Foam Coalescence Research Articles

Effect of Newtonian and non-Newtonian viscosifying agents on stability of foams in enhanced oil recovery. Part I: under bulk condition

Foams show poor stability in enhanced oil recovery applications and stimulation processes in oil-well operations of oil fields. This paper presents a laboratory study to investigate the effect of Newtonian and non-Newtonian viscosity enhancement materials on improving the stability of foams at bulk conditions. For this goal, glycerol and hydrolyzed polyacrylamide (HPAM) were utilized to enhance the viscosity of foaming agents, which were composed of α-olefin sulfonate surfactant and salinity. To this end, a comparative study of the foam stability in surfactant solution containing different percentages of glycerol, HPAM polymer and a mixture of polymer with glycerol was undertaken. In a foam stability analysis, which was examined in the absence of an oleic phase, several characteristics such as foam volume evolution, foam half-decay time and a liquid fraction of foam were measured over a wide range of concentrations. Evaluating the conductivity and volume of injected gas during foam generation and foam decay provided the foam capacity and the maximum density parameters to characterize the foamability and stability of the generated foam in more detail. The results of bulk foam experiments indicated that polymer and glycerol could either increase or reduce the foamability, but both materials substantially increased foam stability within a certain range of concentrations. This could be explained by increasing the viscosity of the liquid phase of foam in the lamellae that attributed to decreased velocity of liquid drainage from the foam structure. Two regimes of foam drainage and coalescence demonstrated a different behavior for the same viscosity of solutions containing either glycerol or HPAM polymer. The solutions containing glycerol exhibited a small but sharp decay right after stopping the sparging gas, while for high polymer concentrations this did not happen.

Coalescence in Two-Dimensional Foams: A Purely Statistical Process Dependent on Film Area.

While coalescence is ultimately the most drastic destabilization process in foams, its underlying processes are still unclear. To better understand them, we track individual coalescence events in two-dimensional foams at controlled capillary pressure. We obtain statistical information revealing the influence of the different parameters which have been previously proposed to explain coalescence. Our main conclusion is that coalescence probability is simply proportional to the area of the thin film separating two bubbles, suggesting that coalescence is mostly stochastic.

Chitin Nanofibrils to Stabilize Long-Life Pickering Foams and Their Application for Lightweight Porous Materials

The demand of sustainable development is challenging researchers to convert renewable resourced biomass into functional materials via environmentally friendly and sustainable pathways. This work introduces a long-life Pickering foam stabilized by chitin nanofibers (CNFs) as colloidal rod-like particles, and a facile method for fabricating lightweight porous solid foams that recycles biomass materials derived from seafood waste. These foams were formed by combining nonionic surfactant Tween 20 (T20) and CNFs, with the CNFs being irreversibly adsorbed at the air–water interface to provide Pickering stabilization. At a concentration of 7.5 mg/mL, the foams could be stable for over 1 week without any apparent drainage. The rheological data indicated the formation of gel networks by self-aggregated CNFs at the air–water interface, which provided long-term stabilization by preventing foam coalescence and disproportionation. This long-term stability of CNF-T20 wet foam has permitted the fabrication of solid poro...

Methodology for the Development of Laboratory–Based Comprehensive Foam Model for Use in the Reservoir Simulation of Enhanced Oil Recovery

Summary An integrated methodology is presented for the development of a comprehensive empirical foam model based on tailored laboratory tests and representative numerical simulations that encompass processes of foam generation, coalescence, and shear thinning along with rheological characteristics and associated flow regimes. Steady-state and unsteady-state laboratory experiments of foam floods in a vertical column of sandpack with and without oil at different surfactant concentrations and at varied gas/surfactant-solution injection rates are designed, conducted, and analyzed. The logic and basis of these experiments are provided. Test results from experiments in the presence of oil provide information on the oil-induced foam/lamella coalescence functions. Unsteady-state experiments capture foam-generation and foam-dry-out phenomena, whereas steady-state experiments capture the effects of foam quality, foam velocity, and surfactant concentration. Process-based numerical simulations of these experiments are combined with basic governing analytical relationships of foam flow to provide a methodology for a comprehensive empirical foam model and to uniquely define the model parameters to preserve consistency with simulations of foam-flow processes. A procedure is presented to fully model the effect of surfactant concentration on foam strength and to quantify all concentration-function parameters, and, in particular, epsurf.

Modeling foam flow at achievable flow rates in the subterranean formation using the population-balance approach and implications for experimental design

A correct understanding of foam generation, coalescence and transport at achievable reservoir flow rates has been a key issue for its applications in enhanced oil recovery processes. Use of foam models to simulate foam flow in the reservoir requires establishing of the parameters in the lab. This is generally done at relatively high flow rates in a so-called strong-foam state, which covers both high- and low-quality foam regimes that are used to fit foam modeling parameters. In the reservoir, because of the in situ velocities changing between near and far from the wellbore, there is a need for the foam model to be able to predict the foam behavior at two different foam states with high and low velocities, respectively. Depending upon the petrophysical properties of the reservoir, one may not generate and transport strong foam at the low-velocities away from the well.Bubble population-balance models are considered a useful tool to understand foam flow through porous media by addressing the phenomenon from the first principle of physics. We investigated the capability of available population-balance models to simulate these two foam states over a wide range of velocities. Using an example case, the same set of data was fit to two well-known models at relatively high flow rates. Both models fit the steady-state data at high-flow rates reasonably well through proper tuning of the parameters. One foam model, reported by Afsharpoor and co-workers in 2010, predicted a weak-foam state with much lower apparent viscosity at low flow rates; however, the other model, reported by Chen and co-workers in 2010, predicted much higher pressure gradient at low flow rates with the same set of relative permeability and capillary pressure curves, due to the shear-thinning effect and the foam generation effect in the absence of a minimum pressure gradient (MPG). We observed significantly different foam rheology above the MPG: shear-thinning behavior when the foam texture reaches the maximum and Newtonian behavior when the foam texture is below the maximum. Below the MPG, a shear-thickening behavior, with an abrupt change at the boundary, was predicted by Afsharpoor model as was earlier observed in several experiments reported in the literature. The sensitivity of MPG to the corresponding critical velocity in Afsharpoor model is also studied in this work.The data acquired in steady-state experiments have to be in the strong-foam state in order to estimate correct parameters in the model to simulate foam behavior in high- and low-quality regimes. However, if the experimental data acquired at low fluid velocities is available and indicates a weak-foam state at low velocities, one can use Afsharpoor model to predict this weak-foam state away from the well. Note that the findings are limited to steady-state foam flows in relatively homogeneous systems, while transient foam modeling and the impact of heterogeneity / pore-network distribution are yet to be investigated.

Mechanistic study of nanoparticles–surfactant foam flow in etched glass micro-models

ABSTRACTThis study was conducted in order to identify the pore-level mechanisms controlling the nanoparticles–surfactant foams flow process and residual oil mobilization in etched glass micro-models. The dominant mechanism of foam propagation and residual oil mobilization in water-wet system was identified as lamellae division and emulsification of oil, respectively. There was inter-bubble trapping of oil and water, lamellae detaching and collapsing of SDS-foam in the presence of oil in water-wet system and in oil-wet system. The dominant mechanisms of nanoparticles–surfactant foam flow and residual oil mobilization in oil-wet system were the generation of pore spanning continuous gas foam. The identified mechanisms were independent of pore geometry. The SiO2-SDS and Al2O3-SDS foams propagate successfully in water-wet and oil-wet systems; foam coalescence was prevented during film stretching due to the adsorption and accumulation of the nanoparticles at the gas–liquid interface of the foam, which increased the films’ interfacial viscoelasticity.

Effect of permeability on foam-model parameters: An integrated approach from core-flood experiments through to foam diversion calculations

We present a set of steady-state foam-flood experimental data for four sandstones with different permeabilities, ranging between 6 and 1900 mD, and with similar porosity. We derive permeability-dependent foam parameters with two modelling approaches, those of Boeije and Rossen (2015a) and a non-linear least-square minimization approach (Eftekhari et al., 2015). The two approaches can yield significantly different foam parameters. Thus, we critically assess their ability in deriving reliable foam parameter estimates. In particular, the way the two approaches treat shear-thinning foam behaviour and foam coalescence is discussed. The foam parameter set acquired from the latter approach is further used as input in foam diversion calculations: this serves to evaluate mobility predictions in non-communicating reservoir layers. This study aims to provide a framework to integrate experimental work, modelling and simple qualitative diversion calculations to provide a background for the upscaling of foam studies, with particular focus on heterogeneous systems.

Modeling fracture propagation and cleanup for dry nanoparticle-stabilized-foam fracturing fluids

Nanoparticle (NP)-stabilized foams can be generated at extreme water-deficient conditions (with quality as high as 95–99%) and yet with apparent viscosities >100cP. This makes them greatly appealing for hydraulic fracturing applications, where minimal water consumption and leak-off to the reservoir are desired. Initial assessment of propensities of these novel fluids for fracturing applications requires field scale simulations. However, conventional fracturing models are difficult to employ because they do not consider true foam hydrodynamics. We have developed a mathematical model to simulate the transport of NP-stabilized foams for hydraulic fracturing. The model combines fluid transport in reservoir matrix and fracture with rock mechanics equations and thus allows for considering the effects of foam on fracture dynamics. Gas and water flow with mechanistic accounting of foam generation and coalescence are simulated using population balance models. Transport of nanoparticles through porous media was simulated using single site filtration model. The equations are discretized using finite-difference scheme. Settari’s approach is used to embed fracture’s moving boundary with the matrix to accordingly update transmissibility. Model’s capabilities are verified with examples on fracture growth and fracture clean up processes to illustrate the benefits of using the NP-stabilized high quality foams. Fracture propagation was simulated for water, a conventional viscous fracpad and NP-stabilized foams of different qualities and textures. The simulations confirmed that larger foam viscosity generated wider fractures with smaller fracture half-length. In addition, fracture cleanup simulations show that fracturing fluid cleanup for foam based fracturing fluids could take the order of 10 days as opposed to that of viscous fracpad which could take up to 1000 days; demonstrating the advantage of using dry foams.

The Investigation of Rheological Properties Development for Polymer Matrix Including Foaming Agent

Sole in the footwear usually modified with foaming agent on the polymer resin to improve the lightweightness and crush-cushion effect. In this study, we investigated rheological properties for polymer resin filled with the different type and concentration of foaming agent, capsule type foaming agent and organo-chemical foaming agent, under the time sweep test. Curing times of each polymer resin with different kind of foaming agent are delayed than reference material (epoxy resin with curing agent). In case of adding capsule type foaming agent, however, there is appropriate concentration to reduce the curing time, relatively. When foaming agent is activated, foaming force inflates the sample in contrast to condensation force of curing and then axial normal force develop to the (+) direction. Interestingly, by increase concentration of foaming agent, there is a specific point to break down the axial normal force development. The reason for this phenomenon is that coalescence of foams induce the blocking of axial normal force development.

Viscosity and stability of ultra-high internal phase CO2-in-water foams stabilized with surfactants and nanoparticles with or without polyelectrolytes

To date, relatively few examples of ultra-high internal phase supercritical CO2-in-water foams (also referred to as macroemulsions) have been observed, despite interest in applications including “waterless” hydraulic fracturing in energy production. The viscosities and stabilities of foams up to 0.98 CO2 volume fraction were investigated in terms of foam bubble size, interfacial tension, and bulk and surface viscosity. The foams were stabilized with laurylamidopropyl betaine (LAPB) surfactant and silica nanoparticles (NPs), with and without partially hydrolyzed polyacrylamide (HPAM). For foams stabilized with mixture of LAPB and NPs, fine ∼70μm bubbles and high viscosities on the order of 100 cP at>0.90 internal phase fraction were stabilized for hours to days. The surfactant reduces interfacial tension, and thus facilitates bubble generation and decreases the capillary pressure to reduce the drainage rate of the lamella. The LAPB, which is in the cationic protonated form, also attracts anionic NPs (and anionic HPAM in systems containing polymer) to the interface. The adsorbed NPs at the interface are shown to slow down Ostwald ripening (with or without polymer added) and increase foam stability. In systems with added HPAM, the increase in the bulk and surface viscosity of the aqueous phase further decreases the lamella drainage rate and inhibits coalescence of foams. Thus, the added polymer increases the foam viscosity by threefold. Scaling law analysis shows the viscosity of 0.90 volume fraction foams is inversely proportional to the bubble size.

Effect of Permeability on Implicit-Texture Foam Model Parameters and the Limiting Capillary Pressure

Accurate modeling of foam rheology on the field scale requires detailed understanding of the correlation between the fundamental properties of foam and the scalable parameters of the porous medium. It has been experimentally observed that foam experiences an abrupt coalescence when the capillary pressure in the porous medium approaches a certain value referred to as the “limiting capillary pressure”, Pc*. Current foam models that treat foam texture implicitly mimic this fundamental behavior with a so-called dry-out function, which contains adjustable parameters like fmdry and epdry (in the STARS foam simulator). Parameter fmdry (called Sw* in other models) represents the water saturation corresponding to the limiting capillary pressure, Pc*, and epdry determines the abruptness of foam coalescence as a function of water saturation. In this paper, using experimental data, we examine the permeability dependence of these parameters. We find that the value of fmdry decreases with increasing permeability. We also find that, for the data examined in this paper, the transition from the high-quality regime to low-quality regime is more abrupt in lower-permeability rocks. This implies that in high-permeability rocks foam might not collapse abruptly at a single water saturation; instead, there is a range of water saturation over which foam weakens. In addition, we address the question of whether Pc* is dependent on formation permeability. We estimate Pc* from data for foam mobility versus foam quality and find, as did Khatib et al. (SPE Reservoir Eng., 1988, 3 (3), 919–926), who introduced the limiting capillary pressure concept, that Pc* can vary with permeability. It increases as permeability decreases, but not enough to reverse the trend of increasing foam apparent viscosity as permeability increases.

CO2 foam flooding for improved oil recovery: Reservoir simulation models and influencing factors

A mechanistic model of CO2 foam that allows for direct simulation of foam generation, propagation, coalescence and collapse was described in this study. The controlling parameters, such as reaction rate factors for foam generation, coalescence and collapse in presence of oil, the viscosity of foaming components and surfactant adsorption, were adjusted to match the experimental results of CO2 foam coreflooding. A three dimensional heterogeneous conceptual reservoir model was then built to study the mechanisms of CO2 foam flooding based the foam model. The simulation results show that CO2 foam flooding can improve oil recovery through a combination of various mechanisms, including selective blocking and conformance control, gas up-flow effect, reservoir energy support, and the improvement of displacement efficiency. The sensitivity and the effect of different influencing factors on the performance of CO2 foam flooding were investigated via the simulation models on various scenarios. CO2 foam flooding can achieve a better oil recovery in comparison with water flooding, CO2 flooding and WAG (water alternating gas) processes. Early CO2 foam injection is conducive to the improvement of oil recovery and the success of the project. CO2 foam flooding technique can be applied in a wide range of complex reservoirs, especially for highly heterogeneous reservoirs with high permeability channels, and reservoirs with different sedimentary sequences.

Numerical Calculation of Transient Flow of Polymer Foam in Porous Media

Based on the mathematical model of one dimension transient flow of the polymer foam in porous media, the numerical calculation method of the flow mentioned above by using the finite difference method is given. Through the experiments of one dimension transient flow of HPAM (Hydrolytic Polyacrylamide) foam in the artificial sandstone core, the HPAM foam generation and coalescence coefficient of the mathematical model mentioned above are determined. The profiles of the liquid phase saturation, the pressure drop and the number density of one dimension transient flow of HPAM foam with the dimensionless time in artificial sandstone core are numerically calculated and analyzed by using the numerical calculation method.

Thermodynamic and Mechanical Timescales Involved in Foam Film Rupture and Liquid Foam Coalescence

Recent advances in the coalescence in liquid foams are reviewed, with a special focus on the multiscale structure of foams. Studies concerning the stability of isolated foam films, on the one hand, and the coalescence process in macroscopic foams, on the other hand, are not always in good agreement. This discrepancy reveals that two routes can induce coalescence in a foam. The first route is thermodynamic and shows that coalescence is governed by a stochastic rupture of foam films. The second route relies on a mechanically induced rupture of the films, due to the spontaneous evolution of foams. From a literature review, the evaluation of the different timescales involved in these mechanisms allows defining the limiting parameters of foam coalescence.

Coalescence of dry foam under water injection.

When a small volume of pure water - typically a drop - is injected within an aqueous foam, it locally triggers the rupture of foam films, thus opening an empty cavity in the foam's bulk. We consider the final shape of this cavity and we quantify its volume as a function of the volume of injected water, the diameter of the bubbles and the liquid fraction of the foam. We provide quantitative understanding to explain how and when this cavity appears. We epitomize the dilution of surfactants at the water-air interfaces as the main cause lying behind the coalescence process. We identify a new coalescence regime for which a critical surfactant concentration rules the stability of the foam.

Self-similar coalescence of clean foams

AbstractWe consider the stability of a planar gas–liquid foam with low liquid fraction, in the absence of surfactants and stabilizing particles. We adopt a network modelling approach introduced by Stewart & Davis (J. Rheol., vol. 56, 2012, p. 543), treating the gas bubbles as polygons, the accumulation of liquid at the bubble vertices (Plateau borders) as dynamic nodes and the liquid bridges separating the bubbles as uniformly thinning free films; these films can rupture due to van der Waals intermolecular attractions. The system is initialized as a periodic array of equally pressurized bubbles, with the initial film thicknesses sampled from a normal distribution. After an initial transient, the first film rupture initiates a phase of dynamic rearrangement where the bubbles rapidly coalesce, evolving toward a new quasi-equilibrium. We present Monte Carlo simulations of this coalescence process, examining the time intervals over which large-scale rearrangement occurs as a function of the model parameters. In addition, we show that when this time interval is rescaled appropriately, the evolution of the normalized number of bubbles is approximately self-similar.

Modeling foam displacement in fractures

The use of the population-balance approach is extended to include the description of foam transport in fractures. We study numerically foam flow resistance as a function of gas and liquid velocities and the degree of fracture heterogeneity. The mechanisms of foam flow resistance, generation, and coalescence are similar among fractured and unfractured media but the macroscopic expression of non-linear foam physics is different. The possibility of continuously varying gas–liquid curvature in response to capillary pressure and the relationship of curvature to foam apparent viscosity, however, results in different pressure drop behavior in fractures as gas flow rate and foam quality are varied. The full physics foam model is modified to incorporate this relationship in the simulations. The foam flow resistance parameter is then calculated locally. The simulated fracture models include one- and two-dimensional heterogeneous and a radial homogeneous model. Model predictions compare favorably to experimental literature data.

Free drainage of aqueous foams stabilized by mixtures of a non-ionic (C12DMPO) and an ionic (C12TAB) surfactant

The study at hand investigates the influence of the composition of a surfactant mixture on the free drainage of the respective foams. The Foam Conductivity Apparatus (FCA) was used to study free drainage of foams of homogeneous initial liquid fraction εinit. The foams were stabilized with mixtures of the non-ionic surfactant dodecyldimethyl phosphineoxide (C12DMPO) and the cationic surfactant dodecyl trimethylammonium bromide (C12TAB) at mixing ratios of C12DMPO:C12TAB=1:0, 50:1, 1:1, 1:50 and 0:1. In all cases the liquid fraction ε follows a power law with respect to time t, i.e.ε ∼tη with −1.0<η<−0.8. The η-values are all very similar which indicates a Poiseuille-like flow (−1<η<−2/3) for all samples irrespective of changes in composition and bubble size. For all studied mixtures drainage led to fairly dry foams (ε ∼ 10−3), which then either coalesce (C12DMPO and 50:1 mixture) or drain further (1:1 mixture). An evaluation of the critical liquid fraction εcrit (liquid fraction at which foam coalescence sets in abruptly) revealed that εcrit is independent of the foam height and the bubble size which is in line with literature. However, it depends on the composition of the surfactant mixture and decreases with increasing content of C12TAB.

Geophysical Monitoring of Foam Used to Deliver Remediation Treatments within the Vadose Zone

Foam is a promising vehicle for delivering amendments into the vadose zone for in situ remediation; it is an approach being considered for in situ treatment and stabilization of metals and radionuclides located within the deep vadose zone of the Department of Energy's Hanford Site in the state of Washington. A central aspect of evaluating the effectiveness of this approach is the ability to monitor foam distribution, its transformation, and the reactions that it induces in the subsurface, ideally in a noninvasive manner. In this study, we performed laboratory experiments to evaluate the potential of geophysical methods (complex resistivity and time‐domain reflectometry [TDR]) as tools for monitoring foam‐assisted amendment delivery in the deep vadose zone. Our results indicated great sensitivity of electrical methods to foam transportation and evolution in unsaturated porous media that were related to foam bubble coalescence and drainage processes. Specifically, we observed (i) a decrease in electrical resistivity (increase in electrical conductivity) by more than an order of magnitude in both silica sand and natural sediment matrices during foam transportation; (ii) an increase in resistivity (decrease in conductivity) of more than twofold during foam coalescence and drainage; and (iii) a distinct phase and imaginary conductivity signature related to the evolution of water films on sediment grains during foam injection and evolution processes. To assist with the interpretation of these data, TDR measurements were used to monitor moisture content, which provided complementary information about foam distribution and drainage. Our results clearly demonstrated the sensitivity of electrical and TDR signals to foam transportation and evolution in unsaturated porous media and suggest the potential of these methods for monitoring the response of a system to foam‐based remediation treatments at field scales.

Roles of transient and local equilibrium foam behavior in porous media: Traveling wave

In foam EOR, complex dynamics of bubble creation and destruction controls foam properties. Recently, there has been consensus that local equilibrium between bubble creation and destruction adequately describes foam displacements. We assume that local equilibrium applies throughout a foam displacement on the field scale, with the exception of an entrance region and at shock fronts, where saturations and texture (bubble size) change abruptly. We find a range of conditions in which the local-equilibrium condition applies even within the shock front. In a waterflood, the width of a shock transition zone is determined by capillary-pressure gradients. For foam, this equation is joined by one for evolving foam texture. One expects that slow foam dynamics widens the traveling wave at the shock considerably. Theory and simulations show that the width of and mobility inside a shock front can affect foam sweep. If there is no gas ahead of the foam, as is common in published simulations, we prove that foam texture is everywhere at local equilibrium within the shock, regardless of the foam model, as previously observed for one dynamic foam model. If there is gas initially in the formation, slow foam generation and coalescence processes can actually narrow the shock from that assuming local equilibrium. In other cases, the dynamics of the traveling wave leads to oscillations near the shock; these are not numerical artifacts, but reflections of the models. Multiple steady states seen in experiment for some injection rates can be predicted by certain foam models. The approach of solving for the traveling wave can rule out some of these states for certain displacements.