Achinta Bera

Microemulsions: a novel approach to enhanced oil recovery: a review

The trend of growing interest in alternative source of energy focuses on renewable products worldwide. However, the situation of petroleum industries in many countries needs much concern in improving the oil recovery technique. Chemical method, especially microemulsion flooding, plays an important role in enhanced oil recovery technique due to its ability to reduce interfacial tension between oil and water to a large extent as well as alter wettability of reservoir rocks. Surfactant-based chemical systems have been reported in many academic studies and their technological implementations are potential candidates in enhanced oil recovery activities. This paper reviews the role of different types of surfactants in enhanced oil recovery, structure of microemulsion, phase behavior of oil–brine–surfactant/cosurfactant systems with variation of different parameters such as salinity, temperature, pressure and physicochemical properties of microemulsions including solubilization capacity, interfacial tension, viscosity and density under reservoir conditions. The enhanced oil productivity by microemulsion flooding with different surfactant/cosurfactant systems has also been discussed in this paper. This review introduces a new opening in enhanced oil recovery by microemulsion flooding with some new aspects.

Effect of Polymer Adsorption on Permeability Reduction in Enhanced Oil Recovery

In order to reduce the permeability to water or brine, there is a possibility of polymer injection into the reservoir. In the present work, special focus has been paid in polymer [partially hydrolyzed polyacrylamide (PHPA)] injection as a part of chemical method. Tests were conducted in the laboratory at the ambient temperature to examine the reduction in permeability to water or brine in the well-prepared sand packed after the polymer injection. The experiments were performed to study the effect of polymer adsorption on permeability reduction by analyzing residual resistance factor values with different concentrations of polymer solutions. The rheological behavior of the polymer has also been examined. The experimental results also indicate that the adsorption behavior of polymer is strongly affected by salinity, solution pH, and polymer concentration. To investigate the effect of polymer adsorption and mobility control on additional oil recovery, polymer flooding experiments were conducted with different polymer concentrations. It has been obtained that with the increase in polymer concentrations, oil recovery increases.

Anionic–Nonionic Mixed Surfactant Systems: Micellar Interaction and Thermodynamic Behavior

The interactions between an anionic surfactant, viz., sodium dodecylbenzenesulfonate and nonionic surfactants with different secondary ethoxylated chain length, viz., Tergitol 15-S-12, Tergitol 15-S-9, and Tergitol 15-S-7 have been studied in the present article. An attempt has also been made to investigate the effect of ethoxylated chain length on the micellar and the thermodynamic properties of the mixed surfactant systems. The micellar properties like critical micelle concentration (CMC), micellar composition (XA), interaction parameter (β), and the activity coefficients (fA and fNI) have been evaluated using Rubinghs regular solution theory. In addition to micellar studies, thermodynamic parameters like the surface pressure (ΠCMC), surface excess values (ΓCMC), average area of the monomers at the air–water interface (Aavg), free energy of micellization (ΔGm), minimum energy at the air–water interface (Gmin), etc., have also been calculated. It has been found that in mixtures of anionic and nonionic secondary ethoxylated surfactants, a surfactant containing a smaller ethoxylated chain is favored thermodynamically. Additionally, the adsorption of nonionic species on air/water interface and micelle increases with decreasing secondary ethoxylated chain length. Dynamic light scattering and viscometric studies have also been performed to study the interactions between anionic and nonionic surfactants used. GRAPHICAL ABSTRACT

The Effect of Rock-crude Oil-fluid Interactions on Wettability Alteration of Oil-wet Sandstone in the Presence of Surfactants

The aim of the present work was to study the rock-fluid interaction in presence of surfactants and thereby their effects on wettability alteration of oil-wet sandstone for its essentiality in enhanced oil recovery. Characterization of sandstone sample and its interaction with crude oil, brine and surfactants were investigated by Fourier Transform Infrared spectroscopy. Scanning electron microscope and X-ray diffraction studies were performed to characterize the sandstone sample. Critical micelle concentrations of sodium dodecyl sulfate, cetyltrimethylammonium bromide, Tergitol 15-S-7, Tergitol 15-S-9, and Tergitol 15-S-12 were determined by interfacial tension measurement method. Wettability alteration of sandstone was studied by contact angle method.

Modeling of flow of oil-in-water emulsions through porous media

Formation and flow of emulsions in porous media are common in all enhanced oil recovery techniques. In most cases, oil-in-water (O/W) emulsions are formed in porous media due to oil–water interaction. Even now, detailed flow mechanisms of emulsions through porous media are not well understood. In this study, variation of rate of flow of O/W emulsions with pressure drop was studied experimentally, and rheological parameters were calculated. The pressure drop increases with an increase in oil concentration in the O/W emulsion due to high viscosity. The effective viscosity of the emulsion was calculated from the derived model and expressed as a function of shear rate while flowing through porous media. Flow of O/W emulsions of different concentrations was evaluated in sand packs of different sand sizes. Emulsions were characterized by analyzing their stability, rheological properties, and temperature effects on rheological properties.

Numerical Simulation of Enhanced Oil Recovery by Alkali-surfactant-polymer Floodings

In the present study numerical simulation of sand pack flooding with alkali–surfactant–polymer for enhanced oil recovery has been studied using an advanced compositional simulator named STARS available from the Computer Modeling Group. The flooding experiment shows that the chemical formulations are able to recover additional oil more than28% with proper formulation. Therefore, the main motivation of the work is simulation and comparison of results. Different chemical slugs such as alkali, surfactant, and polymer were taken and their effects on water cut, oil cut, cumulative recovery and additional recovery were simulated by the software using experimental data. The results obtained using the simulator has been compared with the available sand packed flooding laboratory experimental data.

Characterization and application of methylcellulose and potato starch blended films in controlled release of urea

Abstract Biodegradable blended films from methylcellulose (MC) and potato starch (PST) have been developed by the casting process. In the present work the influences of concentrations of MC and PST on rheological properties, swelling, mechanical properties such as tensile strength, percentage elongation at break and water vapor transmission rate (WVTR) of the prepared blended films have been studied. Fourier transform infrared (FTIR) analysis of pure MC, PST, their mixture and the mixture with glutaraldehyde and urea was performed to investigate the interactions in blended films. The blended films of MC and PST showed an increase in tensile strength due to the cross linking reactions of the amylopectin molecule of PST in the physical gel state. The change of percentage elongation at break increased with MC concentration and the opposite trend was found in the case of the WVTR due to the network structure of the blended films. The blended films showed a large improvement in the abovementioned properties compared with each single component, due to the interaction formed between hydroxyl groups of PST and the methoxy groups of MC. Experiments were also conducted to investigate the controlled urea release through blended films and the kinetics of the process. Interesting results were found with the prepared MC and PST blended films.