Alpha Olefin Sulfonate Research Articles

Stability and texture of CO2/N2 foam in sandstone

In this study, oil-free steady-state foam flooding experiments were performed in a sandstone core above the supercritical conditions of CO2 using two different surfactants – fluorosurfactant FS-51 and alpha-olefin-sulfonate (AOS). Effect of addition of N2 to sc-CO2-foam in different proportions on stability and structure of CO2/N2 was investigated with the two different surfactants. Co-injection of all three fluids – surfactant, CO2 and N2 was performed and pressure drop (ΔP) data across the core was recorded and foam images were captured through a visual cell and analyzed using ‘ImageJ’ image analysis software. Interfacial tension experiments were also performed at same pressure and temperature conditions as foam-flooding experiments to determine the critical micelle concentration (CMC) of the two surfactants. The surfactants were injected above their CMC’s during foam-flooding experiments.Results from the foam-flooding experiments showed improvement in foam strength as N2 is added to CO2 above its supercritical conditions. The improvement in foam strength was evident by increase in steady-state pressure drop (ΔP) across the core. Analysis of captured foam images also provided evidence of increasing foam strength as the circularity of foam bubbles was significantly enhanced with addition of N2.This study aims to provide a solution to the problem of weakening of sc-CO2-foam. The number of CO2-EOR projects around the world is increasing in lieu with the need of CO2 sequestration. The results from this study provide a safe and effective method to improve CO2-foam at high pressure and temperature reservoir conditions. The results from this study could develop CO2-foam EOR potential and help in keeping as much as CO2 below the ground.

An experimental study of nanoparticle-polymer-stabilized CO2 foam

The results of foam flooding in enhanced oil recovery (EOR) practices depend largely on the stability of foam flow within reservoirs. To stabilize foam, polymers such as partially hydrolyzed polyacrylamide are added to the foaming agents. However, due to residual polymer, which tend to expand in volume within the porous medium, formation damage is inevitable. Thus, new foaming agents are required to stabilize foam without causing formation damage. Nanoparticle-stabilized foams offer promise as suitable substitutes for polymers as they do not damage the formation.The main objective of this work is to improve CO2 foam stability by using nanoparticles such as SiO2 and Fe2O3 in combination with guar-gum polymer. Zeta potential and contact angles of these components were measured to better understand the parameters that affect CO2 foam stability. Experimental outcomes of this work show that the addition of nanoparticles to alpha olefin sulfonate (AOS) and guar-gum solutions can considerably enhance CO2 foam stability. Polymer/surfactant solutions such as guar-gum/AOS generate foams with half-life time significantly shorter than that of the surfactant-nanoparticle dispersion like AOS-SiO2. That is, under same conditions, polymer-surfactant based foams are less stable compared to surfactant-nanoparticle based foams.

Influence of alkyl chain length of alpha olefin sulfonates on surface and interfacial properties

ABSTRACTAlpha olefin sulfonates (AOS) with various alkyl chain lengths have been used to investigate the influence of alkyl chain length on the interfacial properties at air–water, liquid paraffin–water, and parafilm–water interfaces. It was found that the critical micelle concentration decreased with increasing alkyl chain length, while the efficiency of reducing surface tension was inverse relationship with alkyl chain length. The diffusion coefficient obviously reduced with an increase of surfactant concentration and alkyl chain length. The C14-16AOS shows better wettability and emulsification than C16-18AOS and C20-24AOS. For foaming properties, the foamability and foam stability dramatically decreased with increasing alkyl chain length.

Removal of pyridine from its wastewater by using a novel foam fractionation column

Many of pyridine compounds are considered as typical hazardous refractory organics due to their acute toxic properties and teratogenic effects. Therefore, it is great significant to develop a separation technology with the characters of low energy consumption and environmental compatibility to efficiently remove pyridine from its wastewater. In this work, foam fractionation was used to remove pyridine from its wastewater and a novel foam fractionation column was designed for enhancing interfacial adsorption by vertical sieve tray and strengthening foam drainage by floating tongue type tray, in which bubble diameter was monitored for adjusting feeding flow rate and air flow rate in the continuous foam fractionation process. By comparing the foam properties and the adsorption properties of three anionic surfactants (sodium dodecyl sulfate, sodium alcohol ether sulfate and sodium alpha-olefin sulfonate), sodium dodecyl sulfate was chosen as the optimal collector to remove pyridine at pH 4.5. Under the optimal operating conditions, the enrichment ratio and removal percentage of pyridine could reach as high as 34.5 and 90.2%, simultaneously. Above results indicated that foam fractionation was a practicable technology to efficiently remove a hazardous material from its wastewater by designing an effective foam fractionation column.

Simulation Studies on the Role of Lauryl Betaine in Modulating the Stability of AOS Surfactant-Stabilized Foams Used in Enhanced Oil Recovery

The stability of foam in the presence of oil is of fundamental interest in enhanced oil recovery processes using foam for mobility control. Experimentally, it is known that lauryl betaine (LB) increases foam stability of certain anionic surfactants, and LB is referred to as a foam booster. However, the molecular basis for this effect is not well understood. Using molecular dynamics simulations, here we study a system of LB and alpha olefin sulfonate (AOS-14), an anionic surfactant that is used as a foam stabilizer. We monitor the area per molecule, a quantity that correlates with the surface shear viscosity, and the surface dilatational modulus to infer the stability of the various mixtures. We find that the influence of LB is nonmonotonic: the area per molecule and surface dilatational modulus have a minimum and maximum, respectively, around 30% LB in the monolayer. We show that this net effect has its basis in two competing effects: the favorable interaction between LB and AOS-14 that tends to shrink th...

Performance Comparison Between Internal Olefin Sulfonates and Alpha Olefin Sulfonates

AbstractComparison of surface and interfacial properties of internal olefin sulfonates (IOS) and alpha olefin sulfonates (AOS) shows that hydrocarbon chain branching has a significant influence on interfacial properties at the air–water, pentadecane–water and parafilm–water interfaces. The isomeric branched IOS shows a higher critical micelle concentration and are more effective in reducing the surface tension at the air–water interface by occupying a larger area per molecule. IOS exhibits better dynamic air–water interfacial properties due to a lower meso‐equilibrium surface tension. The equilibrium interfacial tensions for AOS and IOS have no remarkable difference at the pentadecane–water interface. The water wettability and electrolyte tolerance are enhanced with branched hydrocarbon chain olefin sulfonates.

Surface Dilational Rheology, Foam, and Core Flow Properties of Alpha Olefin Sulfonate

AbstractThe surface tension, surface dilational rheology, foaming and displacement flow properties of alpha olefin sulfonate (AOS) with inorganic salts were studied. The foam composite index (FCI), which reflects foaming capacity and foam stability, is used to evaluate foam properties. It is found that sodium and calcium salts can lead to decreases in AOS surface tension, critical micelle concentration, and molecular area at the gas–liquid interface. Sodium ions reduce the surface dilational viscoelasticity (E) and FCI of AOS, while calcium ions can enhance the E of AOS and make the FCI of AOS reach a maximum. In the solution containing calcium and sodium ions, the FCI of AOS is improved. Crude oil reduces the FCI of AOS. Injection pressure and displacing efficiency of AOS alternating carbon dioxide (CO2) injection are higher than injections of water alternating with CO2 or CO2 alone in low permeability cores.

Influence of Hydrocarbon Chain Branching on Foam Properties of Olefin Sulfonate with FoamScan

AbstractThe influence of surfactant structure on foam properties of internal olefin sulfonate (IOS) and alpha olefin sulfonate (AOS) in aqueous solutions was estimated from measurements of the foamability, foam stability, and foam morphology, as obtained from conductivity and image analyses techniques. It was found that the foamability and foam stability of C16–18 AOS are higher compared to that of C16–18 IOS, indicating that hydrocarbon chain branching decreases the foamability and foam stability. The foamability and foam stability are enhanced with increasing surfactant concentration, which increases the adsorbed quantity of surfactant molecules at the air–water interface. The influence of hydrocarbon chain branching on foam morphology was also investigated. It was found that foam cells produced by branched chain C16–18 IOS are larger than the foam cells generated by straight chain C16–18 AOS.

An experimental investigation of nanoparticle-stabilized CO2 foam used in enhanced oil recovery

Stability of nanoparticle (NP) stabilized CO2 foam using silica and nanoclay, and the resulting improvement in oil recovery are investigated using modified bulk foam tests and flow experiments using a microfluidic device. The size and uniformity of the dispersion of NPs are characterized via Dynamic Light Scattering. The NP-assisted foam properties are evaluated by: (1) modified bulk foam tests where bulk foam is generated using CO2 under approximately 20psi of pressure and its formability and decay (dynamic stability) are recorded as functions of time and (2) foam stability and oil recovery are investigated using a quasi-2D porous medium (microfluidic chip), fabricated based on a 2D representation of a sample of sandstone. The effects of type of NP, particle size, surfactant type and pressure on CO2 foam stability and viscosity and the resulting incremental oil recovery are investigated and discussed. The results show that nanoclay and silica NPs with an Alpha-Olefin Sulfonate (AOS)-Lauramidopropyl Betaine (LAPB) surfactant mixture provide excellent formability and stability (half-life time around four hours) and increased viscosity. The stability and impact of NPs-stabilized foam on recovery in a microfluidic device is explored and reported. Data is collected using an ultra-high resolution full frame image sensor, which allows the entire surface of the model to be unobstructed for observation; images of the entire porous medium are captured while preserving the resolution required to discern features as small as 10μm. The porous medium is approximately 1.4in. in width and 1.6in. in length and the channels are 20μm deep. Results suggest that foam with highest stability (Si-LAPB-AOS) does not provide the best oil recovery performance (a high oil recovery and a low pore volume injected). The novelty of this work lies in its thorough characterization of NPs in stabilizing CO2 foams, investigation of their stability using a modified bulk foam test and examination of their stability and incremental recovery resulting from their use compared to systems without NPs in quasi-2D porous media fabricated based on a two-dimensional representation of a Berea sandstone.

Determination of Anionic Surfactants in Dishwashing Detergents by High-performance Liquid Chromatography

In this study, we developed and validated microanalysis methods for the determination of linear alkylbenzenesulfonate (LAS), sodium lauryl sulfate (SLS), and alpha olefin sulfonate (AOS). The conditions for the analysis of the surfactants using HPLC with FLD, RID, and ELSD detectors were investigated. The methods were validated by determining the linearity, limits of detection (LODs), limits of quantification (LOQs), recovery, precision, and accuracy. LAS analysis by FLD revealed calibration curves that were linear in the range of 10-200 mg/L for an LAS mixture. The calibration curves for C10-C13 had correlation coefficients of 0.995, 0.997, 0.996, and 0.997, respectively. SLS analysis using RID generated a linear calibration curve in the range of 10-300 mg/L. The calibration curve for SLS C12 had a correlation coefficient of 0.9994. AOS analysis using ELSD resulted in a correlation coefficient of 0.9940. For LAS, the LODs and LOQs were 0.09-0.56 and 0.30-1.87 mg/L, respectively. For SLS C12, the LOD and LOQ were 0.07 and 2.33 mg/L, respectively. For AOS C14, the LOD and LOQ were 16.55 and 21.83 mg/L, respectively. The recoveries were 97.17-98.84% for LAS C10-C14, 97.94% for SLS C12, and 96.11% for AOS C14. The established methods provide acceptable precision and accuracy. Our methods could be useful for the detection of anionic surfactants in dishwashing detergents.

Foams With Wettability-Altering Capabilities for Oil-Wet Carbonates: A Synergistic Approach

Summary The goal of this work is to systematically study the effect of wettability alteration and foaming, either acting individually or synergistically, on tertiary oil recovery in oil-wet carbonate cores. Three types of anionic-surfactant formulations were used: alkyl propoxy sulfate (APS), which exhibited low interfacial tension (IFT), wettability alteration, and weak foaming; alpha-olefin sulfonate (AOS), which showed no wettability alteration but good foaming; and a blend of APS, AOS, and a zwitterionic-foam booster, which showed low IFT, wettability alteration, and good foaming. First, contact-angle experiments were conducted on oil-wet calcite plates to evaluate their wettability-altering capabilities. Second, spontaneous imbibitions in a microchannel were performed to study the role of IFT reduction and wettability alteration by these formulations. Third, static foam tests were conducted to evaluate their foaming performance in bulk. Fourth, foam-flow experiments were conducted in cores to evaluate potential synergism between the anionic-surfactant AOS and the zwitterionic surfactants in stabilizing foam in the absence of crude oil. Finally, oil-displacement experiments were performed by use of a vuggy, oil-wet, dolomite core saturated with a crude oil. After secondary waterfloods, surfactant solutions were coinjected with methane gas at a fixed foam quality (gas-volume fraction). Contact-angle and spontaneous-imbibition experiments showed that AOS can act as a wettability-altering surfactant in the presence of sodium carbonate, but not alone. No synergy was observed in foam stabilization by means of the blend of zwitterionic surfactant and AOS solution (1:1) in a water-wet carbonate core. Oil-displacement experiments in oil-wet carbonate core revealed that coinjection of wettability-altering surfactant and gas can recover a significant amount of oil [33% original oil in place (OOIP)] over waterflood. During foam flooding, with AOS as the foaming agent, only a weak foam was propagated in a carbonate core, irrespective of the core wettability. A blend of wettability-altering surfactant, AOS, and zwitterionic surfactant not only altered the wettability of carbonate core from oil-wet to water-wet, but also significantly increased the foam-pressure gradient in the presence of crude oil.

Yielding in Surfactant Suspension Pastes: Effect of Surfactant Type

AbstractIn this work, we study the rheological properties and the yielding behavior of cleaning pastes containing surfactant and abrasive particles, for three different types of surfactants, namely linear alkyl benzene sulfonate (LAS), alpha olefin sulfonate (AOS) and sodium lauryl ether sulfonate (SLES). All the pastes were observed to have soft solid‐like consistency with their elastic modulus significantly greater than the viscous modulus. With around 36 volume percent of particulate matter, the high stiffness of the pastes suggests that particles form a space spanning network. Interestingly, when subjected to oscillatory shear deformation with increasing strain amplitude, the elastic modulus undergoes a decrease in two steps thereby showing a two‐step yielding behavior. It is observed that the first yield stress does not show frequency dependence, and for LAS‐containing paste was the largest followed by AOS‐ and SLES‐containing pastes, respectively. The second yield stress, on the other hand, for all the three pastes is observed to increase with frequency. Careful assessment of the experimental data suggests that the first yielding event is due to rupture of the network which leads to formation of particulate aggregates. The second yielding event is attributed to breakage of aggregates. In both yielding phenomena, surfactants play an important role. Since, the phase behavior of surfactant in water determines the inter‐particle interaction and network density, the nature of surfactant has a pivotal influence on both the yielding phenomena in surfactant suspension pastes used for cleaning purposes.

Study of blended surfactants to generate stable foam in presence of crude oil for gas mobility control

For controlling the viscous fingering in water-alternating gas injection, addition of foam with formation water is more favorable. Use of foam surfactant is one potential solution for reducing gas mobility. The main objective of this research is to generate stable foam for gas mobility control using surfactant blend formulation. Surfactant blends synergistically exhibit better foaming properties than those of individual surfactants. Surfactant blends improve the foam stability and reduces the destabilizing effect of crude oil. Using foam stabilizers may improve foam stability and apparent viscosity; both of these factors are important for improving gas mobility. Alpha olefin Sulfonate (AOSC14-16) was selected as main surfactant, Octylphenol Ethylene Oxide (TX-100) and Lauryl Amido Propyl Amine oxide (LMDO) were selected as additives. Aqueous stability test was performed at 96 °C. Foam stability test was performed in the absence and presence of crude oil. The foam stability and longevity was recorded above the liquid level. Liquid drainage and Foam half-life were noted with respect to time. The mobility reduction factor of three formulations was performed with CO2 by using Berea sandstone cores at 96 °C and 1400 psi. Experimental result showed that surfactant blend of 0.6 % AOS + 0.6 % LMDO was more stable in presence of crude oil and reduced more gas mobility as compared to an individual surfactant of 0.6 % AOS. The maximum generated foam volume and foam half time indicated better performance of the foaming agent. The surfactant blend formulation plays an important role in controlling gas mobility. Strong stability by these formulations indicates that the foam surfactant formulation is of great significance in the field of enhanced oil recovery.

Synthesis, Characterization and Exploratory Application of Anionic Surfactant Fatty Acid Methyl Ester Sulfonate from Waste Cooking Oil

AbstractThe environmentally friendly anionic surfactant fatty acid methyl ester sulfonate (MES) was prepared by esterification of waste cooking oil (WCO), a low‐cost raw material, followed by sulfonation with chlorosulfonic acid. MES production from WCO (W‐MES) gave yields up to 78 %. Such a value is only slightly lower than the one obtained from soybean oil (S‐MES), 82 %, and almost the same as that from reused cooking oil (R‐MES), 76 %. According to the two‐phase titration results, the content of the active component, α‐MES, in S‐MES, R‐MES and W‐MES was equal to 76.82, 69.19 and 66.60 %, respectively. The disalt, RCH(CO2Na)SO3Na, contents were instead 3.2, 3.8 and 4.7 %, respectively. As proved by the results of the FTIR and NMR characterizations, the chemical structure of W‐MES is almost the same as that of S‐MES and R‐MES. The critical micelle concentration of W‐MES is 5.38 mmol/L and the corresponding surface tension is 32.3 mN/m. The hydrophile‐lipophile balance value of W‐MES is 12.33, which indicates that it can form oil/water emulsions. The three MES demonstrated the same adsorption efficiency, yielding a pC20 value of 3.22, and similar foam stability. Their detergency can be up to 75 % at a concentration of 400 mg/kg and the tolerance to Ca2+ is higher than the one exhibited by linear alkylbenzene sulphonic acid and alpha olefin sulfonate. Additionally, W‐MES shows a considerable solubilization capacity towards polycyclic aromatic hydrocarbon as the molar solubilization ratios to pyrene, phenanthrene and acenaphthene in a 30 mmol/L solution are 1.22 × 10−3, 2.67 × 10−3 and 3.81 × 10−3, respectively.

Effects of Surfactant Blend Formulation on Crude Oil-Brine Interaction and Wettability: An Experimental Study

Interfacial tension of reservoir fluids and wettability are important parameters in the process of enhanced oil recovery. These two parameters affect the fluid distribution within reservoir formation. The fluids distribution in the reservoir strongly affects the flow behavior and residual oil recovery. Interfacial tension plays an important role due to its relationship between foam surface energy and foam stability. The wettability by contact angle measurement provides a method for determining fluid interaction and is considered as a basic research than practical tool for analysis of reservoir formation. The main objective of this research study is to determine the effects of interfacial tension and wettability on foam surfactant blend formulations, brine and crude oil. Anionic and nonionic surfactant blend were selected. The interfacial tension test was performed at 85oC. Dynamic interfacial tension of blended surfactant formulations with Malaysian crude oil were measured in fixed brine salinity. The interfacial tension values of tested surfactant blends were found lower than the interfacial tension between brine and crude oil. Interracial tension between crude oil and foam forming surfactant was reduced by using different concentration of surfactant blend. Good values were obtained by the measurement of contact angle between solid and three foam surfactant blend formulations. The interfacial tension and contact angle experimental studies revealed that, the blend of Alpha Olefin Sulfonate and Sodium Dodecyl Sulfonate with Octylphenol Ethylene Oxide play an important role in reducing the interfacial tension at crude oil-brine interface. The reduced interfacial tension and more wetting surface effects indicated that, these foam surfactant formulations are of great importance in the process of residual oil recovery.

Foams Stabilized by In-Situ Surface-Activated Nanoparticles in Bulk and Porous Media

Summary Foams for subsurface applications are traditionally stabilized by surfactants. The goal of this work is to study foam stabilization by nanoparticles—in particular, by in-situ surface-hydrophobization of hydrophilic nanoparticles. The interfacial properties of the nanoparticles were modulated by the attachment of short-chain surface modifiers (alkyl gallates) that render them partially hydrophobic, but still fully dispersible in water. First, static foams were generated with nanoparticles with varying concentrations of surface modifiers. The decay of foam height with time was measured, and half-lives were determined. Optical micrographs of foam stabilized by surface-modified nanoparticles (SMNPs) and surfactant were recorded. Second, aqueous foams were created in-situ by coinjecting the SMNP solutions with nitrogen gas through a Berea sandstone core at a fixed quality. Pressure drop across the core was measured to estimate the achieved resistance factor. These pressure-drop results were then compared with those of a typical surfactant (alpha olefin sulfonate, alkyl polyglucoside) under similar conditions. Finally, oil-displacement experiments were conducted in Berea cores with surfactant and SMNP solutions as foaming agents (coinjection with nitrogen gas). A Bartsch shake test revealed the strong foaming tendency of SMNPs even with a very low initial surface-modifier concentration (0.05 wt%), whereas hydrophilic nanoparticles alone could not stabilize foam. The bubble texture of foam stabilized by SMNPs was finer than that with surfactants, indicating a stronger foam. As the degree of surface coating increased, the resistance factor of SMNP foam in a Berea core increased significantly. The corefloods in the sandstone cores with a reservoir crude oil showed that immiscible foams with SMNP solution can recover a significant amount of oil (20.6% of original oil in place) over waterfloods.

Foam Flow Experiments. I. Estimation of the Bubble generation-Coalescence Function

Gas injection leads to foam formation in porous media in the presence of surfactant solutions, which is used for flow diversion and enhanced oil recovery. We present here laboratory experiments of co-injecting nitrogen and sodium C14?16 alpha olefin sulfonate with two concentrations: 20× the critical micelle concentration (CMC) in an unconsolidated sandpack of 1860 Darcy and at the CMC for a Bentheimer sandstone of 3 Darcy. The steady state profile for the unconsolidated sandpack is achieved after 1.3 pore volumes, whereas for Bentheimer sandstone, steady state is obtained after injection of 12–15 pore volume. A model that leads to four equations, viz., a pressure equation, a water saturation equation, a bubble density equation and a surfactant transport–adsorption equation, is used to explain the experimental pressure drop. It is asserted that the experimental pressure drop across the measurement points can be used to obtain a first estimate of the average bubble density, which can be further used to obtain part of the source term in the bubble density equation. If we consider flowing fraction of foam, the rate of change of bubble density during transient state can be equated to the bubble density generation-coalescence function plus the terms accounted for bubble transport by convection and diffusion divided by porosity and saturation.

Sodium Alpha Olefin Sulfonate Modified Carbon Paste Electrode Sensor for Dopamine: A Voltammetric Study

Sodium alpha olefin sulfonate, an anionic surfactant was modified in carbon paste electrode by immobilization technique. The surfactant modified carbon paste electrode (SAOS/MCPE) was applied for the electrochemical determination of dopamine. The modified electrode shows excellent electrocatalytic property towards DA at pH 7.2 in Phosphate Buffer solution (PBS). The effects of scan rate and concentration of dopamine was studied and the electrode process was adsorption-controlled processes. The modified electrode resolves the welldefined two peaks for dopamine and ascorbic acid which is absent for bare carbon paste electrode and simultaneous studies was studied by cyclic and differential pulse voltammetric techniques. The detection limit was found to be 1.051 × 10-6 M respectively and the modified electrode shows good sensitivity and selectivity for dopamine.

Effectiveness of foam-gel formulation in homogenizing the CO2 front during subsurface sequestration

Underground sequestration of carbon dioxide uniformly all over the designated geo-formation requires use of sealant formulation in large volume. Thin channels, cracks or fractures that otherwise would have allowed a by-pass of CO2 needs to be sealed a priori. Use of a mobile hydrogel formulation that gets crosslinked over time inside the channel may be used as a sealant. Introduction of gas phase in the form of small bubbles during placement may reduce the density of the formulation, help in reaching the hard-to-reach places near the caprock, and reduce the material cost of the treatment. The surfactant and the polymer in the aqueous phase may help in stabilizing the bubbles till the cross-linked network becomes immobile for blocking unwanted flow. The paper addresses the effectiveness of foam-gel layer in sealing reservoir fractures. Partially hydrolyzed polyacrylamide was crosslinked by chromium triacetate in presence of alpha olefin sulfonate as surfactant. The introduction of gas bubbles using a fluidic arrangement, the self-alignment of bubbles on a petridish, and the alignment under the confinement of a thin channel respectively are studied here. The stability of the composite film during shut-in period, and when subjected to water or CO2 pressure were evaluated. The rupture process and the hindered flow of injected phase at the post-rupture stage were characterized. Laser based volumetric images and the pressure gradients along the channel helped in ascertaining the flow path, and intrinsic flow resistances. The foam gel layer could withstand a CO2 pressure gradient of 0.7 kg/cm2 over a length of 30.48 cm without rupture. When the pressure exceeded the rupture pressure, an aperture equivalent to 1/10th of the distance between the two walls opened up for hindered flow of CO2.

Static and dynamic foam/oil interactions: Potential of CO2-philic surfactants as mobility control agents

Abstract Examination of the nature and extent of CO2 foam/oil interactions is essential for the successful design and application of surfactants in foam assisted water alternating gas (FAWAG) process. A structure–property relationship of surfactants based on theoretical method, static bulk tests, and dynamic displacements in porous media subjected to foam flooding is provided in this study. Surfactants with an increased affinity towards CO2 are intended to improve foam mobility control mechanism in a Malaysian oil reservoir. Two anionic foaming agent surfactants (in-house developed FomaxII and industry benchmark alpha olefin sulfonate (AOS)), and two CO2-philic surfactants (in-house developed FomaxVII and UTP-Foam) are selected to investigate the effect of surfactant tail groups on the phase interactions in a system of CO2-oil-brine. The effect of surfactant presence on the CO2/water and oil/water interfaces under reservoir conditions is measured by using a high pressure, high temperature tensiometer. Surfactants with higher tolerance against oil are selected based on static stability column tests and the equilibrium spreading coefficients model. The surfactant alternated with gas (SAG) displacements are then conducted by using the selected CO2-philic surfactants dissolved in injection brine to study the interactions of foam and oil in porous media at the reservoir conditions. A relationship was observed between foam stability column tests and the prediction results of the spreading theory, which can be a useful preliminary screening of an oil-resistant foam. The performance of foam during injection of surfactants in sandstone cores was also supporting the preliminary screening results. However, it was shown to be dependent on different parameters (such as formation of macroemulsion once foam lamellae ruptures, and surfactant–rock surface interactions), which are not necessarily observed in the static tests results. Macroemulsion once formed hindered the performance of subsequent FomaxVII surfactant slugs to produce foam.