•A detailed critical review of electromagnetic heating was provided.•Most of the simulation and laboratory studies showed that the process is economically feasible.•A limited number of field ...applications showing the efficiency of the method were evaluated.•Microwave receptors (carbon, nano-metal oxides, and polar solvents) should be used for faster process.•Further research is needed to implement the use of metal-nanoparticles in this process.
Thermal methods are inevitable in heavy oil/bitumen recovery. Different types of “aqueous” methods such as cyclic steam and hot water injection, in-situ combustion, hot water and steam flooding, and steam assisted gravity drainage have been widely applied over decades. Currently, non-aqueous heating methods, generally named electromagnetic, are in consideration as an alternative to the aqueous methods, which may not be applicable due to technical and environmental limitations. This technique still requires further research and field scale pilot applications to prove their technical and economic viability.
In this paper, a critical discussion on the review of electromagnetic heating is presented. An attempt is undertaken to review most of the research works (computational and experimental as well as a limited number of field applications) performed over more than five decades. After evaluating aqueous and non-aqueous thermal methods, a comparative analysis is presented.
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The objective of this work is to clarify the mechanisms of additional viscosity reduction of heavy oil/bitumen using nano-size metal particles during steam injection techniques. For this purpose, ...three sets of experiments are designed. The objective of the first series of experiments was to study the effect of metal particles on the viscosity of the produced oil at low temperature. Viscometry experiments at temperatures below 100°C were conducted for this purpose. Then, their effect was studied in the presence of aqueous phase at high temperature of 300°C to simulate the steam stimulation processes. The third set of experiments was designed to study the effect of micro- and nano-sized metal particles on the enhancement of heat transfer within the oil phase.
The experiments showed that at low temperatures, the particles reduce the heavy oil viscosity after being mixed with the oil phase. The amount of the viscosity reduction is a function of the concentration of the particles and there exists an optimum concentration of particles yielding maximum amount of viscosity reduction. Also, the trend of viscosity versus concentration of the particles is a function of the type and size of the metal, and the temperature. The second series of experiments revealed that the same trend of viscosity versus concentration of particles is observed at steam injection conditions. However, much higher degree of reduction in viscosity was observed in this case compared to the low temperature experiments. The third series of experiments showed that metal particles used at their optimum concentration do not provide significant improvement of heat transfer.
The experiments provided a good understanding of the ongoing mechanisms that would lead to a viscosity reduction by the addition of metal particles. The concentration, type, and size of the particles were found to be highly critical on viscosity reduction. The optimal values of these parameters were identified. The results and observations are expected to be useful in further studies and applications as to the efficiency improvement of the thermal applications for heavy-oil/bitumen recovery.
•The mechanism behind the viscosity reduction caused by metal particles is explained.•Nano-sized particles have a remarkable effect on heat transfer through heavy oil compared to micron size.•Different metal types (iron, nickel and copper) of different sizes were tested and compared first time.•There exists a minimum for all cases indicating an optimal value of concentration.•The effect of particle size (nano versus micro) on the viscosity reduction process was specified quantitatively.
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The thermodynamics of fluids in confined (capillary) media is different from the bulk conditions due to the effects of the surface tension, wettability, and pore radius as described by the classical ...Kelvin equation. This study provides experimental data showing the deviation of propane vapour pressures in capillary media from the bulk conditions. Comparisons were also made with the vapour pressures calculated by the Peng-Robinson equation-of-state (PR-EOS). While the propane vapour pressures measured using synthetic capillary medium models (Hele-Shaw cells and microfluidic chips) were comparable with those measured at bulk conditions, the measured vapour pressures in the rock samples (sandstone, limestone, tight sandstone, and shale) were 15% (on average) less than those modelled by PR-EOS.
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Phase-alteration phenomenon has a considerable influence on the dynamics and distribution of fluids in porous media. One of the major factors affecting the phase behaviour of fluids in reservoirs is ...the capillarity effect, which becomes unavoidably significant as the media becomes tighter (confinement effect) and contains more pores at nano sizes. Comprehending the nature of vaporization and condensation of hydrocarbon in such confined media is important for accurate modelling of two-phase envelopes and thereby the performance of energy production from hydrocarbon reservoirs. This paper studies the vaporization of single- and multicomponent hydrocarbons in different types of rocks (namely sandstones, limestones, tight sandstones, and shales). The vaporization temperatures were measured experimentally in each rock type and compared with boiling points measured at bulk conditions to investigate the deviation between the phase-change temperatures in capillary media and bulk values. The deviation between the measured vaporization temperatures and the bulk measurements ranged from 4.4% (1.6% in Kelvin unit) to 19.7% (5.2% in Kelvin unit) with single-component solvents and 1.4% (0.4% in Kelvin unit) to 27.6% (5.3% in Kelvin unit) with the hydrocarbon mixtures. The vaporization temperatures, obtained from the experiments, were also compared with the computed two-phase envelopes, calculated by the classical Peng-Robinson Equation of State. The deviation percentages of measured vaporization temperatures from the computed values were at least 4.4% (1.6% in Kelvin unit) with single-component solvents and 2.1% (0.7% in Kelvin unit) with the hydrocarbon mixtures.
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This paper presents qualitative and quantitative analysis of single and multiphase flow in a single fracture based on experimental results and demonstrates relationships between the roughness and ...fluid movement and distribution. Experiments were conducted on seven perfectly-matching and tightly-closed rough model fractures reproduced from the single fractures of lithologically different seven rock blocks that were jointed artificially through laboratory indirect tensile tests. Transparent upper and opaque lower walls of these models facilitated the visualization of the flow experiments. Rough surfaces of the model fractures were first digitized. Then, using the gathered data in variogram analysis, surface roughness was quantified by fractal dimension. Another roughness quantification parameter was also handled as the ratio between total fracture surface area and planar surface area. Experimental measurements of flow were quantitatively correlated to surface roughness under different normal loading (aperture) conditions. Also, constant rate immiscible displacement experiments were performed to assess the roughness effect represented by seven different lithologies and wettability effect controlled by the material used in manufacturing the fracture samples on the residual saturation development.
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•GBM can reproduce strength and elastic properties of granites.•Properties of multiple granites could not be matched simultaneously.•Crack development strongly depends on mineral and particle ...distribution.•Heterogeneity of rocks and rock masses is properly represented by DEM.
The influence of mineral size and distribution, and model discretization on elastic rock properties, rock strength, and types and numbers of micro cracks was studied numerically using a two-dimensional discrete element grain based modeling (GBM) approach. The model was calibrated to unconfined and confined compression tests and Brazilian tensile tests performed on Aue granite. Confined asymmetric compression tests were simulated for the same rock and compared to physical fracture paths. The GBM approach is able to reproduce all major laboratory observations including the correct ratio between compression strength and Brazilian tensile strength that cannot be captured with earlier contact models.
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Tight sands are abundant in nanopores leading to a high capillary pressure and normally a low fluid injectivity. As such, spontaneous imbibition might be an effective mechanism for improving oil ...recovery from tight sands after fracturing. The chemical agents added to the injected water can alter the interfacial properties, which could help further enhance the oil recovery by spontaneous imbibition. This study explores the possibility of using novel chemicals to enhance oil recovery from tight sands via spontaneous imbibition. We experimentally examine the effects of more than ten different chemical agents on spontaneous imbibition, including a cationic surfactant (C12TAB), two anionic surfactants (O242 and O342), an ionic liquid (BMMIM BF4), a high pH solution (NaBO
2
), and a series of house-made deep eutectic solvents (DES3–7, 9, 11, and 14). The interfacial tensions (IFT) between oil phase and some chemical solutions are also determined. Experimental results indicate that both the ionic liquid and cationic surfactant used in this study are detrimental to spontaneous imbibition and decrease the oil recovery from tight sands, even though cationic surfactant significantly decreases the oil–water IFT while ionic liquid does not. The high pH NaBO
2
solution does not demonstrate significant effect on oil recovery improvement and IFT reduction. The anionic surfactants (O242 and O342) are effective in enhancing oil recovery from tight sands through oil–water IFT reduction and emulsification effects. The DESs drive the rock surface to be more water-wet, and a specific formulation (DES9) leads to much improvement on oil recovery under counter-current imbibition condition. This preliminary study would provide some knowledge about how to optimize the selection of chemicals for improving oil recovery from tight reservoirs.
The concepts of percolation theory and fractal geometry are combined to define the connectivity characteristics of 2-D fracture networks and a new approach to estimate the equivalent fracture network ...permeability (EFNP) is introduced. In this exercise, the fractal dimensions of different fracture network features (intersection points, fracture lines, connectivity index, and also fractal dimensions of scanning lines in X- and Y-directions), and the dimensionless percolation density of fracture networks are required. The method is based on the proposed correlations between the EFNP and a percolation term, (ρ′–ρ′c). The first parameter in this term is the dimensionless density, and the second one is the percolation threshold (a constant number). This term is obtained using the relationships with the properties of fracture networks mentioned above. It was found that the highest correlation coefficient between the actual and the predicted EFNP could be obtained using the percolation term, (ρ′–ρ′c), calculated from the fractal dimension of fracture lines by the box-counting technique. The method introduced is validated using different fracture patterns representing a wide range of fracture and length values. In addition, a correlation between the number of fractures in the domain and the minimum size of the fracture length is presented to estimate the shortest or minimum fracture length required for percolation for a given number of fractures in the domain.
► Correlations to estimate fracture network permeability using 2-D fractal and percolation properties. ► Box-counting dimension is more accurate in the estimation compared to the fractal dimension of other properties. ► Validation exercise confirmed the use of new correlations practically. ► A correlation to quickly estimate the possibility of connectivity (percolation).
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Changing the wetting state of materials is a growing field of research in many areas of engineering and science. In the oil industry, the term wettability alteration usually refers to the process of ...making the reservoir rock more water-wet. This is of particular importance in naturally hydrophobic carbonates, fractured formations, and heavy-oil systems. This shift in wettability enhances oil recovery in oil-wet and weakly water-wet reservoirs and eventually increases the ultimate oil recovery.
For wettability alteration, two methods have been traditionally used: Thermal and chemical. Although many attempts have been made on reviewing the advancement of research in certain aspects of wettability, a comprehensive review of these techniques, especially in terms of the classification of the chemicals used, has been ignored. In this paper, we begin with this review and provide the past experience of wettability alteration in sandstone and carbonate reservoirs. More than 100 papers were reviewed extensively with an in-depth analysis of different methods suggested in literature. The areas of controversy and contradicted observations are discussed. The limitations and the applicability of each method were analyzed. Concerns on up-scaling laboratory findings to field scale are also addressed. The most promising potential methods are identified and their critical conditions highlighted.
At the end, a selection of reviewed methods is validated experimentally for one of the most challenging cases: Extra heavy-oil and bitumen recovery from fractured-strongly-oil-wet carbonates. Berea sandstone (aged to be oil-wet) and Indiana limestone samples were saturated with heavy oil (3600cp). Next, the process was initiated by soaking the cores into solvent (heptane or diluent oil) and the oil recovery was estimated using refractive index measurements. Note that solvent was selected to dilute the oil and recover a considerable amount of oil as any chemical or thermal methods yielded inefficiently low recoveries. After the solvent phase, the samples were exposed to wettability alteration through selected chemicals at different temperature conditions through spontaneous imbibition tests to recover more oil and retrieve the solvent diffuse into the sample back. The most promising wettability alteration agents for each type of rock were marked and optimal application conditions (temperatures, injection sequence) were identified. Selected wettability alteration chemicals were finally tested on the bitumen (5–9° API-1,600,000cp) containing Grosmont carbonate sample from Alberta, Canada.
It is hoped that this review fills in the gap in the area of wettability alteration processes by summarizing, critically analyzing, and testing the methods suggested in the literature.
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•An extensive and critical review of wettability alteration is provided.•Best wettability modifiers for sandstone and limestone were selected.•To apply wettability alteration in heavy oil reservoirs, oil properties has to be changed.•Solvent injection followed by wettability modifiers injection is efficient in heavy-oil /oil-wet systems.•Ionic liquid may provide potential opportunity to be used as wettability modifiers.
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•Globalized approach towards heavy oil emulsions from colloid science to industry.•Prevalence of bitumen emulsions; their shared mechanism and antithetical roles.•Complexity of heavy oil emulsions ...lies in oversimplification of heavy oil types.•“Intelligent” chemical application as a solution to the heavy oil emulsion paradox.
Heavy oil, commonly defined by high density, viscosity, and heavy components distinguishing it from light oil, has a peculiar nature with respect to emulsification. In this article, we delve into the colloid and interface aspects of heavy oil emulsions and their types (heavy oil-in-water emulsion and water in-heavy oil emulsion) along with their industrial applications and occurrences. We observe the paradoxical roles heavy oil emulsions play at different stages of heavy oil production such as upstream, midstream, downstream (and other related areas). First, indigenous surface-active agents in the heavy oil are discussed along with the upstream efforts to generate chemically stable in-situ oil-in-water emulsion in the reservoir to improve displacement efficiency of heavy oil. Functions of naturally formed heavy oil emulsions encountered at the different stages of thermal recovery applications are also presented. This is followed by the review of mid-stream demulsification and emulsification efforts during the oil processing and production periods. The paper is then finalized with the discussion on the final demulsification attempts in the downstream sector defined by the refining process and wastewater management—along with other relevant areas of oil spill and aquifer remediation. With this comprehensive overview of the roles that heavy oil emulsions play in the heavy oil industry, we hope to interconnect the separate, detached views of heavy oil emulsions existing in distinct heavy oil industry sectors and provide a globalized, big-picture view for enhanced understanding of heavy oil emulsions and their applications. The results from this investigation demonstrate that a comparative approach towards heavy oil emulsions is necessary to bolster a more optimal and dynamic manipulation of functions and properties of heavy oil emulsion throughout the industry.
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