Surfactant Solution Flow Research Articles

Dissimilar turbulent momentum and heat transfer associated with viscoelastic vibration in channel flow

This experimental study on the momentum and heat transfer in drag-reducing turbulent channel flow of surfactant solution, i.e., viscoelastic fluid, has revealed a viscoelastic vibration (VEV) as a novel type of ordered turbulent motion in the wall vicinity where the elastic energy is transformed into turbulent kinetic energy. The VEV is a wave-like motion of low-frequency modes in the streamwise direction and causes zero average Reynolds shear stress. However, thermal diffusion occurs continuously due to the movement of a fluid lump owing to the VEV via the additional action of pressure.

An Imaging Technique For Characterizing Viscoelasticity Of Drag-Reducing Solutions

Existing rheometric measurement techniques that use load and displacement sensors are unable to resolve the non-Newtonian features of dilute drag-reducing solutions. In the present investigation back-lit particle image velocimetry, or particle shadow velocimetry, was used to quantify the complex dynamics of these fluids in a novel flow geometry. The flow of three non-Newtonian solutions were investigated in a periodically constricted tube (PCT). The radius of the tube walls was sinusoidal with respect to the streamwise direction. The three fluids under consideration were aqueous solutions of a flexible polymer, rigid polymer and surfactant, all of which were previously shown to instill drag reduction in a high Reynolds number, turbulent channel flow. Three solutions with mass concentrations of 0.01%, 0.03% and 0.05% were considered for each additive. Steady shear viscosity measurements demonstrated that all rigid and flexible polymer solutions were noticeably shear-thinning, while the surfactant solutions had a water-like shear viscosity. Each solution was measured at five Reynolds numbers between approximately 1 and 100 within the PCT. Relative to Newtonian fluids within the PCT, the rigid polymer solutions produced a plug-like flow with a blunted velocity and attenuated vorticity at radial coordinate further from the tube centerline. The flexible polymer solution, known to have appreciable amounts of elasticity, demonstrated a distinct chevron shaped velocity contour, coupled with a negative vorticity pattern within the contraction regions of the PCT. Despite having a seemingly Newtonian shear viscosity, the surfactant solutions produced velocity and vorticity patterns reminiscent of the flexible polymer. The general implication is that surfactants share similar elastic traits as flexible polymers. The vorticity transport equation was used to derive distributions of the non-Newtonian torque, more commonly called the `polymer torque' in other literature. It was revealed that the non-Newtonian torque was the source of vorticity field disruption in the flows of flexible polymer and surfactant solutions.

Modification of turbulence caused by cationic surfactant wormlike micellar structures in two-dimensional turbulent flow

An experimental study is performed to investigate the effects of the extensional rheological properties of drag-reducing wormlike micellar solutions on the vortex deformation and turbulence statistics in two-dimensional (2-D) turbulent flow. A self-standing 2-D turbulent flow was used as the experimental set-up, and the flow was observed through interference pattern monitoring and particle image velocimetry. Vortex shedding and turbulence statistics in the flow were affected by the formation of wormlike micelles and were enhanced by increasing the molar ratio of the counter-ion supplier to the surfactant, ξ, or by applying extensional stresses to the solution. In the 2-D turbulent flow, extensional and shear rates were applied to the fluids around a comb of equally spaced cylinders. This induced the formation of a structure made of wormlike micelles just behind the cylinder. The flow-induced structure influenced the velocity fields around the comb and the turbulence statistics. A characteristic increase in turbulent energy was observed, which decreased slowly downstream. The results implied that the characteristic modification of the 2-D turbulent flow of the drag-reducing surfactant solution was affected by the formation and slow relaxation of the flow-induced structure. The relaxation process of the flow-induced structure made of wormlike micelles was very different from that of the polymers.

Dependence of pressure drop on surfactant solution flow rate in foam coreflooding experiments through 50 mD limestone

The pressure drop (dP) and apparent viscosity characterize the ability of foam to control gas mobility in core flooding experiments. There is no clarity regarding which factor, total flow rate (qt), foam quality (fg), gas (qg) or liquid (ql) flow rate, determines the dP. The inconsistency in interpretation can be caused by the differences in conditions of experiments, which are carried out at one fixed and other varying parameter. In this study, dP and length of foam drops at the outlet are measured in three types of experiments at 400 and 500 psi for comparison: 1) scans at fixed total flow rate and varying fg; 2) tests at fixed liquid flow rate and varying gas flow rates; 3) tests at fixed gas flow rate and varying liquid flow rates. In foam scans 1, the dP measured at two qt decreased almost linearly due to low foamability starting at fg = 0.3, indicating a high quality regime. The length of foam drops and the bubble size increased with the increase in fg. In tests 2 and 3, there was no direct relationship between dP and qg at a constant ql, but dP increased with increasing ql at constant qg, which is in line with other publications. In addition, there was no direct dependence of the foam texture on the increase in qg and ql. The discrepancy in the dependence of dP on ql and qg between the three experiments was due to the fact that different combinations of ql and qg used in tests 2 and 3 resulted in the same fg and qt, which led to data overlap and data distribution in both high and low regimes. Meanwhile, dP measured in all three experiments was a linear function of the liquid flow rate with a line slope equal to the outlet pressure, regardless of the total flow rate. Due to the mathematical expression, the equation dP = P · ql can be called the equation of ideal foam and used as a test case for further comparisons. Thus, ql is the governing factor in high quality regime for a given surfactant and conditions. The slopes were also equal to the outlet pressures for the dP curves as a function of qt in tests 2 and 3. Irrespective the linear correlation between dP and ql, the deviations were observed at medium values of foam quality at 400 psi. These deviations were accompanied by the simultaneous deviations in the length of foam drops, showing that they were of nonrandom nature. In some deviating points, the foam texture at the outlet changed abruptly and disproportionately to fg changes. This could be the evidence of the intermediate state between the coarse-foam and strong-foam. • The dP of foam flow is a linear function of liquid flow rate with a line slope equal to the outlet pressure. • Due to the mathematical expression, dP = P · ql can be called the equation of ideal foam. • Deviations from linear function at some points are caused by disproportionate changes in foam texture. • Transition foam quality is higher for foaming agents with higher initial viscosity.

Study on interfacial tension of surfactant and its oil displacement performance

Tuha oil field is located at the Turpan basin in China. Currently, the water content of the main reservoir of the section Y-6 of the Tuha oil field is more than 93% and the recovery rate is less than 20%. At present, an efficient oil displacing agent must be selected for this oil field, which can be used in reservoirs with a high degree of mineralization. Based on the results of experiments measuring the interfacial tension of the surfactant solution and oil, a non-ionic surfactant was selected. Non-ionic surfactant can reduce interfacial tension to the ultra-low level (10−3 mN/m), and when the amount of adsorption by oil sand is 3, interfacial tension also can maintain at the level of 10−2 mN/m, so the solution of non-ionic surfactant has good anti-adsorption ability. The results of the oil displacement experiments show that the solution of a non-ionic surfactant can increase the efficiency of oil displacement. But under condition of high water cut, the dominant flow channel in the core is formed, and the surfactant solution flows into the main channel preferentially and reduces the residual oil saturation in the main channel, which leads to a decrease in the resistance coefficient and injection pressure. Therefore, after water flooding, take measures to control the fluid profiles firstly so that the following surfactant solutions change direction in areas not exposed to water in order to achieve the best effect of the increase in oil recovery.

Asymmetrical Velocity Distribution in the Drag-Reducing Channel Flow of Surfactant Solution Caused by an Injected Ultrathin Water Layer

Although the turbulent intensity is suppressed in the drag-reducing channel flow by viscoelastic additives, the mean velocity distribution in the channel flow is symmetrical and tends to be similar to the laminar flow. In the study of near-wall modulation of the drag-reducing flow with an injected ultrathin water layer, an asymmetrical mean velocity distribution was found. To further investigate this phenomenon and the underlying cause, an experiment was carried out with the water injected from a porous channel wall at a small velocity (~10−4 m/s) into the drag-reducing flow of surfactant solution. The instantaneous concentration and flow fields were measured by using planar laser-induced fluorescence (PLIF) and particle imaging velocimetry (PIV) techniques, respectively. Moreover, analyses on turbulent statistical characteristics and spatial distribution of viscoelastic structures were carried out on the basis of comparison among various flow cases. The results showed that the injected ultrathin water layer under present experimental conditions affected the anisotropy of the drag-reducing flow. The characteristics, such as turbulence intensity, showed the zonal feature in the wall-normal direction. The Reynolds shear stress was enhanced in the near-wall region, and the viscoelastic structure was modified severely due to the redistributed stress. These results may provide experimental supports for the near-wall modulation of turbulence and the exploration of the drag-reducing mechanism by viscoelastic additives.

Viscoelastic surfactant fluids filtration in porous media: A pore‐scale study

AbstractWe investigated the flow of viscoelastic surfactant (VES) solutions, an important type of fracturing fluids for unconventional hydrocarbon recovery, through a diverging–converging microfluidic channel that mimics realistic unit in porous media. Newtonian fluid and viscoelastic hydrolyzed polyacrylamide (HPAM) solution were used as control groups. We vary Deborah numbers (De) up to 61.2, and found that the flow patterns of HPAM and VES solutions become very different once De ≥ 6.12. This is attributed to different generation mechanisms of viscoelasticity, thus different responses to extensional rates at pore‐throats, for HPAM and VES solutions. It results in significantly smaller pressure drop of VES solutions through the microchannel compared to HPAM solution. It interprets higher filtration loss of VES solution than HPAM in core experiments and in field observations. The set‐up can be generalized as a prototype to effectively evaluate the filtration of fracturing fluids.

Experimental study on the characteristics of foam flow in fractures

Foam is widely used in well treatment or enhanced oil recovery (EOR). In EOR, foam is an effective agent for mobility control to improve sweep efficiency. Foam's flow characteristic is the foundation of its application. In this work, we systematically investigated the effects of the surfactant concentration, the liquid flow rate, and the fracture width on the flow resistance and the bubble shape characteristics of foam in a fracture by using a visualized fracture model. The results showed that the pressure drop increased with the concentration of the surfactant. When the concentration of surfactant was 0.03%, the pressure drop reached a maximum value at a foam quality of 60%, and this value increased to 92% for a surfactant concentration of 0.3%. The pressure drop reached a maximum with the surfactant solution flow rate and decreased thereafter, and the pressure drop reached a maximum for a foam quality of 92% at the gas flow velocity of 2.0 m/min. The foam bubbles were small in diameter and high in number with the increase of surfactant concentration. The number of polygonal foam bubbles raised with the foam quality, and the bubble shape shifting took place at a foam quality of 90%. The flow resistance of the foam in the fracture dropped with the fracture width, and the fracture width hardly affected the shape and size of the foam.

An anomalous curved jet emerging from laminar Poiseuille flow (gel-like behavior and breakdown of transparent shear-induced structures in dilute cationic surfactant solutions)

A laminar Poiseuille flow of a dilute cationic surfactant solution produces threadlike shear-induced structures (SISs) that are dispersed densely within a near-wall layer. This near-wall SIS layer behaves like a coherent gel within the jet. When the jet impinges on the wall, it is found to anomalously curve aside from the wall rather than impinging straight. With an increase in the flow rate, this curved jet becomes a straight impinging jet, and the SIS layer is broken down by compression at the wall stagnation point. The normal stress at the stagnation point is investigated as the critical condition for SIS breakdown and is represented as a function of the wall shear stress of the channel flow. The critical normal stress increases with the wall shear stress in the channel flow and then decreases rapidly above the critical wall shear stress. In addition to the gel-like coherent characteristics of the SIS layer, the macroscopic apparent viscosity of the SIS layer is investigated and estimated to be 2.5–5 mPa s in the channel flow. The SIS layer shows a rather low macroscopic apparent viscosity despite its gel-like coherent behavior.

Drag reduction and thermal characteristics to local heating of the channel wall in surfactant solution flow

Drag reduction and thermal characteristics to local heating of the channel wall in surfactant solution flow

Drag reduction and temperature distribution to local heating of the channel wall in surfactant solution flow

Drag reduction and temperature distribution to local heating of the channel wall in surfactant solution flow

Changes in flow structure in the Turbulent Transition of Surfactant Solution Flow

Changes in flow structure in the Turbulent Transition of Surfactant Solution Flow

Drag Reduction Characteristic in Surfactant Solution Flow of Pipe with Curved or Different Diameter

Drag Reduction Characteristic in Surfactant Solution Flow of Pipe with Curved or Different Diameter

Foam Generation by Capillary Snap-Off in Flow Across a Sharp Permeability Transition

Summary Foam reduces gas mobility and can improve sweep efficiency in an enhanced-oil-recovery (EOR) process. Previous studies show that foam can be generated in porous media by exceeding a critical velocity or pressure gradient. This requirement is typically met only near the wellbore, and it is uncertain whether foam can propagate several tens of meters away from wells as the local pressure gradient and superficial velocity decreases. Theoretical studies show that foam can be generated, independent of pressure gradient, during flow across an abrupt increase in permeability. In this study, we validate theoretical predictions through a variety of experimental evidence. Coreflood experiments involving simultaneous injection of gas and surfactant solution at field-like velocities are presented. We use model consolidated porous media made out of sintered glass, with a well-characterized permeability transition in each core. The change in permeability in these artificial cores is analogous to sharp, small-scale heterogeneities, such as laminations and cross laminations. Pressure gradient is measured across several sections of the core to identify foam-generation events and the subsequent propagation of foam. X-ray computed tomography (CT) provides dynamic images of the coreflood with an indication of foam presence through phase saturations. We investigate the effects of the magnitude of permeability contrast on foam generation and mobilization. Experiments demonstrate foam generation during simultaneous flow of gas and surfactant solution across a sharp increase in permeability, at field-like velocities. The experimental observations also validate theoretical predictions of the permeability contrast required for foam generation by “snap-off” to occur at a certain gas fractional flow. Pressure-gradient measurements across different sections of the core indicate the presence or absence of foam and the onset of foam generation at the permeability change. There is no foam present in the system before generation at the boundary. CT measurements help visualize foam generation and propagation in terms of a region of high gas saturation developing at the permeability transition and moving downstream. If coarse foam is formed upstream, then it is transformed into stronger foam at the transition. Significant fluctuations are observed in the pressure gradient across the permeability transition, suggesting intermittent plugging and mobilization of flow there. This is the first CT-assisted experimental study of foam generation by snap-off only, at a sharp permeability increase in a consolidated medium. The results of experiments reported in this paper have important consequences for a foam application in highly heterogeneous or layered formations. Not including the effect of heterogeneities on gas mobility reduction in the presence of surfactant could underestimate the efficiency of the displacement process.

Exergy transfer characteristics analysis of turbulent heat transfer enhancement in surfactant solution

This paper presents an exergy transfer analysis for turbulent drag reducing surfactant solution flow with and without heat transfer enhancement devices which employ static or dynamic mixers. Heat transfer and pressure drop measurements were performed at an inlet temperature of 297.7–298.2 K in pipe flow with a concentric tube heat exchanger. The environmental temperature in the analysis was set to be 288.2 K in assumption of a cooling system. The experimental range of the Reynolds number was 1.0×104 to 4.2×104. Adding surfactant to a water flow decreases the exergy transfer Nusselt number, Nue, owing to the heat transfer reduction and increases the exergy transfer efficiency, ηeff, by a maximum of 9.3% at high Reynolds numbers at moderate fluid transport distance owing to the drag reduction. Also the secondary flow caused by the enhancement devices increases Nue. The proposed flow performance curve which provides ηeff for an arbitrary Nue shows that ηeff in viscoelastic fluid flow compared to Newtonian fluid flow is small independently of the fluid transport distance, and that the installation of heat transfer enhancement devices has a positive effect on energy-saving in certain ranges of Reynolds numbers and fluid transport distances.

Foam propagation and oil recovery potential at large distances from an injection well

While foam propagation, foam–oil interaction and foam oil recovery performance have been investigated by numerous research studies, most of previous works were performed on short porous media with the maximum length of 30cm. Therefore, their results mostly represent foam behavior in the vicinity of the injection well and may not represent the foam propagation, quality and oil recovery potential at large distances from the injection well. In this study, by using a high-pressure and high-temperature rig equipped with a 12-m long porous medium and microscopic visualization facilities, foam stability in the presence and absence of a reservoir crude oil, foam propagation, foam–oil interaction, and finally foam oil recovery potential at large distances from the injection well were investigated. The oil recovery behavior of four tertiary scenarios, including Sodium Dodecyl Sulfate (SDS) foam, Alpha-Olefin Sulfonate (AOS) foam, gas, and simultaneous water alternating gas (SWAG) injection, were investigated.According to results, pressure presented a positive impact on the foam stability. The extent of this impact was a function of the surfactant type. Compared to gas and SWAG injection, in the 12-m long porous medium, foam flooding scenarios presented much stronger oil recovery potentials. This reveals the strong potential of foam flooding in producing the oil trapped in areas deep into the reservoir and far from the injection well. Based on this study, by using a suitable surfactant solution and optimum gas fractional flow, even in the presence of oil, foam can propagate to large distances from the injection well and leads to extra oil recovery.

Direct numerical simulation of surfactant solution flow in the wide‐rib rectangular grooved channel

The turbulent flow of surfactant solution in the wide‐rib rectangular grooved channels was studied by direct numerical simulation. Moreover, the variations of near‐wall streamwise vortices with time were discussed and the distributions of streamwise vortex radius, swirling strength and density were quantitatively investigated. It was found that the influence of microgrooves on the fluid mainly occurred within the buffer layer and microgrooves could induce numerous streamwise vortices with small size and swirling strength within the grooved valleys. The drag‐reducing enhancement mechanism of microgroove in the surfactant solution could be mainly considered as the competing results between the “restriction effect” and “tip effect” of microgroove, and the essential factor should be the numerous secondary streamwise vortices with small size and swirling strength within the grooved valleys. Furthermore, a predicted method for the optimal drag‐reducing size of microgroove was proposed, and the prediction values agreed well with the numerical results. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2898–2912, 2018

Simultaneous determination of micellar structure and drag reduction in a surfactant solution flow using the fluorescence probe method

As widely known, the addition of a specific type of surfactant to water reduces drag in a pipe flow. This effect is considered to be a result of the suppression of turbulent transition caused by the ordered structure of rod-like micelles that is referred to as a shear-induced structure (SIS). However, it is typically difficult to determine the SIS since it is necessary to noninvasively detect the SIS with several hundred nanometers in the actual moving flow. In this study, we used the fluorescence probe method to locally determine the SIS in a pipe flow. When hydrophobic fluorescence molecules are added to the surfactant solution, the fluorescence molecules are trapped in micelles. Thus, fluorescence intensity varies based on the change in the micellar structure. We verified the applicability of the fluorescence probe method to the SIS detection and determined the relationship between the micellar structure and the drag reduction in the pipe flow by simultaneously measuring the fluorescence intensity and pipe friction factor. The experimental result demonstrates that the SIS formation in the near-wall region is closely correlated with the drag reduction and suggests that the near-wall SIS suppresses the turbulent transition.

Drag Reduction Characteristic in Surfactant Solution Flow of Pipe with Curved or Different Diameter

Drag Reduction Characteristic in Surfactant Solution Flow of Pipe with Curved or Different Diameter

Changes in higher order micellar structures in the Turbulent Transition of Surfactant Solution Flow

Changes in higher order micellar structures in the Turbulent Transition of Surfactant Solution Flow