Emulsion Flow Research Articles

Crude oil characterization with a new dynamic emulsion stability technique

Crude oils due to its profuse chemical composition produce complex dispersion and emulsion flow behavior with water. The interfacial properties and surface chemistry of oil and water influence heavily the stability, flow behavior and separation of oil and water. In order to understand the crude oil/water emulsion stability better, a new technique is proposed that involves the combined use of a stirred tank cell with interfacial tension and analytical chemistry measurement. Droplet stability parameters like droplet size equilibrium and relaxation time scales have been evaluated and corroborated with surface chemistry of the crude oils. A deeper understanding on how surface-active component like asphaltenes, naphthenic acids and waxes proportion present in crude oils influence emulsion droplet stability is discussed. The 3 crude oils Gjøa, Grane and Bragge were characterized for asphaltenes, naphthanic acids and waxes which was further corroborated with their respective emulsion droplet behavior.

Microscopic visualization of greenhouse-gases induced foamy emulsions in recovering unconventional petroleum fluids with viscosity additives

Greenhouse gas mitigation and utilization attract huge attentions in energy and environment domains worldwide while few technologies enable to satisfy the both concurrently. In this study, a new greenhouse gas utilization technology, foamy emulsions, is initially developed and evaluated. Foamy emulsions usually have low production gas–liquid ratio but capable to facilitate the energy recovery. However, little researches have focused on the formation mechanism and flow property of foamy emulsions under greenhouse gas injection and the use of additives, which results in the relevant mechanism remains unclear. To address this problem, the formation process of foamy emulsions and the influence of the gas type, temperature and amount of viscosity reducer on the flow of foamy emulsions in the process of unconventional fossil fluids are investigated through a series of microscopic visualization experiments. According to the experimental results, the process of foamy emulsions formation can be divided into four stages, namely, the initial, early, middle and late stages. The middle stage corresponds to the period of steady flow of the foamy oil, with the largest number of bubbles and highest velocity. Moreover, the foamy emulsions formed using CO2 as the dissolved gas is the most effective, corresponding to an energy recovery factor of 40%. The effect of N2 is the most inferior, with the corresponding oil recovery factor being only 18%. Although the velocity of the bubbles increases with the increase in the temperature and amount of viscosity reducer, the stability of the bubbles degrades. The optimal effect of the foamy emulsions occurs at 80 °C with the amount of viscosity reducer being 1–3 wt%. This study will support the foundation of more general application pertaining to greenhouse gases mitigation and utilization in energy and environmental practices.

Numerical Study of the Performance Loss of A Centrifugal Pump Carrying Emulsion

The performance and hydrodynamic behavior of centrifugal pumps when handling two-phase liquid-liquid flow and emulsion remain relatively unexplored, although they are of fundamental importance in optimizing the operating conditions of these pumps. Hence, this study aims at investigating the performance degradation of a centrifugal pump under emulsion flow by combined means of analytical and computational fluid dynamic (CFD) models. The analytical approach is based on internal energy loss equations while the CFD approach models the emulsion as a continuous and homogeneous single-phase fluid exhibiting shear thinning behavior. The results give a good insight into the performance degradation of such a system, especially at the best efficiency point (BEP).

Selection of the optimum device parameters for constant magnetic field generation

The aim of the work is to develop a device design for creating constant magnetic fields and select its parameters, select an electrical circuit for powering the device and determine how the energy efficiency of the device changes with an increase in its overall dimensions. When solving the problem, the KOMPAS-3D three-dimensional modeling system was used, the magnetic field induction was calculated using the Pascal ABC programming system, the optimal device parameters were selected using the Microsoft Excel program. Calculations have shown that the coefficient taking into account the inhomogeneous distribution of the magnetic field in the device is 0.883. The optimum ratio between the height and the radius of the cylinder, along which the emulsion flows, is h = r √ 20 hr. Using the KOMPAS-3D three-dimensional modeling system, a model of the device under development was built taking into account the obtained relationships. When using a circuit with an uncontrolled rectifier and autotransformer, the power consumed by the device is 2.67 times lower than the power consumed by the device when using a circuit with a controlled rectifier and a transformer. Energy efficiency increases significantly with the increase in device performance.

Advances of numerical simulation research on the emulsion flow field of wet skin-pass mill

Anti-rust agents are used as emulsion liquids to spray the roll gaps for wet skin-pass of cold-rolled steel strips. The wet-skin strip steel has a good shape, fewer surface defects, good anti-rust effect, higher strength, low roller consumption, and high work efficiency. Some research advances on the numerical simulation of the emulsion flow field in the wet skin-pass mill are discussed, including simplified two-dimensional nozzle models such as straight or convergent, high-pressure jets and conical converging nozzles to provide a theoretical reference for the numerical simulation of the emulsion flow field in the wet skin-pass mill.

Laboratory Evaluation of Fluidity of Heavy Oil Emulsions in Formation Pores Medium.

Heavy oil emulsions such as water in oil (W/O), oil in water (O/W), and water in oil in water (W/O/W) would be formed during the development of heavy oil reservoirs. The key to the efficient development of heavy oil reservoirs is to clarify the fluidity of heavy oil emulsions in formation pores medium. In this study, the main factors that determine the fluidity of heavy oil emulsion were analyzed under the condition of simulating the formation pores medium. The reasons for the difference between the viscosity of heavy oil emulsions in formation pores medium and the viscosity measured by laboratory rheometer were analyzed. Then, experiments have confirmed the shortcomings of the current screening and evaluation method of emulsified viscosity reducer. Finally, through experimental research and mechanism analysis, the mechanism of the emulsified viscosity reducer was studied and suggestions were made to improve the effect of emulsified viscosity reducer in the oil field. When heavy emulsions flow in a formation pores medium, since the size of the droplets would be larger than the size of the pores medium, when the heavy emulsion passes through the pores medium, it would receive additional resistance brought by the Jiamin effect. But when a rheometer is used for viscosity testing, this additional resistance is almost nonexistent. Therefore, the current method of viscosity test using rheometer cannot fully reflect the actual flow state of heavy oil emulsion in formation pores medium. The research in this paper proves that the larger the droplets of the emulsion, the less accurate the rheometer test results. Temperature, permeability, oil–water ratio, and the type of emulsified viscosity reducer all have a certain effect on the flow of heavy oil emulsion in formation pores medium. This article evaluated four types of emulsified viscosity reducers. When the viscosity test was performed by a rheometer, the results showed excellent viscosity-reducing effects. However, when simulating formation pores medium conditions, the effects of some types of emulsified viscosity reducers are not so good. It is no longer accurate to judge the effect of emulsified viscosity reducer by the way of measuring viscosity with a rheometer. It should be screened by the flow capacity of the heavy oil emulsions in formation pores medium. In oil field development, the contact area of heavy oil and emulsified viscosity reducer solution should be increased as much as possible and provide more time for the substitution effect of emulsified viscosity reducer molecules.

Study of the Comprehensive Kinetic Model of Natural Gas Hydrate Formation in a Water-in-Oil Emulsion Flow System.

Hydrate growth is influenced by many factors, including thermodynamics, kinetics, mass and heat transfer, and so on. There is thus a practical significance in establishing a model that comprehensively considers these influencing factors for hydrate crystal growth in multiphase transportation pipelines. On this basis, this paper presents a more practical and comprehensive bidirectional growth model of hydrate shells for an actual pipeline system. Thermodynamic phase equilibrium theory and water molecule penetration theory are applied in this model to develop a method for calculating the concentration change of hydrate-forming guest molecules and the permeation rate of water molecules. The temperatures on both sides of the hydrate shell are predicted by the heat transfer model. Simultaneously, decreasing the mass transfer coefficient with continuous hydrate growth is used to describe the problem in which the mass transfer efficiency decreases with a thickened hydrate shell. Then, the hydrate growth kinetic parameters of the pipeline system are optimized according to hydrate growth experiments conducted in a high-pressure flow loop and the microscopic characteristics of the particles were provided using the PVM and FBRM probes. The improved hydrate growth model can improve the prediction accuracy of hydrate formation in slurry systems.

Study of an ESP's performance handling liquid-liquid flow and unstable O-W emulsions part II: Coupled CFD-PBM modelling

The internal flow behavior of an ESP handling dispersed oil-water and emulsion flows remains quite unexplored. Previous studies have focused either on the individual droplet dynamics or on a simplified and limited modelling of the ESP's global performance. Hence, this study seeks to implement and analyze the applicability of a more robust and far-reaching CFD-PBM model which maintains a reasonable computational expenditure. Good agreement with experimental data was attained by the Eulerian-PBM framework (<10% error) and acceptable mean flow predictions were achieved with a less robust and computationally demanding VOF model (15% error). The internal flow behavior was noted to be governed by droplet size and effective viscosity variations, which induce the formation adverse pressure gradients leading to the emergence of backflow currents and eddies, particularly at higher oil fractions and lower flowrates. At higher flowrates and latter stages, well adapted flow is always attained, regardless of the mixture handled.

Seepage Characterization of Oil-in-Water Emulsion in Porous Media in Marine Sandstone Reservoirs

Interfacial tension is a crucial factor affecting emulsion flow behavior in porous media. Finding the emulsion flow properties under different interfacial tensions is important to the potential use of emulsion in field enhanced oil recovery (EOR) applications. In this study, oil-in-water (O/W) emulsions were first prepared with different interfacial tensions. Then, a set of sandpack flow experiments were conducted to study how the interfacial tension affects the plugging ability of oil-in-water (O/W) emulsion when flowing in porous media. After that, a regression model, which considered the interfacial tension factor for the first time, was developed using MINITAB to determine the emulsion plugging ability characterized by effective viscosity. The results show that the interfacial tension between oil and water in the O/W emulsion system had a significant effect on the emulsion plugging ability. The plugging pressure of emulsion in sandpacks increases with the increase in interfacial tension. This is probably because the strength of the film between oil droplets and water became higher as the interfacial tension increased. The newly developed regression model, which incorporates the interfacial tension effect to describe the emulsion effective viscosity in different sandpacks, has a good correlation with experimental data. From error analysis, the correlation coefficient R²ₐdⱼ and mean absolute relative error MAER between the calculated and experimental results are 0.994 and 4.64%, respectively. The regression model could be used for prediction for the O/W emulsion effective viscosity in porous media with relatively high accuracy.

Three-dimensional simulation of drop motion in channels of different cross-sections

Three-dimensional Boundary Element Method accelerated using a heterogeneous Fast Multipole Method is employed to study two-phase flow in a microchannel of different cross-sections. The flow of a mixture of two Newtonian liquids with equal viscosities and densities is described by Stokes equations. A comparison of the simulation results of the droplet dynamics in cylindrical capillaries with experimental data available in the literature was carried out and showed the qualitative agreement. The deformable droplet motion is considered in a channel with a circle, square, and hexagon cross-sectional shape. The influence of droplet size on a relative velocity in a channel is studied. The applied approach to numerical simulation can be used to solve a wide range of problems related to emulsion flows in microscales.

Emulsion-assisted thermal recovery method in heterogeneous oilsands reservoir

To prevent the steam from channeling and breakthrough in heterogeneous oil sands reservoirs, oil-in-water (O/W) emulsion is proposed and developed as a plugging agent in this study. However, one suspects that increased temperature destabilizes emulsion, promoting oil/water separation and thus to lose its plugging benefits induced by “Jamin effect”. This intuitive picture changes when the emulsion flows through heated porous media. In this paper, we show that increasing temperature enhances emulsion plugging effect, after a critical temperature reaches. O/W emulsions were firstly prepared at room temperature (~20 °C) individually using eight different surfactants and then injected in sandpacks at temperatures ranging from 20 °C to 140 °C. Experimental results show that the emulsion plugging strength at temperature of 140 °C is three times greater than that at room temperature (20 °C) and still shows a rising trend with temperature up to 140 °C. Measurements of the median droplet sizes of the effluents at different temperatures showed that there was no phase separation during the flow tests. This is because that the “snap-off” and “fingering induced break-up” processes keep the emulsion droplets dynamically stable during the flowing process. It is the changing hydrophilic-lipophilic characteristic of the surfactant molecules, as the temperature increases, that causes a parabola trend with a minimum of IFT and thus influences the emulsion plugging effect. What we expect following steam injection into the reservoir is that the achieved emulsion plugging strength could still be maintained or even enhanced so that the emulsion slug will not be easily displaced away by further steam injection, thus optimizing thermal recovery performance. By carefully selecting surfactant on the basis of its hydrophilic-lipophilic characteristic, an optimum emulsion system, contributing expected plugging strength at elevated temperatures, was designed, applied and verified for effective conformance control in heterogeneous parallel-sandpack. The experimental results demonstrate the designed emulsion can achieve conformance control in parallel-sandpack with a permeability ratio of 10 Darcy: 5 Darcy at room temperature and the conformance performance is still maintained as the temperature increases, up to 99 °C.

ABOUT THE CLASSIFICATION OF HEAVY HIGH-VISCOSITY OILS

Background When classifying oils by viscosity, a number of scientists have established their ambiguity and significant dependence on density. Therefore, these or those intervals of viscosity simultaneously include intervals on the density of oils. In this regard, it is quite obvious to study the dependence of the viscosity of oils with increased viscosity on their density. The construction of such dependences for vast regions of oil production would make it possible to obtain patterns and study the physicochemical nature of the viscosity of high-viscosity and super-viscous oils. Aims and Objectives The aim of the research is to obtain a statistical dependence of the oil viscosity on density and to establish the regularity of the influence of density on the rheological behavior of the fluid. The research tasks included the establishment of the characteristic boundaries of such dependence and the identification of the causes of its anomalies. Methods The studies were carried out on the basis of collected experimental data on measuring the viscosity of degassed anhydrous oils under standard conditions in various regions of the Russian Federation. Based on additional data on density, the dependences of viscosity on density were constructed using standard methods of statistical processing. Results It has been established that the dependence of the viscosity of oil at values in the range from 30 to 250 mPa · s on the density in the range of values from 880 to 930 kg/m3 has two almost linear sections, separated by a density value of about 910 kg/m3. The reason for the intensive increase in viscosity in the second section, obviously, on the one hand, is a significant increase in the content of molecules of heavy hydrocarbons - resins and asphaltenes in oils, forming associates of molecules and a certain spatial structure that resists flow; on the other hand, during the flow of such a liquid, the interaction of molecules associates with each other is possible, similar to the flow of concentrated water-oil emulsions with a water cut of more than 0.5 by volume, in which the increase in viscosity occurs due to inter-droplet interaction in the flow.

The numerical study of the flow regimes of two-phase oil and displacing agent mixtures in straight microchannels simulating a pore or crack in the rock formation

The calculated study of the flow regimes of two-phase oil and water mixture in straight microchannels simulating a pore or crack in the rock formation was carried out. It was shown as a result of the literature survey that all modern, industrially developed methods of the oil recovery from the oil reservoirs is considered as unsatisfactory in all oil-producing countries. The average value of the final oil recovery is varied from 25% to 45%, so, it is easy to count, that residual or unrecoverable oil reserves in the subsoil reach an average of 55-75% of their initial values. Also, it was found, that the use of micro and nanotechnologies in a broad sense is one of the possible and promising ways to solve these problems. A numerical method called «Volume of Fluid» (VOF) was used to simulate the two-phase flows of oil and displacing agents in the considered microchannels. It was proposed to use the dimensionless number, called Regime number, to describe the different flow regimes of oil/water mixture and transitions between these regimes. The plug flow, the slug flow, the parallel flow and the emulsion flow regimes were observed.

A CFD modeling of oil-water flow in pipeline: Interaction analysis and identification of boundary separation

The aim of this study is to simulate the flow of emulsion (immiscible liquids) which is a complex phenomenon in the petroleum industry. In this study, three types of emulsions (O/W) were simulated using by CFD which has been applied to predict the interaction behavior of oil with water for different emulsions (25%O–75%W, 50%O–50%W and 75%O–25%W). Numerical modeling illustrated that the obtained results of the velocity profiles were very good agreement with the experimental data for three type of emulsions. In addition, the analytical model of interaction analysis and identification of boundary separation for two-phase flow approve with the experimental data available, despite the emulsions remain to be more difficulty due to the complex chemical reactions. The results of this study can provide the best solutions for corrosion during hydrocarbons transportation. Thus, CFD approach is recommended to use for numerical investigates due to the high accuracy.

Micro-mechanism analysis of the rheological properties of water-in-waxy-crude-oil emulsion under pipe flow

Flowing experiments with different water contents in water-in-waxy-crude-oil emulsions were performed in a flow loop apparatus. The real-time variations of rheological properties and microscopic distributions of the emulsions over time during pipe flow were quantitatively analyzed. It was found that the emulsification effect of the emulsion is enhanced due to shear effect, resulting in an increase of gel point and viscosity over time. The average increments in the gel point are approximately 1.5 °C, 1.7 °C and 1.9 °C for the emulsions with water contents of 10%, 20% and 30%, respectively. During the experimental period from 0.5 h to 18 h, the average viscosities measured at the emulsion temperature increase by 31%. Characterization parameters of number-averaged diameter (d 1,0), specific surface area (SA) and polydispersity (PDI) were applied to reflect the microstructure of emulsions from the perspectives of droplet size, dispersity and nonuniformity. The water droplets become smaller and uniformly dispersed as the pipe flow goes on. The Gibbs free energy increases as the emulsion flows through the pipe, which is mainly caused by the shear of the pipe wall. The van der Waals force increases from −0.0678 × 10−21 J to −1.7657 × 10−21 J as the emulsion’s water content changes from 10% to 30%. The water droplets can promote crystallization of wax crystals by offering the necessary nucleus surface. Furthermore, the coexistence of water droplets and wax crystals creates a synergistic effect, which can augment the total energy and structural strength of the emulsion system.

Experimental investigation on the performance of Electrical Submersible Pump (ESP) operating with unstable water/oil emulsions

Electrical Submersible Pump (ESP) is one of the most commonly used artificial lift methods in petroleum production, due to its capacity to operate in several conditions with two or three-phase flows. When the ESP operates with emulsion flow, its performance is degraded, and operational instabilities occur. Therefore, this paper aims to carefully investigate phase inversion and to present, by the first time, the effective viscosity of unstable mineral oil/water emulsions, within the ESP. The first part of this work analyzes the phase inversion phenomenon for two oil types in three viscosities, five ESP rotational speeds, and three mixture flow rates. Logistic functions were fitted using the dimensionless head as a water cut function to determine the phase inversion within the ESP. The continuous phase inversion model, developed for emulsion pipe flow, did not present a satisfactory agreement to flow conditions tested. An indirect method to determine the emulsion effective viscosity within the ESP was proposed, which was obtained from the water/oil emulsion performance curves. The viscous performance data were used to determine the parameters of a dimensionless head empirical model for the tested ESP. Thus, the calculated values were compared with the effective viscosity obtained with oil and water emulsions, as well as the ESP performance, operating with emulsion and oil, which provides similar values for low rotational speeds. The different behavior of the effective viscosity between the pipeline flow and within the ESP was observed for water-in-oil emulsions and may be related to the high centrifugal field in the ESP.

Numerical investigation of bubble diameter in branched microchannel

With growing importance of microchannel in notable fields like medical, aerospace, food industry, it is necessary to improve the accuracy of pre-determining the mean droplet size to its maximum. We have analysed the various parameters that can influence the bubble size formed. Our main objective is to derive a relationship between diameter of microchannel, length of the junction, emulsion flow rate, and mean droplet diameter so that we would be able to determine the emulsion properties beforehand. It was found that bubble size increases as flowrate of continuous phase decreases.

Modeling and experimental data of the flow of highly concentrated emulsions in porous media

This paper gives a theoretical model which allows to predict changes of the blockade of the porous bed during the flow of non-Newtonian emulsions. It takes into account much more process and material parameters than the formulas published in the literature till now: like size of dispersed phase droplets, emulsion concentration and rheological parameters of heterogeneous, non-Newtonian liquid. Using the model it is also possible to predict changes of bed permeability, its blockade, as a result of oil droplets capture. Model calculations were verified with experimental data and satisfactory correctness was obtained. The work contributes to the development of the description of the transport of multiphase substances, with complex rheological properties, through porous structures. The results of the research may find practical application during the development of methods of intensifying oil production, as well as the assessment of the penetration of complex pharmaceuticals in dermal structures.

Flow behaviors of emulsions in constricted capillaries: A lattice Boltzmann simulation study

We study the flow behaviors of emulsion droplets in constricted capillaries using a surfactant Lattice Boltzmann model. We first establish the model by introducing a surfactant component into the pseudopotential multiphase model and characterizing the amphiphilic structure using dipoles. Then we study the flow of emulsion droplets in single or parallel capillaries. The simulations show that single droplet can pass through single throat in three ways, i.e., passing directly, passing with deformation, and snap-off. Multiple droplets may flow through the capillary with coalescence, and can also block the throat by adsorption or bridging, which may induce upstream flow caused by buoyancy. There is a “trap effect” when emulsions flow through parallel throats, and the droplet could be pinched off by obstacles, while the surfactants can inhibit the droplet breakup due to Marangoni effect. The simulations present detailed flow behaviors at pore scale and provide new insights for emulsion flow modeling.

Water permeability of geopolymers emulsified with oil

Recently, geopolymer (GP) cements have proven adequate to immobilize oil emulsions as GEOIL composites. When used for radioactive waste storage, the vicinity of GEOIL with Portland Cement (PC) concretes may induce leaching by the PC pore water. This research identifies the preferential water flow pathways, and quantifies the water permeability of hardened GEOIL mortars using a typical PC pore water. Two alkali-activated GP cements are used, either made of 100% metakaolin (MK) or of 80%MK-20% slag, for oil proportions of 0, 20, 40 or 60%vol.For the identification of the preferential water flow pathways, two water flow scenarii are investigated numerically. Either water flows through the oil emulsion (Scenario 1) or water flows through the GP cement mortar pores (Scenario 2). The 3D structure of the oil emulsion is quantified by X Ray micro-computed tomography (X Ray micro-CT), and the pore structure of GP cement mortars is identified by image analysis. Fluid pathways are predicted for both scenarii by 3D numerical simulations. Secondly, water permeability experiments are conducted on GEOIL mortars. Water permeability Kwater of highly alkaline PC water is deduced over several weeks. The results validate Scenario 2; for 20 or 40%vol oil, water flows preferentially through the GP cement mortar pores (at a permeability below 10−18 m2), instead of through the percolating oil emulsion.Finally, experiments show that Kwater for the GP cement mortar made of 80%MK-20%GGBFS does not remain stable over time when added with 20%vol oil. Comparatively, for the 100%MK GP cement mortar with 20%vol oil, a stable Kwater is recorded for 40 days. Whatever the oil percentage, the initial Kwater value is identical and smaller than without oil. A dedicated experiment shows that the oil additives (surfactants) are very probably responsible for this behaviour. At 60%vol oil, water and organic matter flow progressively out of the GEOIL composite.