Surfactants In Porous Media Research Articles

A study on the emulsification ability and oil displacement efficiency of polymeric surfactant in porous media

In order to comprehensively comprehend the distinctions in solution properties, emulsification characteristics, and oil displacement efficiency between polymeric surfactant(DG-1) and traditional polymers or surfactants, a comparative analysis was initially conducted on the microstructure, main functional group types, and macroscopic properties. Subsequently, core displacement experiments were employed to elucidate the emulsification capability, emulsion stability, and oil displacement properties of polymeric surfactants. The microscopic displacement experiment was ultimately conducted to investigate the residual oil displacement process in the core following polymer displacement by DG-1, thereby elucidating the underlying mechanisms of microscopic oil displacement by DG-1. The results indicate DG-1 has a molecular structure with a regional network aggregation state as a whole, and a multi-layer aggregation and overlapping structure in space. DG-1exhibits higher viscosity and lower interfacial tension due to the larger molecular coil dimension compared to the equivalent concentration of polymers. The emulsification ability of DG-1 is robust, with emulsion stability positively correlated to oil-polymer ratio and concentration while negatively correlated to migration distance. Core displacement experiments results indicate the polymer-surfactant system (SP) and DG-1 exhibited comparable oil displacement effects, with oil recovery of 54.5 % and 52.4 %, respectively, both surpassing the recovery achieved by the polymer alone (46.9 %). In heterogeneous reservoirs, SP acts as the dominant displacer in regions with moderate and high permeability, whereas DG-1 assumes dominance in regions with moderate and low permeability. The microscopic displacement experiments revealed that DG-1 activated the clustered residual oil as the predominant type of residual oil in porous media, followed by columnar and block residual oil, with film residual oil exhibiting the least activation. Primary mechanisms for oil displacement include extended sweeping volume, shear and carrying effects on the residual oil, and eddy displacement of the residual oil by the emulsion.

Research on the Adsorption Law of HFAD Agents on the Surface of Porous Media during Hydraulic Fracturing-Assisted Oil Displacement in Low-Permeability Reservoirs.

Adsorption loss of surfactants in porous media is one of the key factors affecting their application in low-permeability reservoirs. The hydraulic fracturing-assisted oil displacement (HFAD) technology can effectively reduce the adsorption loss of surfactants in porous media. However, the adsorption laws of HFAD agents (surfactants) during the HFAD process are still unclear. It was studied based on physical simulation experiments in this paper. The results showed that 0.3% SY-D as the HAFD agent achieved the best effect, which could reduce the oil-water interfacial tension to 0.0239 mN/m and increase the wettability index to 0.7492. In the high-pressure injection process of HFAD technology, the injection pressure and core permeability are positively correlated with the dynamic saturation adsorption capacity of the HFAD agent on the surface of porous media and the ambient temperature is negatively correlated with it. The higher the injection pressure and the larger the core permeability, the lower the dynamic saturation adsorption capacity of the HFAD agent on the porous media surface. In addition, since adsorption is an exothermic process, increasing the temperature has an inhibitory effect on adsorption. The higher the temperature, the slower the adsorption process of the HFAD agent on porous media. Among the three influencing factors, permeability has the greatest influence on the dynamic saturation adsorption capacity of the HFAD agent on the surface of core porous media, followed by injection pressure, and temperature has the least influence on it. Therefore, when implementing HFAD technology for the reservoir with low permeability, it can be considered to increase the injection pressure of HFAD technology to reduce the dynamic saturation adsorption capacity so as to increase the effective concentration of the agent. The research results have certain guiding significance for the application of HFAD technology in the field.

Influence of Henna Extracts on Static and Dynamic Adsorption of Sodium Dodecyl Sulfate and Residual Oil Recovery from Quartz Sand.

The application of surfactant flooding for enhanced oil recovery (EOR) promotes hydrocarbon recovery through reduction of oil-water interfacial tension and alteration of oil-wet rock wettability into the water-wet state. Unfortunately, surfactant depletion in porous media, due to surfactant molecule adsorption and retention, adversely affects oil recovery, thus increasing the cost of the surfactant flooding process. Chemical-based materials are normally used as inhibitors or sacrificial agents to minimize surfactant adsorption, but they are quite expensive and not environmentally friendly. Plant-based materials (henna extracts) are far more sustainable because they are obtained from natural sources. However, there is limited research on the application of henna extracts as inhibitors to reduce dynamic adsorption of the surfactant in porous media and improve oil recovery from such media. Thus, henna extracts were introduced as an eco-friendly and low-cost sacrificial agent for minimizing the static and dynamic adsorption of sodium dodecyl sulfate (SDS) onto quartz sand in this study. Results showed that the extent of surfactant adsorption was inversely proportional to the henna extract concentration, and the adsorption of the henna extract onto the quartz surface was a multilayer adsorption that followed the Freundlich isotherm model. Precisely, the henna extract adsorption on quartz sand is in the range of 3.12-4.48 mg/g (for static adsorption) and 5.49-6.73 mg/g (for dynamic adsorption), whereas the SDS adsorption on quartz sand was obtained as 2.11 and 4.79 mg/g at static and dynamic conditions, respectively. In the presence of 8000 mg/L henna extract, SDS static and dynamic adsorption was significantly reduced by 64 and 82%, respectively. At the same conditions, the residual oil recovery increased by 9.2% over normal surfactant flooding. The study suggests that the use of henna extracts as a sacrificial agent during SDS flooding could result in the reduction of static and dynamic adsorption of surfactant molecules on quartz sand, thus promoting hydrocarbon recovery from sandstone formations.

Solubilization of residual dodecane by surfactants in porous media: The relation between surfactant partition and solubilization

One-dimensional flow column experiments are conducted to specifically compare the transport behavior of three surfactants (sodium dodecyl benzene sulfonate (SDBS), Triton X-100, rhamnolipid) and a solvent n-propanol and their solubilization on dodecane in porous media. Compared to pentafluorobenzoic acid (PFBA), the low adsorption or partition loss of n-propanol incurred no retardation, shouldering or retention in breakthrough curves. While for surfactants, all the breakthrough curves exhibited retardation, shouldering or retention to different degrees in the presence of dodecane phase. Compared to the anionic SDBS with no significant bulk partition to non-aqueous phase liquid (NAPL), the non-ionic Triton X-100 with partition induced significant retardation and shouldering in breakthrough curves. The retention loss of solubilized aggregates resulted in obvious retention of rhamnolipid at different pore-water velocities. The increase of pore-water velocity could promote the transport of surfactants and the dodecane-surfactant aggregates. The elution of dodecane in the presence of surfactants showed a significant relation to the partition behaviors of surfactants and a characteristic of the rate-limited solubilization. In contrast, the n-propanol, which is basically a non-reactive solvent, exhibited the rapid equilibrium dissolution of dodecane. The results indicated that in remediation of field sites contaminated by hydrophobic organic contaminants (HOCs), the surfactants should be rationally selected, and a favorable pore-water velocity should be used to obtain a high remediation efficiency and to reduce the retention loss of surfactants as well.

Coarsening reduction strategies to stabilize CO2-foam formed with a zwitterionic surfactant in porous media

Micromodel experiments at high-pressure high-temperature conditions were performed to evaluate the impact of different coarsening reduction strategies on CO2-foams stabilized with a zwitterionic surfactant, using silica nanoparticles in small concentration and mixing CO2 with a less water-soluble gas (nitrogen). The CO2-foam stabilized only by the surfactant showed poor behavior in the porous media, while an improvement in both foam texture (bubble density at the inlet of the micromodel) and gas trapping was qualitatively seen in the experiments using a nanofluid containing silica nanoparticles. The strong adsorption of the nanoparticles at the gas-water interface allowed to reduce the coarsening mechanism, reaching a minimum pressure gradient for strong foam generation throughout the micromodel chip. The use of a small concentration of nanoparticles in combination with the zwitterionic surfactant proved to be effective in reducing gas mobility without significant increase in pressure drop, which could be used as a strategy to control the mobility of injected CO2 in high permeability porous media, with reduced loss of injectivity. Coarsening was also reduced by using a mixture of CO2 and N2 as foaming gas, with an even greater gas mobility reduction, achieving a pressure drop 7.6 times higher compared to the CO2-foam stabilized only by surfactant. Furthermore, larger areas with trapped gas were visualized along the micromodel when co-injecting the mixture of gases and the zwitterionic surfactant solution. The large decrease in gas mobility seen for this strategy suggests that using a gas mixture would be suitable to control gas mobility in high-permeability channels and to block thief zones. The combination of using a gas mixture and a nanofluid to decrease CO2-foam destruction in porous media yielded a slight reduction in gas mobility, similar to that obtained with CO2-foam in the presence of nanoparticles, for they had similar pressure-drop values at same injection flow rate. The results obtained in this work demonstrated the importance of interfacial phenomena for tuning of coarsening and coalescence mechanisms associated with CO2-foam stability to the desired pore-scale application.

Pore-Scale Modeling of Two-Phase Flows with Soluble Surfactants in Porous Media

Pore-Scale Modeling of Two-Phase Flows with Soluble Surfactants in Porous Media

Modelization of surfactant flooding: Methodology for determining the interfacial tension function of surfactant concentration and salinity

To predict accurately the amount of oil that can be recovered by a process of surfactant flood injection, a fine modelization of variation of interfacial tension between oil phase and aqueous phase with the reservoir conditions is required. Unfortunately, data of interfacial tension variation with all the parameters, i.e. temperature, salinity and surfactant concentration, are not always available when numerical simulation of the reservoir production is performed. In that case, interpolation is often used, but then cannot be fully representative of the variations. The work presented here details a new numerical model used to describe interfacial tension with all the parameters listed below. This model fit well experimental data obtained for this study. The asymmetry of the model allows to take into account the specificity of industrial formulations, when the interfacial tension at large salinities is different from interfacial tension at zero salinity. The protocol to determine experimental data of optimal salinity and interfacial tensions for such industrial formulations is detailed. The correlation described in this paper is also used to perform numerical experiments of injection of a formulation containing surfactant in porous media to recover oil. The 1D experiments are constructed using realistic parameters from literature. Sensitivity to optimal salinity is described using the interfacial tension model developed here, as well as its impact on oil production.

Experimental investigation on transport property and emulsification mechanism of polymeric surfactants in porous media

Polymeric surfactants display different capabilities in migration rules and emulsifying crude oil as compared with that of traditional polymers attributing to the co-existence of hydrophilic and hydrophobic groups in molecular chains. To investigate the migration rules of polymeric surfactants in porous media and the matching relationship between polymeric surfactants and porous media, seepage-behavior experiments of different concentrations of polymeric surfactants in different permeability and different length cores were first carried out. The generation of emulsified oil droplets with the polymeric surfactants was then elucidated by comparing core flooding experiments with different injection rates, different saturated oil types and different polymeric surfactants concentrations. The flow characteristics of the emulsion and displacement mechanisms were evaluated by microscopic displacement experiments. The results showed that unlike polymers, when the polymeric surfactant was transported in porous medium, the pressure was difficult to reach a stable state. Based on the matching coefficient, the migration rules of polymeric surfactants in porous media could be defined as high blocking weak flow mode (λ < 14.7), a blocking flow equalization mode (14.7<λ < 19.7) and a smooth flow mode (λ > 19.7). The main reasons for the formation of polymeric surfactants emulsions are a certain shearing action, the snapping action of hydrophobic microdomains on residual oil droplets and assisted effect of colloidal asphaltene. Capillary number(Nc) was used as an evaluation index to divide the emulsification action into four zones: non-emulsified zone(Nc < 2.18 × 10−5), high-efficiency emulsification zone (2.18 × 10−5<Nc < 8.7 × 10−5), optimal-emulsification zone (8.7 × 10−5<Nc < 1.46 × 10−4) and emulsified excess zone(Nc > 1.46 × 10−4). The emulsion microscopic flooding experiment showed that in the porous medium, the transport characteristics of polymeric surfactants emulsion were mainly plugging action of single large emulsion particle, stacking and plugging action of small emulsion particles, forming “emulsion bridge” to block super large pores and vortex action of different sizes emulsion particles.

Pore-level investigations on the oil displacement mechanisms of a viscoelastic surfactant in porous media

A good understanding of pore-level oil displacement mechanisms is of great significance for the application of viscoelastic surfactants (VES) in enhanced oil recovery (EOR). The focus of this paper is on the pore-level events that happen when VES displaces residual oil in porous media. Attention was placed on the displacement dynamics and the relation with the bulk solution properties of VES. Hence, direct measurements of interfacial tension (IFT), contact angle and relative permeability were first performed. The results showed that the tested VES could reduce the oil-water IFT to a 10−2 mN/m level and reverse an initially oil-wet surface to water-wet state. In the visual micromodel experiments, a series of displacement scenarios were created, in which the residual oil was respectively displaced by brine, glycerol, KPS (a common surfactant) and VES aiming to identify the differentiations. The recorded images showed that glycerol was mainly to correct the mobility of the displacing phase via increasing the viscosity. In contrast, KPS was able to strip the adsorbed oil film on pore walls in the water swept zone corresponding to the effect wettability alteration. The EOR mechanism of VES when flow through the porous media can be described as two effects: "dragging" the oil film from the pore wall surface by electrochemical action, and "scretching" the residual oil out of the pore throat by the viscoelastic effect. These observations proved microscopically that the EOR mechanisms of the VES were contributed to synergistic effect of reducing interfacial tension, wettability alteration, mobility correction and viscoelastic flow.

Nanoparticle-enabled delivery of surfactants in porous media

The adsorption of surfactants on the reservoir rocks surface is a serious issue in many energy and environment related areas. Learning from the concept of drug delivery in the nano-medicine field, this work proposes and validates the concept of using nanoparticles to deliver a mixture of surfactants into a porous medium. TiO2 nanoparticles (NPs) are used as carriers for a blend of surfactants mixtures including anionic alkyl aryl sulfonic acid (AAS) and nonionic alcohol ethoxylated (EA) at the optimum salinity and composition conditions. The transport of NPs through a core sample of crushed sandstone grains and the adsorption of surfactants are evaluated. By using TiO2 NPs, the adsorption of surfactant molecules can be significantly reduced, i.e. half of the initial adsorption value. The level of surfactant adsorption reduction is related to the NPs transport capability through the porous medium. An application study shows that comparing to surfactant flooding alone, the total oil recovery can be increased by 7.81% of original oil in place (OOIP) by using nanoparticle bonded surfactants. Such work shows the promise of NP as an effective surfactant carrier for sandstone reservoirs, which could have many potential applications in enhanced oil recovery (EOR) and environmental remediation.

Static Adsorption and Retention of Viscoelastic Surfactant in Porous Media: EOR Implication

The mass loss of surfactant during flowing through porous media is one of the major concerns to surfactant-based Enhanced Oil Recovery (EOR) techniques and also a critical issue for viscoelastic surfactant (VES), which is a novel and promising flooding agent compared against the traditional displacing chemicals. This paper comprehensively investigated the interactions between a VES and several minerals. The static adsorption tests of VES on quartz, montmorillonite and kaolinite were first carried out at 65 °C. Empirical models were established to describe the VES adsorptive isothermal beahviors on the mineral surfaces. The data indicated that the VES showed L, S and LS adsorption isotherm patterns on quartz, montmorillonite, and kaolinite, respectively. The adsorption of VES was notably influenced by temperature, pH value, salinity and Ca2+. As a result of adsorption on clay surfaces, the viscosity and surface activity of the VES solution were significantly decreased. Moreover, the large hydrodynamic size...

Multiphase flow and wettability effects of surfactants in porous media

The concept of enhancing oil recovery from petroleum reservoirs, by reducing oil–water interfacial tension (IFT) using surfactants, is an old one. The main mechanism involved there is the alteration of oil–water relative permeability characteristics, due to reduction in interfacial tension between the two immiscible fluids competing to flow through the porous medium of reservoir rocks. In order for this mechanism to yield effective results, in terms of oil recovery enhancement, the surfactants used must be capable of lowering the oil–water interfacial tension by four to six orders of magnitude. This imposes such requirements of surfactant type, concentration and quantity that the process becomes uneconomical in practice. Another aspect of the use of surface-active agents that has received little attention is their ability to alter wetting preference of the rock surface in relatively dilute concentrations. Such wettability alterations could yield considerable shifts in oil–water distribution and flow characteristics in porous media resulting in far more beneficial effects than can be realized by reduction of interfacial tension alone. In this paper, we present the results of experiments involving flow through porous media using different rock–fluid systems, so chosen as to allow us to differentiate between the relative effects of interfacial tension reduction and wettability alteration on oil–water flow behavior and oil recovery. In addition to confirming and quantitating the beneficial effects of wettability alteration by surfactants on oil recovery, this study has identified an ability of some surfactants to render a unique type of fluid distribution in porous media that enables the preferential draining of the oil phase through formation of oil films on the rock surface.

Modelling surfactant-enhanced remediation of polycyclic aromatic hydrocarbons

Within the framework of a comprehensive investigation concerning the use of surfactants to enhance the in situ remediation of polycyclic aromatic hydrocarbons (PAH) contaminations in the subsurface, SMART (Streamtube Model for Advective and Reactive Transport), a multicomponent transport model, was developed to study the processes (interactions) taking place when surfactants and PAH migrate through porous media as solutes. The model is an adaption of a Lagrangian method allowing for separate treatment of conservative transport and reactive processes. It accounts for the hydraulic as well as physico-chemical heterogeneity of porous aquifers. The system of processes implemented in the model has been shown to be able to represent the behaviour of PAH and surfactants in porous media at the laboratory scale. Here the transport model is applied to a simplified two-dimensional remediation scenario (field scale). It is shown how surfactants may influence the clean-up of PAH contaminated aquifers. Emphasis is put on the effect of hydraulic and physico-chemical aquifer properties on the coupled transport of PAH and surfactants.

Numerical Approach to Statistical Mechanics of Surfactants in Porous Media: A Coarse Grained Description

We present a numerical scheme for Monte Carlo Simulation (MC) of ternary microemulsions, which consist of oil, water and surfactants, confined inside a porous medium such as vycor glass. The model porous medium has been created using the Cell Dynamical Scheme (CDS) while the microemulsion has been modeled following the Larson prescription.

Convection, Dispersion, and Adsorption of Surfactants in Porous Media

Abstract Using the theory of volume averaging, we have shown1 that molecular diffusion, mass tortuosity, and mechanical mixing contribute to the mass-dispersion coefficient. A series of experiments were conducted on the system Triton X-100TM surfactant, n-decane oil, and water to determine the contribution of each mechanism to the total-dispersion matrix for flow through fired Berea sandstone. The dynamics of adsorption and the effect of dead-space volume are considered for the single-phase transport of surfactant through fired Berea. A new dynamic asdorption model is developed which considers both mass transfer to the fluid/solid surface and a kinetic surface-adsorption mechanism. Both kinetic adsorption and mass-transfer rate mechanisms are shown to be important over a wide range of injection rates.