Petroleum Recovery Research Articles

Optimizing the Clearance Fit of a Progressive Cavity Pump for the Thermal Recovery of Petroleum Using Fluid-Structure Thermal Coupling.

It is important to incorporate the effects of fluid–structure thermal coupling and the boundary conditions when calculating the thermal dynamics and response of progressive cavity pumps. This study develops a fluid–structure thermal coupling model of the progressive cavity pump to improve the accuracy of its measured field of deformation and the temperature field of the stator. A function for the macroscopic motion of a rigid body is written in a typical fluid domain, and the user-defined function (UDF) in FLUENT is used to load the boundary of the rotor to realize its planetary motion. Local remeshing is used to update the moving grid, and the viscoelastic hysteretic heat of the stator is treated as the internal source of heat. One-way decoupling is used based on tire slip theory, and heat flux on the surface of the stator is calculated by the ANSYS Parametric Design Language (APDL). The sequential fluid–structure thermal coupling of the progressive cavity pump is calculated by using the ANSYS workbench. A scheme for optimizing the fit clearance of the stator and rotor is given to improve the volumetric efficiency of the progressive cavity pump and prevent the stator from being stuck owing to a large deformation, and the calculations are verified by experiments on volumetric efficiency. The average deviation in the calculated volumetric efficiency was less than 5% compared with the experimental values. The proposed scheme provides a theoretical basis for the optimal design of the progressive cavity pump for the thermal production of petroleum.

Practical Mathematical Model for the Evaluation of Main Parameters in Polymer Flooding: Rheology, Adsorption, Permeability Reduction, and Effective Salinity.

Polymer flooding is one of the most used chemical enhanced oil recovery (CEOR) technologies worldwide. Because of its commercial success at the field scale, there has been an increasing interest to expand its applicability to more unfavorable mobility ratio conditions, such as more viscous oil. Therefore, an important requirement of success is to find a set of design parameters that balance material requirements and petroleum recovery benefits in a cost-effective manner. Then, prediction of oil recovery turns out to handle more detailed information and time-consuming field reservoir simulation. Thus, for an effective enhanced oil recovery project management, a quick and feasible tool is needed to identify projects for polymer flooding applications, without giving up key physical and chemical phenomena related to the recovery process and avoiding activities or projects that have no hope of achieving adequate profitability. A detailed one-dimensional mathematical model for multiphase compositional polymer flooding is presented. The mathematical formulation is based on fractional flow theory, and as a function of fluid saturation and chemical compositions, it considers phenomena such as rheology behavior (shear thinning and shear thickening), salinity variations, permeability reduction, and polymer adsorption. Moreover, by setting proper boundary and initial conditions, the formulation can model different polymer injection strategies such as slug or continuous injection. A numerical model based on finite-difference formulation with a fully implicit scheme was derived to solve the system of nonlinear equations. The validation of the numerical algorithm is verified through analytical solutions, coreflood laboratory experiments, and a CMG-STARS numerical model for waterflooding and polymer flooding. In this work, key aspects to be considered for optimum strategies that would help increase polymer flooding effectiveness are also investigated. For that purpose, the simulation tool developed is used to analyze the effects of polymer and salinity concentrations, the dependence of apparent aqueous viscosity on the shear rate, permeability reduction, reversible–irreversible polymer adsorption, polymer injection strategies on petroleum recovery, and the flow dynamics along porous media. The practical tool and analysis help connect math with physics, facilitating the upscaling from laboratory observations to field application with a better-fitted numerical simulation model, that contributes to determine favorable scenarios, and thus, it could assist engineers to understand how key parameters affect oil recovery without performing time-consuming CEOR simulations.

Biosurfactant Production from Pseudomonas aeruginosa ATCC27853 with Carbon Source from Crude Palm Oil for Oil Recovery

Biosurfactants are surfactants that are synthesized by microorganisms using organic materials and have biodegradable properties, making them environmentally friendly. One of the applications of biosurfactants in the recovery of petroleum. This study aims to determine the type of biosurfactant produced by Pseudomonas aeruginosa bacteria using crude palm oil as the main carbon source, to determine the effect of variations in pH and CPO concentration on surface tension reduction and emulsification, and compare the best biosurfactant with surfactant synthesis. The production of biosurfactants has 3 stages, namely the bacterial preparation, the biosurfactant production, and the analysis in the form of surface tension, emulsification, crude oil removal, and FTIR. The best biosurfactant was obtained at pH 7 and a carbon source concentration of 3% v/v with surface tension and emulsification values ​​of 42.49 mN/m and 58%, respectively. The pH value and CPO concentration can affect the growth in the biosurfactant production process, thus also affecting the surface tension and emulsification values. The biosurfactants obtained were rhamnolipid biosurfactants. The biosurfactants produced in this study have lower crude oil recovery capabilities than synthetic surfactants with crude oil removal values ​​of 57.78% and 79.34%, respectively.

Innovative technologies to remove alkylphenols from wastewater: a review

Alkylphenols and alkylphenol polyethoxylates are emerging hazardous contaminants due in particular to their endocrine-disrupting properties. These compounds originate from consumer products such as paints and latex paints, adhesives, inks, formulation of pesticides, paper industry, textile and leather industry, petroleum recovery chemicals, metal working fluids, personal care products, washing agents, cleaners, and detergents. Since classical wastewater treatments have not been designed to remove alkylphenols, these compounds end up polluting ecosystems. Here we review three advanced methods to remove alkylphenols and derivatives. First, innovative polymers, such as cyclodextrin polymers and molecularly imprinted polymers, allow to remove alkylphenols from effluents by adsorption. Second, biotechnologies such as microalgae, biodegradation in constructed wetlands and sequential anaerobic–aerobic digestion treatments. Third, advanced oxidation processes to degrade recalcitrant alkylphenols, e.g., ozone-carbon coupling, electrochemical degradation, photocatalysis, zero-valent iron-activated persulfate coupling, and catalytic ozonation.

Quantitative Evaluation of Well Performance Affected by Fracture Density and Fracture Connectivity in Fractured Tight Reservoirs

Understanding the relationship between petroleum recovery and characteristics of hydraulic fracture network is a key component of economic development of tight reservoirs. Owing to the limitations inherent in current reservoir simulators, optimization of fracture network has been simply focused on the parameters of fracture conductivity, fracture number, aperture, and so on. Deeper insight into the effect of decisive parameters, such as fracture density and fracture connectivity on the well production in tight reservoirs, is now required to maximize the petroleum recovery. In this work, a newly developed discrete fracture simulator is applied to comprehensively study the effect of fracture density and fracture connectivity in tight reservoirs. Conceptual models with different fracture densities and different fracture connectivity are firstly designed and simulated to explore how these two parameters affect the reservoir behavior and establish the equations for effect measurement. Then, we simulate models with different well placement strategies and a fixed set of natural fractures to determine the optimal strategy. Finally, simulations are performed on a field-scale reservoir with three long fractured horizontal wells. Results demonstrate that increases in either fracture density or fracture connectivity can significantly improve well production. However, an optimal value exists considering the economic profit. Compared to the fracture density, fracture connectivity plays a more important role in affecting the well production. In a tight reservoir with abundant natural fractures, making the horizontal well parallel to the direction of natural fractures is determined to be the optimal well placement strategy. The heterogeneous distribution of remaining oil in real tight oil reservoirs is mainly caused by the heterogeneous distribution of fracture density and fracture connectivity.

THE INFLUENCE OF ALCOHOL TYPE AND CONCENTRATION ON THE PHASE BEHAVIOR AND INTERFACIAL TENSION IN OIL-SURFACTANTCOSURFACTANT-BRINE MIXTURE SYSTEM

The number of mechanism is limited for reducing the entrapment of oil in the pore space of reservoir rock and for mobilizing that residual which remains entrapped, thereby improving the microscopic displacement efficiency of a petroleum recovery process. After primary recovery by flow powered by the energy stored in the compressed fluids of reservoir, and secondary recovery by injection-pump driven water flooding, residual oil is trapped by the capillary pressure developed by interfacial tension in curved menisci between oil and water in the pore space. Figure 1.1 illustrates the interplay of capillary and viscous forces in the water flooding process. Shown in the figure is water displacing oil. The important point is that residual oil is trapped in the pore space by interfacial tension. To improve micros- copic displacement efficiency is to reduce interfacial tension between oil and water. Surfactant is surface active agent chemical that has two types of properties; lypofob (like water) and hydrofob (like oil). The value of interfacial tension between oil and water is high, when surfactant is dissolved into water and contacts with oil, so that surfactant is not only soluble in the water, but also it is soluble in the oil. By addition of surfactant into the water and contact with oil can result in interfacial tension between oil and water from high (more less 20 - 30 dyne/cm) to lower interfacial tension (10-2 dyne/cm). To change the lower interfacial tension to the lowest interfacial tension conditions (10-4dyne/cm), cosurfactant in oil-surfactant-brine mixture is used. Alcohols are widely used in micellar surfactant systems for enhanced petroleum recovery and are variously called cosurfactant or cosolvent. In general, alcohols modify the physico- chemical properties in ways that are important to the design of surfactant-based process for improving petroleum recovery. This research is focused on alcohol effects on oil-surfactant-brine phase behavior and interfacial tension of oil-surfactant-brine system.

Optimizing Clearance Fit of Screw Pump for Thermal Recovery of Petroleum Using Fluid–Structure Thermal Coupling

Optimizing Clearance Fit of Screw Pump for Thermal Recovery of Petroleum Using Fluid–Structure Thermal Coupling

How pH induced surface charge modification explains the effect of petrophysical and hydrological factors on recovery trends of water drive gas reservoirs

It is generally known that water drive oil reservoirs are more efficient than water drive gas reservoirs. In the petroleum literature, several studies have documented recovery trends based on petrophysical factors other than the wettability factor.Consistent with the high concentration of carbon dioxide in natural gas systems, the pH induced wetting transition reported in petroleum recovery research associated with low salinity water flooding is a potential factor that can impact gas recovery from natural gas systems. In this paper, we have reviewed extensively the fundamental aspects of pH induced wetting transition associated with surface charge regulation in different lithologies. In so doing, we have developed theoretical models that aid explanation of gas recovery trends from different lithologies associated with natural gas systems under aquifer drive. Most importantly, putting our models in the context of fundamental theories associated with pH induced surface charge modification, we have successfully correlated the literature based wetting transition trends of gas recovery to petrophysical properties of absolute permeability and rock type as well as hydrological effect associated with aquifer type.

Study on three-dimensional immiscible water–Oil two-phase displacement and trapping in deformed pore structures subjected to varying geostress via in situ computed tomography scanning and additively printed models

Accurate understanding and quantitative characterization of the three-dimensional (3D) immiscible water–oil two-phase displacement process and of the factors that affect this process in porous reservoir rocks are prerequisites for the enhancement of petroleum recovery efficiency. To meet these prerequisites, it is crucial to directly visualize and quantify the pore scale physics and dynamic evolution of the water–oil two-phase displacement behavior. However, engineering activities, such as borehole drilling, reservoir fracturing, and oil recovery, can cause geostress redistribution in petroleum reservoirs and drastically change the 3D pore structures of reservoir rocks. This makes it difficult to apply conventional experimental techniques and analytical models to directly reveal and evaluate the 3D immiscible fluid displacement in reservoir rocks during pore structure deformation. In this study, we used X-ray computed tomography, integrated with triaxial loading techniques, to capture in situ the immiscible water–oil displacement and oil trapping inside 3D pore spaces during the deformation induced by various geostresses. An additive manufacturing or 3D printing (3DP) technology was applied to replicate the transparent models of actual porous rocks, facilitating the representation and quantification of pore space deformation and the dynamic process of water–oil displacement and oil trapping. Pore scale displacement behaviors (including water sweeping, fingering effects, preferential flow paths, and oil trapping) and their evolution and pore structure deformation with varying geostress were directly visualized and quantified. The relationships between the characteristics of the deformed structures, water–oil displacement efficiency, and effective geostress changes were formulated. The results indicate that stress-induced pore structure deformation has an evident impact on the 3D water–oil displacement behavior and efficiency. A comparison of the 2D and 3D water-oil displacement behaviors indicates that the 3D model predicts a more realistic displacement performance, whereas the residual oil saturation is overestimated in a 2D pore system owing to the truncation of pore connectivity in the third dimension. This study provides a method for directly visualizing and quantifying the effects of geostress-induced pore deformation on the 3D water–oil displacement in porous reservoirs; this method can help draft a strategy to enhance petroleum recovery.

Fluid particle interaction in packings of monodisperse angular particles

Understanding fluid flow in granular materials is essential for many engineering applications, including petroleum recovery, groundwater movement and embankment stability. This study investigates the influence of particle angularity on permeability and fluid-particle interaction forces. A random shape generator based on spherical harmonics is used to create irregular-shaped particles with different levels of angularity. Granular packings of uniformly sized (monodisperse) particles are then constructed with the discrete element method (DEM), and pore-scale computational fluid dynamics (CFD) simulations are used to determine the flow fields and the resulted fluid-particle interaction. The more angular particle assemblies thus generated are less permeable, and their fluid-particle interaction forces are higher. However, angularity has limited influence on flow rate distribution and flow tortuosity. The influence of angularity is localized. An increase in angularity generates a larger variance of the pressure distribution on the particle surfaces, thus increasing the pressure component of the fluid-particle interaction force.

Preparation of polyoxypropylene surfactant-based nanoemulsions using phase inversion composition method and their application in oil recovery

Emulsification using phase inversion composition (PIC) was achieved by changing the composition of surfactants at a constant temperature. The method has great potential to scale up applications due to the ease in the formation of nanoemulsions and the relatively low energy involved. Surfactants containing composition-sensitive polyoxyethylene (POE) chains are widely used to prepare nanoemulsions using the PIC method. It is, therefore, anticipated that surfactants containing composition-sensitive polyoxypropylene (POP) chains can also be used to prepare nanoemulsions using the PIC method. The POP surfactant D230-2OA, containing short POP chains, was obtained from the electrostatic interactions between hydrophilic POP diamine (D230) and hydrophobic oleic acid (OA). The synthesized D230-2OA was used as an emulsifier in the preparation of the n-dodecane-in-water nanoemulsion using the PIC method. The effects of D230-2OA concentration, oil-to-surfactant weight ratio, and NaCl concentration on the droplet size of the nanoemulsions was investigated using dynamic light scattering (DLS). The morphology of the nanoemulsion was characterized using cryogenic transmission electron microscopy (cryo-TEM). The wettability of the crude oil–saturated quartz plate before and after treatment with nanoemulsions was obtained using contact angle measurement. A core flooding experiment demonstrated the efficiency of the diluted nanoemulsion in enhanced oil recovery, with an additional recovery of 21.30%. The nanoemulsion prepared with the POP surfactant as the emulsifier using the PIC method has wide application in petroleum recovery.

An investigation of the effects of synthesized zinc oxide nanoparticles on the properties of water-based drilling fluid

The deterioration of drilling fluid properties during deep drilling causes problems like inefficient cutting removal, fluid invasion, and shale swelling, which increases non-productive time (NPT) and cost. Recently nanoparticles (NPs) based drilling fluid are introduced to address these impediments since these particles prove their advantages in different stages of petroleum exploration and recovery. Previous developments are concerned with the use of commercial zinc oxide (ZnO) NPs in inorganic KCl salt-based drilling fluid, although application of KCl in drilling fluid arouses environmental complications. In this study, ZnO NPs prepared in the laboratory are used in water-based drilling fluid (WBDF) to assess the effect of nanoparticles on the properties of drilling fluid at two temperature conditions of 40 °C and 80 °C. A base mud is formulated, and ZnO NPs with five different concentrations of 0.05, 0.1, 0.5, 1.0, and 2.0 wt% are mixed with the base mud. The experimental analysis shows that NPs improve the rheological properties of WBDF. When the concentration of NPs was 0.1 wt%, the yield point increased by 61.54% at 40 °C, and when the concentration of NPs was 0.05 wt%, the yield point increased by 60% at 80 °C. Besides, when the concentration of NPs is 0.05 wt%, 10-sec gel strengths are enhanced by 25% and 50% at 40 °C and 80 °C, respectively. The API low-pressure low-temperature (LPLT) filter volume is not significantly affected by the addition of NPs in WBDF. However, mud cake thickness continuously reduces with the increase of NPs concentrations. This result reveals that a superior rheological improvement is achieved at low NPs concentration (0.05 wt%) at higher temperature.

Simulation of the onset of convection in a porous medium layer saturated by a couple-stress nanofluid

Linear and nonlinear stability analyses for the onset of time-dependent convection in a horizontal layer of a porous medium saturated by a couple-stress non-Newtonian nanofluid, intercalated between two thermally insulated plates, are presented. Brinkman and Maxwell–Garnett formulations are adopted for nanoscale effects. A modified Darcy formulation that includes the time derivative term is used for the momentum equation. The nanofluid is assumed to be dilute and this enables the porous medium to be treated as a weakly heterogeneous medium with variation of thermal conductivity and viscosity, in the vertical direction. The general transport equations are solved with a Galerkin-type weighted residuals method. A perturbation method is deployed for the linear stability analysis and a Runge–Kutta–Gill quadrature scheme for the nonlinear analysis. The critical Rayleigh number, wave numbers for the stationary and oscillatory modes, and frequency of oscillations are obtained analytically using linear theory, and the nonlinear analysis is executed with minimal representation of the truncated Fourier series involving only two terms. The effect of various parameters on the stationary and oscillatory convection behavior is visualized. The effect of couple-stress parameter on the stationary and oscillatory convections is also shown graphically. It is found that the couple-stress parameter has a stabilizing effect on both the stationary and oscillatory convections. Transient Nusselt number and Sherwood number exhibit an oscillatory nature when time is small. However, at very large values of time, both Nusselt number and Sherwood number values approach their steady-state values. The study is relevant to the dynamics of biopolymers in solution in microfluidic devices and rheological nanoparticle methods in petroleum recovery.

The Prediction of Future Oil Wells Production from Decline Curve Pattern

The production decline analysis is a traditional method of identifying wells production pattern and predicting its performance and life based on real production data. The study of the application the production decline curves using one of the empirical models either the exponential, hyperbolic or the harmonic decline curves which occur often in the later life of production units has been done. Decline curve analysis applies oil production versus time plots to extrapolate an estimation of the future production rates for wells. Production data were plotted in different ways to identify a representative decline model. In this study, the historical data were provided from five oil wells of the 4th pay formation reservoir in Zubair field in southern Iraq (Basrah region). These data were used to estimate the total future recovery of petroleum and the end of a productive life to the economic limit. The relationships between production rate, time, and cumulative production for each well were studied. The production data points for each well were analyzed separately to evaluate the effect of the change in the production and reservoir conditions on the remaining reserves. The typical decline curve was applied in each oil well and the estimation of total reserves isn‘t changing with the time or by the workover action.

Unsupervised machine learning using 3D seismic data applied to reservoir evaluation and rock type identification

Net reservoir discrimination and rock type identification play vital roles in determining reservoir quality, distribution, and identification of stratigraphic baffles for optimizing drilling plans and economic petroleum recovery. Although it is challenging to discriminate small changes in reservoir properties or identify thin stratigraphic barriers below seismic resolution from conventional seismic amplitude data, we have found that seismic attributes aid in defining the reservoir architecture, properties, and stratigraphic baffles. However, analyzing numerous individual attributes is a time-consuming process and may have limitations for revealing small petrophysical changes within a reservoir. Using the Maui 3D seismic data acquired in offshore Taranaki Basin, New Zealand, we generate typical instantaneous and spectral decomposition seismic attributes that are sensitive to lithologic variations and changes in reservoir properties. Using the most common petrophysical and rock typing classification methods, the rock quality and heterogeneity of the C1 Sand reservoir are studied for four wells located within the 3D seismic volume. We find that integrating the geologic content of a combination of eight spectral instantaneous attribute volumes using an unsupervised machine-learning algorithm (self-organizing maps [SOMs]) results in a classification volume that can highlight reservoir distribution and identify stratigraphic baffles by correlating the SOM clusters with discrete net reservoir and flow-unit logs. We find that SOM classification of natural clusters of multiattribute samples in the attribute space is sensitive to subtle changes within the reservoir’s petrophysical properties. We find that SOM clusters appear to be more sensitive to porosity variations compared with lithologic changes within the reservoir. Thus, this method helps us to understand reservoir quality and heterogeneity in addition to illuminating thin reservoirs and stratigraphic baffles.

Oil-in-water nanoemulsion with reversible charge prepared by the phase inversion composition method

The phase inversion composition (PIC) method is to change the composition of the system to form nanoemulsion under constant temperature conditions. In this work, the nanoemulsion charge was regulated by changing the pH of the system to protonate and deprotonate N, N-dimethyldecanamide (DMDEA). The particle size and stability of the nanoemulsion were characterized by dynamic light scattering (DLS). Zeta potential (ζ) confirmed the electrification of nanoemulsion at different pH. Contact angle measurement revealed the influence of different electrification of nanoemulsion on wettability alteration. The wettability of quartz powder before and after nanoemulsion treatment was analyzed by Fourier-transform infrared spectroscopy (FTIR). The displacement experiment proved the efficiency of nanoemulsion in enhancing oil recovery, and an additional recovery of 17.36% was observed after subsequent water flooding. The prepared nanoemulsion with reversible charge has good application prospects in petroleum recovery.

Capillary equilibrium of bubbles in porous media

In geologic, biologic, and engineering porous media, bubbles (or droplets, ganglia) emerge in the aftermath of flow, phase change, or chemical reactions, where capillary equilibrium of bubbles significantly impacts the hydraulic, transport, and reactive processes. There has previously been great progress in general understanding of capillarity in porous media, but specific investigation into bubbles is lacking. Here, we propose a conceptual model of a bubble's capillary equilibrium associated with free energy inside a porous medium. We quantify the multistability and hysteretic behaviors of a bubble induced by multiple state variables and study the impacts of pore geometry and wettability. Surprisingly, our model provides a compact explanation of counterintuitive observations that bubble populations within porous media can be thermodynamically stable despite their large specific area by analyzing the relationship between free energy and bubble volume. This work provides a perspective for understanding dispersed fluids in porous media that is relevant to CO2 sequestration, petroleum recovery, and fuel cells, among other applications.

Bacterial and archaeal diversity in oil fields and reservoirs and their potential role in hydrocarbon recovery and bioprospecting.

Hydrocarbon is a primary source of energy in the current urbanized society. Considering the increasing demand, worldwide oil productions are declining due to maturity of oil fields and because of difficulty in discovering new oil fields to substitute the exploited ones. To meet current and future energy demands, further exploitation of oil resources is highly required. Microorganisms inhabiting in these areas exhibit highly diverse catabolic activities to degrade, transform, or accumulate various hydrocarbons. Enrichment of hydrocarbon-utilizing bacteria in oil basin is caused by continuous long duration and low molecular weight hydrocarbon microseepage which plays a very important role as an indicator for petroleum prospecting. The important microbial metabolic processes in most of the oil reservoir are sulfate reduction, fermentation, acetogenesis, methanogenesis, NO3- reduction, and Fe (III) and Mn (IV) reduction. The microorganisms residing in these sites have critical control on petroleum composition, recovery, and production methods. Physical characteristics of heavy oil are altered by microbial biotransformation and biosurfactant production. Considering oil to be one of the most vital energy resources, it is important to have a comprehensive understanding of petroleum microbiology. This manuscript reviews the recent research work referring to the diversity of bacteria in oil field and reservoir sites and their applications for enhancing oil transformation in the target reservoir and geomicrobial prospecting scope for petroleum exploration.

Investigations on the adsorption, wettability and zeta potential of anionic surfactant in limestone.

The understanding of the mechanisms that affect oil production in carbonaceous reservoirs has become increasingly necessary, particularly in limestone, which mostly features oil wettability properties that diminishes petroleum recovery. The objective of this work was to investigate the ability of anionic surfactant (coconut oil derived soap) to adsorb in limestone in order to promote wettability change. The finite-bath technique was employed with changes in temperature, mass of adsorbent material (limestone), contact time and surfactant concentration. Contact angle and zeta potential measurements were also made. The surfactant could be significantly adsorbed on the rock, possibly due to ions that are charged oppositely to the species on the rock surface. A temperature rise from 30 °C to 50 °C was unfavourable to the adsorption capacity. The oil-wettable in-natura limestone had its wettability reduced after the treatment with surfactant. The zeta potential measurements showed that electrostatic attractions play an important role in the adsorption process.

Effects of Na2SO4 and Na3PO4 on the surface and thermodynamic properties of an anionic surfactant: bis-(2- ethyl hexyl) sodium sulfosuccinate (AOT) in aqueous solutions

From tensiometric measurements, critical micelle concentration (CMC), maximum surface excess concentration, minimum area per molecule at the air-liquid interface and thermodynamic parameters of micellization have been determined for an anionic surfactant: bis-(2-ethylhexyl) sodium sulfosuccinate (AOT) in aqueous medium. Effects on the above physico-chemical properties due to added electrolytes: Na2SO4 and Na3PO4 over a wide range of the surfactant concentrations and at 288.15, 293.15 and 298.15 K have been described in the light of intermolecular interactions. The CMC of AOT is lowered and the micellar stability is improved upon mixing the above electrolytes in aqueous surfactant solution and the same become more pronounced when divalent SO42- are replaced by trivalent PO43-. These observations may be beneficial for improving efficiency of AOT as a detergent, managing oil spill problem, in froth-flotation process for concentrating ores and for efficient recovery of petroleum in the tertiary process.