Transient Interfacial Tension Research Articles

Model selection for dynamic interfacial tension of dead crude oil/brine to estimate pressure and temperature effects on the equilibrium tension

Interfacial tension (IFT) measurements using pendant drop techniques are typically time-dependent and embed the underlying physics that can be exploited. A physics-based modeling approach of the time-varying IFT is chosen to estimate the equilibrium IFT and to identify which phenomena are leading the dynamic. This approach is both consistent and reproducible, hence advantageous for routine research and industrial applications because typical approaches are especially challenging when the techniques rely on long-time measurements or detailed characterization of phase composition and transport properties. The approach is applied to the Brazilian pre-salt dead crude oil/brine system when the equilibrium between the phases and between bulk and interface concentrations are not assured initially. Selected models based on a different physical phenomenon, mainly focused on diffusion and sorption, and with a particular time scale behavior are tested on measured data. The model which better fits the data in its full-time range should point out which phenomenon is dominant. The results indicate that the model with t time scale seems preferable for this oil/brine system, which is associated with a diffusion-controlled process in multiple regimes, for instance, bulk-to-interface diffusion of naturally present interface chemicals and their rearrangement at the interface. The effect of pressure (14.7 psi–4000 psi) and temperature (22 °C–60 °C) variations on the equilibrium IFT of the Brazilian pre-salt reservoir dead crude oil/brine at various conditions is characterized and discussed using the consistent physics-based estimate for the equilibrium IFT. The results show that the equilibrium IFT does not change significantly with pressure and increases with temperature, further supporting the identified presence of naturally present interface chemicals in the transient IFT measurements and the brine ionic valence influence. Furthermore, the wettability of carbonate rock samples with different mineralogical compositions to the dead crude oil/formation water is assessed using adhesion tension which embeds both IFT and contact angle contributions. Pressure changes do not affect wettability considerably, while the effects of temperature increase show that every sample tended to be wetter to its respective fluid affinity, following the IFT temperature behavior.

New insights into the interfacial phenomena occurring between hydrocarbon solvent and heavy oil

Solvent injection is an alternative method for heavy and extra heavy-oil recovery in situations where thermal methods cannot be applied, such as thin reservoirs, wormholed reservoir after-CHOPS (cold heavy-oil production with sands), or fractured reservoirs. Solvents normally exist in their liquid or supercritical phase under reservoir conditions and may not be miscible with heavy-oil at first contact. Coupling with the fact that diffusion into highly viscous fluids tends to be very slow and an interface exists in the first contact of liquid solvent and oil, displacement by capillary imbibition may take place. This displacement eventually improves the contact area between oil and solvent resulting in an enhanced mixing process by diffusion.To understand this phenomenon and fully capture the interaction of solvent and heavy-oil in different rock systems, experimental investigations were conducted using sandstone and limestone core samples. The samples saturated with different types of oils (viscosities ranging between 14 and 170,000 cP) were immersed into a tube filled with different types of solvent (propane, heptane, decane, and naphtha). Two characteristics of the experiments, namely the areal coverage as a measure of capillary imbibition and the rate of color change as a measure of diffusion, were used to analyze the imbibition-diffusion process. Both the color change of the solvent surrounding the rock and the amount of oil expelled from said rock were used to analyze the interaction process to identify the existence of a transient interfacial tension period and the effect of coupling imbibition and diffusion processes on the interaction qualitatively (visually) and quantitatively. The color change of the medium surrounding the core (becoming darker) points to the prominence of diffusion over capillary forces.We observed that in the solvent/heavy-oil system, in which molecular diffusion is a slow process, a dynamic (or transient) interfacial tension (TIFT) exists before fully mixing. During this period, both imbibition and diffusion become effective––acting symbiotically, and depending on the oil/solvent viscosity ratio, the period may dominate a great portion of the whole process. This critical viscosity ratio was found to be 20,000–50,000––corresponding to a viscosity range of 30,000–50,000 cP. For this range of oil viscosities, a medium carbon number (typically heptane) was observed to be the most effective solvent to yield the most efficient TIFT type interaction.

Determination of transient interfacial tension in a microfluidic device using a Laplace sensor

In two-phase dispersion processes coupled with interphase mass transfer, the interfacial tension varies with the mass transfer and significantly affects the dispersion. Determination of the transient interfacial tension (TIFT) in such processes could facilitate better understanding and optimization of the existing processes. In this study, a microfluidic device in which a Laplace sensor was used as a pressure probe was developed to determine the TIFT. The developed Laplace sensor was shown to allow accurate measurement of the local pressure in a micro-device, and to be superior to a commercial pressure sensor. The new method can be used to precisely determine the interfacial tension when the dispersion rate was not higher than 1.5 Hz, and to have a measurement range not narrower than 0.17–58.53 mPa·s. The TIFTs of several systems were then determined, and a mathematical model was established to predict the results. The main factors governing the TIFT were analyzed based on both the experimental and theoretical results.

Rheological surface properties of commercial citrus pectins at different pH and concentration

The interfacial activity of commercial low-methoxy (LM) and high-methoxy (HM) pectins from citrus peel was investigated at air-water interfaces by focusing on the role of their molecular weight (MW) and degree of methoxylation (DM). A pendant drop tensiometer was used to carry out transient interfacial tension measurements and small amplitude oscillations. Different pectin concentrations (ranging between 0.00001 g/100 g and 5 g/100 g) and pH conditions (4 and 6) were used during the tests. It was observed that citrus pectins are characterised by interesting surface properties that could allow potential practical uses. Experimental results evidenced that MW affects the diffusion of molecules towards the interface, whereas other investigated parameters (i.e. surface tension, adsorption rate, dynamic moduli) seem more dependent on DM and a clear dependence on MW was not observed. pH conditions modify intermolecular interactions in the bulk and surface layer, even if their effects are related to the fraction and distribution of carboxylic groups along the chain. As a consequence, a complex dependence on investigated parameters was observed and no clear relationship was obtained. Nevertheless, among tested commercial samples LM pectins exhibited the most interesting properties and this behaviour seems related to the intermolecular interactions occurring among them.

Effect of polymer on dynamic interfacial tensions of sulfobetaine solutions

The effect of different types of polymers, partly hydrolyzed polyacrylamide (HPAM), hydrophobically modified polyacrylamide (HMPAM) and co-polymer, on the dynamic interfacial tensions (IFTs) of benzyl substituted alkyl sulfobetaine (BSB) against n-alkanes, kerosene and crude oil have been investigated by a spinning drop interfacial tensiometer. The influence of polymer concentration on IFTs was expounded. The experimental results show that betaine has high interfacial activity and the addition of polymer has great influence on both dynamic IFT behaviors and equilibrium values between surfactant solution and n-alkanes mainly by modifying the interfacial molecular arrangement on the interface. However, the addition of polymer affects the dynamic IFTs of surfactant solution against kerosene and crude oil, but has little effect on the equilibrium IFT values. Active substances existing in kerosene and the in situ produced petroleum acidic soaps play a synergistic effect with betaine to reduce the IFTs. The increase of viscosity of aqueous phase caused by polymer influence the adsorption of the surfactant at the interface, slowing down the decrease of IFTs and changing the minimum transient IFT values.

Effect of Steam-Assisted Gravity Drainage Produced Water Properties on Oil/Water Transient Interfacial Tension

Steam-assisted gravity drainage (SAGD) produced water (PW) consists of oil, solids, clays, petroleum-derived compounds, and other dissolved organic matters (DOMs), which make the SAGD PW highly stable and, therefore, very hard to treat. Developing a correlation between SAGD PW properties and dynamics of interfacial tension (IFT) between dispersed and continuous phases is important to understand the coalescence of dispersed phase droplets, which, in turn, leads to demulsifications of these difficult emulsions produced during SAGD operations. This work sheds light on the interfacial activity of SAGD PW endogenous surfactants, humic acids (HAs), as well as the interaction dynamics of these compounds with naphtha-diluted Alberta oil sand bitumen (AOSB) present in a model SAGD PW. We quantify the dynamics of the IFT of a naphtha-diluted AOSB oil drop in pure water as well as SAGD synthetic brine. Our results pinpoint the distinctive influence of the percentage weight composition of the naphtha-diluted AOSB and the surrounding model SAGD PW pH on the dynamics of this oil–water IFT. We anticipate that the results of this study will bring about a better understanding of interfacial film properties, leading to a predictable coalescence mechanism in SAGD PW emulsions, facilitating the design of next-generation SAGD deoiling unit operations.

Study on the transient interfacial tension in a microfluidic droplet formation coupling interphase mass transfer process

In two‐phase dispersion coupling interphase mass transfer process, the variation of interfacial tension is an important factor affecting the dispersion. In this study, we described a microfluidic method for the determination of the transient interfacial tension (TIFT). The method has the advantage of determining TIFT during the whole droplet formation process, rather than only at the rupture moment as reported in previous studies. The TIFTs of several systems were determined. In certain systems, it has been found that the droplet size decreased with the increase of the dispersed phase flow rate, which is obviously different from the constant interfacial tension system. It has also been found that TIFT was mainly affected by two‐phase flow rates, solute type and concentration, and droplet size. A semiempirical equation was finally established to predict TIFT. It has the potential to be used in a variety of industrial equipment with dispersion–mass transfer coupling process. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2542–2549, 2016

Multiphase flow of miscible liquids: jets and drops

Drops and jets of liquids that are miscible with the surrounding bulk liquid are present in many processes from cleaning surfaces with the aid of liquid soaps to the creation of biocompatible implants for drug delivery. Although the interactions of immiscible drops and jets show similarities to miscible systems, the small, transient interfacial tension associated with miscible systems create distinct outcomes such as intricate droplet shapes and breakup resistant jets. Experiments have been conducted to understand several basic multiphase flow problems involving miscible liquids. Using high-speed imaging of the morphological evolution of the flows, we have been able to show that these processes are controlled by interfacial tensions. Further multiphase flows include investigating miscible jets, which allow the creation of fibers from inelastic materials that are otherwise difficult to process due to capillary breakup. This work shows that stabilization from the diminishing interfacial tensions of the miscible jets allows various elongated morphologies to be formed.

Viscosity scaling of fingering instability in finite slices with Korteweg stress

We perform linear stability analyses and direct numerical simulations to investigate the influence of the dynamic viscosity on viscous fingering instability in miscible slices. Selecting the characteristic scales appropriately, the importance of the magnitude of the dynamic viscosity of individual fluids on viscous fingering in miscible slice has been shown in the context of the transient interfacial tension. Further, we have confirmed this result for immiscible fluids and shown the similarities between viscous fingering in immiscible and miscible slices with transient interfacial tension. In a more general setting, the findings of this letter will be very useful for different viscous flows, such as displacement of a buoyant miscible layers in a vertical Hele-Shaw cell, viscous fingering instability with viscosity-dependent dispersion, etc.

Effect of organic alkali on interfacial tensions of surfactant solutions against crude oils

Abstract The dynamic interfacial tensions (IFTs) of petroleum sulfonate and organic alkali combined solutions against crude oils with different acid numbers have been investigated by a spinning-drop interfacial tensiometer. The influences of surfactant concentration, organic structure and concentration on the IFTs were expounded. The experimental results show that the petroleum acids can react with the organic alkalis and produce the surface-active soaps at the interface in situ. Both the ultralow transient and equilibrium IFTs can be reached at optimum conditions. The structures and contents of petroleum acids play important roles in controlling IFTs between the crude oils and the organic alkaline solutions. It is believable that fatty acids contribute to the lower transient IFT in short time and aromatic acids with condensed ring determine the equilibrium IFTs. The crude oil with higher acid number usually shows lower IFT values, however the structures of petroleum acids are more crucial factors and the crude oils with similar acid numbers may behave quite different dynamic IFT behaviors. The concentrations and structures of organic alkalis also strongly affect the IFTs of crude oil–alkaline solution systems. An obvious IFT minimum appears as a function of organic alkali concentration and the increase of molecular size of the organic counterion results in a loosely packed film and an increment of IFT. By adding petroleum sulfonate to organic alkaline solutions, the IFTs may be easily reduced to an ultralow value through the formation of close-packed mixed adsorption film containing surfactant, petroleum acid and soap molecules. For organic alkalis with larger molecular size, the loose mixed adsorption film is beneficial for the synergistic effect among petroleum acids, soaps and surfactant molecules, which can enlarge the applying reservoirs of organic alkali.

Synthesis of Internal Olefin Sulfonate and its Application in Oil Recovery

Hexadecyl internal olefin sulfonate was synthesized using sulfur trioxide and internal olefin by sulfonation reaction. The internal olefin sulfonate was characterized by FT-IR and MS methods. Surfactant mixtures were formulated by internal olefin sulfonate and octadecyl hydroxysulfobetaine. It was found that the surfactant mixtures could lower the transient interfacial tension to ultra low values in the presence as well as the absence of polymer. Injection of 0.3 PV (pore volume) of the formulated slug followed by chase water, 15.15 % incremental recovery was obtained over water flood, accomplishing a final oil recovery of 64.78 % original-oil-in place.

Experimental Study of the Interaction between NaOH, Surfactant, and Polymer in Reducing Court Heavy Oil/Brine Interfacial Tension

The effect of the surfactant, NaOH, and polymer and the interactions between them on the heavy oil/water interface are unveiled by studying the dynamic interfacial tension (IFT), minimal transient IFT, and total organic carbon (TOC) and analyzing the phenomenon during the measurement of IFT of heavy oil/different alkaline systems, including alkaline (A), alkaline–surfactant (AS), alkaline–polymer (AP), and alkaline–surfactant–polymer (ASP). The results show that there exists a minimum transient IFT. There is an optimal composition to achieve the minimal IFT with varying NaOH concentrations in 0.018–0.8 wt %. For different chemical solutions, the optimal composition is different. Adding polymer affects the IFT by influencing the diffusion of species to or from the interface. Despite polymer addition, adding surfactant will increase the IFT at a lower alkaline concentration because of its competitive adsorption with OH– and reduce the IFT at a higher alkaline concentration because of its synergistic effect....

The effect of surfactant type on the rheology of ovalbumin layers at the air/water and oil/water interfaces

The aim of this work is to investigate the simultaneous adsorption of a globular protein, ovalbumin, and two different types of food emulsifiers, non-ionic Tween 60 and anionic Admul DATEM, at the air–water and sunflower oil–water interfaces. A commercial non-purified oil was used, aiming at investigating the behaviour of interfaces close to real systems. A pendant drop tensiometer was used to carry out transient interfacial tension measurements and small amplitude oscillations. A constant protein concentration (0.1 g/l) and different emulsifier/protein ratios (ranging between 0 and 0.6) were used during the tests.Experimental results evidenced that the non-ionic emulsifier replaces the protein on the interface (only a partial replacement was observed in the tested conditions) whereas the anionic molecule interacts with the protein forming complexes which can be almost completely replaced by the single emulsifier.The interfacial layers are characterised by a prevalent solid-like behaviour, which proved to be similar to 3D weakly structured systems. The rheological properties are strongly dependent on the nature of both the emulsifier and the interface, nevertheless it was observed that ovalbumin yields a more structured and stronger layer than Admul and Tween. In mixed systems, increasing the emulsifier concentration, the extension of this 2D network decreases whereas the strength seems to be less dependent and evidences only a slight reduction for Admul addition at the A/W interface.

Novel Alkyl Ether Sulfonates for High Salinity Reservoir: Effect of Concentration on Transient Ultralow Interfacial Tension at the Oil–Water Interface

AbstractThe effect of surfactant concentration on the occurrence and detection of transient ultralow interfacial tension (IFT) between crude oil and formation water at 75 °C has been investigated using a series of novel sodium alkyl ether sulfonates having various increasing molecular weights and degrees of ethoxylation. All surfactant systems displayed dynamic interfacial tension (DIT). Transient ultralow DIT (DITmin) were detected only within an intermediate surfactant concentration. This behavior was attributed to an implicit concentration‐related length scale required for the added surfactant to diffuse from the bulk phase to the freshly prepared oil–water interface. In the high surfactant concentration range, this length scale is relatively short and results in an instantaneous (and undetectable) occurrence of DITmim in a relatively very short time scale, well beyond the detection limit of the spinning drop tensiometer (~2–3 min). Interestingly, DITmin were detected only in systems above the surfactant's critical micelle concentration, suggesting that DITmin occurs as a result of the diffusion (subsequent to the adsorption) of the oil acidic species from the interface to the bulk phase to form mixed micelles with the added surfactant. Measurements of DITs in the presence of decane showed no evidence for DITmin, confirming the general belief that DITmin is indeed due to the interaction of the added surfactant with the oil acidic components. Finally, the effect of surfactant concentration on the equilibrium IFT (γeq) showed evidence for relatively low values (~10−2 mNm−1) for some surfactant systems.

Effects of partial miscibility on drop-wall and drop-drop interactions

The effect of the mutual diffusion of two polymeric phases on the interaction and coalescence of two nearby drops in quiescent conditions is investigated for two partially miscible systems, differing in the miscibility of the components. Transient interfacial tension measurements show that the polybutene (PB)/polydimethylsiloxane (PDMS) system is highly diffusive in terms of diffusing low-molecular weight species, while the polybutadiene (PBD)/PDMS system is less miscible. Drops of the highly diffusive PB/PDMS system at distances closer than their equivalent radius attract each other and coalesce with a rate that, in the last stage of the coalescence process, is the same for all drop combinations. For the slightly diffusive PBD/PDMS system, no coalescence occurs, and, in contrast, repulsion between the drops is observed. These phenomena are qualitatively explained in terms of the overlap of diffuse layers formed at the drop surfaces of two, close enough drops, yielding concentration gradients that cause gradients in the interfacial tension. These gradients yield Marangoni stresses that induce flow leading either to attraction or repulsion. To determine whether Marangoni stresses are strong enough to displace a drop in quiescent conditions, single drops of PB and PBD are placed in a PDMS matrix in the vicinity of a wall. A lateral drop motion toward the wall is observed for the highly diffusive PB/PDMS system only, while PBD drops do not move. The diffuse-interface model is considered as a good candidate to capture these phenomena described since it couples the mutual diffusion of the low-molecular weight component with both drop and matrix, while including hydrodynamic forces. The presented numerical simulations indeed show a diffusion-induced macroscopic motion that qualitatively reproduces the experimental phenomena observed and support our interpretations.

Transient interfacial tension and morphology evolution in partially miscible polymer blends

The influence of molecular weight asymmetry across an interface on the transient behavior of the interfacial tension is investigated for two different polymer combinations, polybutadiene (PBD)/polydimethylsiloxane (PDMS) and polybutene (PB)/PDMS. This choice ensures a minor diffuse interface using the first combination and a very diffuse interface in the latter case. Measurements of the interfacial tension as a function of time are carried out using a pendent/sessile drop apparatus at different temperatures ranging from 0 °C to 80 °C. Variations in the transient interfacial tension are attributed to diffusion of the lower molecular weight components from one phase into the other and the most pronounced changes are measured for the most diffusive systems (low molecular weight and high polydispersity) when diffusion goes from the drop into the matrix. By reversing the phases, only minor changes in the transient interfacial tension are measured. This is due to a fast saturation of the drop-phase since the drop volume is much smaller than that of the continuous phase. In all cases investigated, after a sufficient time a steady value of the interfacial tension is reached. In order to estimate the characteristic diffusion times of the migrating species, a discrete solution of the diffusion equation and a kinetic model from literature are applied. Results obtained are in line with the experimental observations. The importance of a changing interfacial tension on morphology development is studied on dilute (1%) blends, using two in situ techniques: small angle light scattering (SALS) and optical microscopy (OM). The SALS patterns yield the time evolution of the drop size, which is subsequently compared with the morphology following from OM. Depending on the diffusivity of the system, the morphology development is dominated by either diffusion or coalescence. Existing sharp-interface drainage models indeed do not apply for the diffuse blends and an improved quantitative estimation of the value of the critical film thickness is needed.

Transient interfacial tension of partially miscible polymers

The interfacial tension of three different binary polymer blends has been measured as function of time by means of a pendent drop apparatus, at temperatures ranging from 24 ° C to 80 ° C . Three grades of polybutene (PB), differing in average molecular weight and polydispersity, are used as dispersed phase, the continuous phase is kept polydimethylsiloxane (PDMS), ensuring different asymmetry in molecular weight across the interface. The interfacial tension changes with time and, therefore, this polymer blends can not be considered fully immiscible. Changes in interfacial tension are attributed to the migration of low-molecular weight components from the source phase into the interphase and, from there, into the receiving phase. In the early stages of the experiments, just after the contact between the two phases has been established, the formation of an interphase occurs and the interfacial tension decreases with time. As time proceeds, the migration process slows down given the decrease in driving force which is the concentration gradient and, at the same time, molecules accumulated in the interphase start to migrate into the “infinite” matrix phase. A quasi-stationary state is found before depletion of the low-molecular weight fraction in the drop occurs and causes the interfacial tension σ ( t ) to increase. The time required to reach the final stationary value, σ stat , increases with molecular weight and is a function of temperature. Higher polydispersity leads to lower σ stat and a weaker dependence of σ stat on temperature is found. A model coupling the diffusion equation in the different regimes is applied in order to interpret the experimental results. Numerical solutions of the diffusion equation are proposed in the cases of a constant and a changing interphase thickness. In the latter case, the interphase is defined by tracking with time a fixed limiting concentration in the transient concentration profiles and the variations found in σ ( t ) are attributed to the changes in the interphase thickness. A discrete version of this continuous model is proposed and scaling arguments are reported in order to compare the results obtained with the predictions of the continuous model. The kinetic model as proposed by Shi et al. [T. Shi, V.E. Ziegler, I.C. Welge, L. An, B.A. Wolf, Macromolecules 37 (2007) 1591–1599] appears as a special case of the discrete model, when depletion is not taken into account. Using the models, time scales for the diffusion process can be derived, which fit the experimental results quite well.

Synthesis and Interfacial Properties of Dialkylbenzenesulfonates for Producting Low Interfacial Tensions

Abstract A new method of synthesis a series of pure dialkylbenzene sulfonates is described. The benzene ring carries a major alkyl substituent, consisting of a linear chain of sixteen carbon atoms long, and one additional methyl group. Products are charactered by EI-MS and 1H NMR. Experimental investigations have been conducted to explore the interfacial tension behavior of crude oil with dialkylbenzenesulfonates. The effects of various parameters such as surfactant concentration, salinity concentration on the interfacial tension of crude oil-water were investigated in detail. The transient low interfacial tensions in crude oil/alkali system were caused by the synergistic effects between surfactant and the active species generated at interface, but surfactant molecules plays the dominant role at equilibrium.

Kinetics of Interfacial Reaction between Two Polymers Studied by Interfacial Tension Measurements

The reaction kinetics between carboxylic-terminal polybutadiene (PBd-COOH) and amino-terminal polydimethylsiloxane (PDMS-NH2) has been studied at the PBd/PDMS interface by measuring changes in interfacial tension during the reaction and inferring concentrations of the PDMS-NH3OOC-PBd complex reaction product by an application of the Gibbs adsorption equation. The time-dependent concentration of complex is obtained from the transient interfacial tension and follows a single-exponential growth function at low surface coverage, indicating first-order reaction kinetics.

Design and Application of an Alkaline‐Surfactant‐Polymer Flooding System in Field Pilot Test

We have developed an inexpensive sort of flooding reagent whose major components are natural mixed carboxylates from proportionally mixed saponification residuals of cottonseed oil, tea oil, vegetable oil, and soybean oil. An orthogonal test design method was used to select one form of this flooding reagent (which is named SD) by measuring the phase behavior and another form of the flooding system: alkaline/surfactant/polymer (named SD‐ASP). The optimal composition was obtained by measuring the transient interfacial tension (IFT) at the crude oil/aqueous interface. Results of the tests show that the SD‐ASP flooding systems are tolerant to salt up to 1.5×105 mg/L and to Ca2+ and Mg2+ to 5.0×103 mg/L at 90°C, the IFTmin (the minimum of IFT) is 10−3 mN/m, and the oil recovery ratio reaches 22.77% by using the core flood experiment. The pilot tests, including a putting in and sending out in a single oil well, a group oil well and a larger well region, were all very successful, with an average input‐output ratio of 1∶4.15. All these results demonstrate that the SD‐ASP formulation is a new, very inexpensive, and highly effective flooding system.