-Robinson equation of state (PR-EoS) coupled with Henry’s constant. The results show that the PR-EoS regenerates the ternary system with acceptable accuracy. The density and viscosity of the bitumen rich phase in the presence of water are correlated using the experimental binary data.

Pore-scale analysis of condensing solvent bitumen extraction

Current thermal methods for bitumen recovery are effective but require both environmental and economic performance improvements. Light hydrocarbon solvent injection is an alternative to steam injection that has the potential to reduce greenhouse gas emissions associated with recovery. However, the pore-scale behavior of the solvent-bitumen system is very complex and poorly characterized to date. In this work, a high-pressure high-temperature micromodel with reservoir-relevant geometry combined with imaging tools provides a pore-scale window into solvent injection methods using propane and butane. The combination of two-phase dynamics and solvency at the condensing edge leads to significant bitumen production, similar in both propane and butane injections. In the liquid zone ahead of the condensing edge, butane results in dense, small, and immobile solvent-in-residue emulsions. In contrast, liquid propane produced larger emulsions with some mobility. Spectroscopy combined with fluorescence imaging indicated that the residual immobile emulsions in the butane case are bitumen heavy fractions, and largely asphaltenes. Collectively this work highlights the distinct recovery mechanisms and limitations at both the condensing front and liquid zone for these common solvents.

Effect of Swelling Clay Minerals (Montmorillonite and Illite-Smectite) on Nonaqueous Bitumen Extraction from Alberta Oil Sands

Two natural clay standards, dominated by montmorillonite (SWy-2) and Illite-smectite (ISCz-1), were mixed with bitumen and reacted for 8 days. The clay-bitumen mixtures were then washed three times each with cyclohexane to extract bitumen from the clays. The aim was to better understand the role of swelling clay minerals on nonaqueous solvent bitumen extraction. The experimental results showed that montmorillonite and Illite-smectite contained 4.6 to 8.2 wt % and 7.1 to 8.2 wt % of carbon after cyclohexane bitumen extraction, respectively. The residual organic material after cyclohexane bitumen extraction was retained on the outer and inner (interlayer space) surfaces of the swelling clay mineral particles in the form of patchy rather than continuous coating. Cation exchange capacity (CEC), specific surface area (SSA), and layer charge density (LCD) were all reduced by the reaction with bitumen due to organic coatings on the clay mineral surfaces and/or due to gluing of clay particles to aggregates. Compa...

Numerical simulations of bitumen recovery using solvent and water assisted electrical heating

Application of solvent and water assisted electrical heating for in-situ extraction of bitumen is demonstrated. In this process heat is provided to the formation using downhole electrical heaters with injection of a working fluid to enhance the heat transfer. As a result, a hot vapor chamber analogous to that created in the steam assisted gravity drainage (SAGD) is formed. In this study results of numerical simulations using water, pure solvents, and combined water and solvents as working fluids are presented. The solvents considered are butane, hexane, and natural gas condensate. It was shown that while pure solvent injection is not as effective as water in transferring heat, co-injection of hexane or condensate with water is able to accelerate production as a result of the dilution effect of solvent in bitumen along with effective convective heat transfer. The results show promise and demonstrate that this process has potential to entirely eliminate steam generation plant and significantly reduce the size of the required water treatment surface facilities. Many potential advantages of solvent and water assisted electrical heating over SAGD result from the capital and operational cost perspectives.

Estimation of Low-Temperature Mass-Transfer Properties of Methane and Carbon Dioxide in n-Decane, Hexadecane, and Bitumen Using the Pressure-Decay Technique

The pressure-decay technique is used to determine the diffusivity and solubility of methane and carbon dioxide in pure hydrocarbons and bitumen at temperatures of 0, 15, 20, and 25 °C and pressure of 3.5 MPa. An analytical–graphical technique is implemented to extract the related mass-transfer parameters, i.e., diffusion coefficient and Henry’s constant, from the pressure-decay data. The results reveal that the diffusion coefficient of methane and carbon dioxide in both pure hydrocarbons and bitumen decreases as the temperature decreases. On the basis of the estimated Henry’s constants, the effect of the temperature on the solubility of the gaseous solvents in bitumen and pure hydrocarbons is also determined. As expected, the solubility of both gases in the studied pure hydrocarbons increases as the temperature decreases. In addition to confirmation of the known trends, this study provides new experimental data for the low-temperature gas–hydrocarbon diffusion process.

Cracking Mechanism and Repair Techniques of Epoxy Asphalt on Steel Bridge Deck Pavement

Epoxy asphalt concrete is widely used for long-span steel bridge deck pavement in China. Because of the heavy traffic load and extreme climatic conditions, epoxy asphalt deck pavement tends to develop cracks, debonding, and potholes and needs reconstructing typically after 5 to 10 years. Research was performed on the cracking mechanism under both traffic and thermal loads, with the aim of finding the best sealing material. The performances of various crack-sealing materials, including workability, mechanical property, and durability, were evaluated. Test methods such as the simplified penetration ability test and bending fatigue test were employed for rating the crack-sealing materials. Experimental results revealed that the traditional crack-sealing materials, such as bitumen modified with styrene–butadiene–styrene, rubber bitumen, bitumen emulsion, and solvent bitumen, cannot meet the requirements for repairing epoxy asphalt on long-span bridge decks because of the low penetration ability and low adhesive strength. Results showed that cracks could be repaired well with epoxy resin–sealing materials, which showed great penetration ability, high bond strength, large deformation capacity, and short curing time.

Influence of Nonswelling Clay Minerals (Illite, Kaolinite, and Chlorite) on Nonaqueous Solvent Extraction of Bitumen

Artificial mixtures of bitumen with three natural clay standards, dominated by illite, kaolinite, and chlorite, were reacted for several days and washed three times each with cyclohexane to remove bitumen from the clays. The main goal was to determine and better understand the effect of nonswelling clay minerals (illite, kaolinite, and chlorite) on nonaqueous solvent bitumen extraction. The experimental results showed that the total amount of residual cyclohexane insoluble organic carbon (CIOC) measured for clay–bitumen mixtures after nonaqueous solvent bitumen removal is a function of intrinsic resistance of high molecular weight (MW) organic compounds to cyclohexane extraction and the nature of nonswelling clays. The intrinsic resistance of high MW organic compounds to cyclohexane extraction accounted for 42–80% of the total CIOC content. The nonswelling clays retained from 20 to 58% of CIOC of the total CIOC content primarily on the external surfaces (basal planes and edges) of clay mineral particles i...