Flow characteristics and regime transition of aqueous foams in porous media over a wide range of quality,velocity,and surfactant concentration

Aqueous foam is broadly applicable to enhanced oil recovery(EOR).The rheology of foam as a function of foam quality,gas and liquid velocities,and surfactant concentration constitute the foundation of its application.The great variations of the above factors can affect the effectiveness of N2 foam in EOR continuously in complex formations,which is rarely involved in previous relevant studies.This paper presents an experimental study of foam flow in porous media by injecting pre-generated N2 foam into a sand pack under the conditions of considering a wide range of gas and liquid velocities and surfactant concentrations.The results show that in a wide range of gas and liquid velocities,the pressure gradient contours are L-shaped near the coordinate axes,but V-shaped in other regions.And the surfactant concentration is a strong factor influencing the trend of pressure gradient contours.Foam flow resistance is very sensitive to the surfactant concentration in both the high-and low-foam quality regime,especially when the surfactant concentration is less than CMC.The foam quality is an important variable to the flow resistance obtained.There exists a transition point from low-to high-quality regime in a particular flow system,where has the maximum flow resistance,the corresponding foam quality is called transition foam quality,which increases as the surfactant concentration increases.The results can add to our knowledge base of foam rheology in porous media,and can provide a strong basis for the field application of foams.

Effect of surfactant type on interfacial area and liquid mass transfer for CO_2 absorption in a bubble column

The effect of different surfactants(n-octyltrimethylammonium bromide(OTABr),sodium dodecyl benzene sulfonate(SDBS) and Tween 80) with different critical micelle concentrations(CMC) on the CO_2 absorption into aqueous solutions in a bubble column is analyzed in the present work.The presence of these surfactants increased the gas-liquid interfacial area,and decreased the liquid phase mass transfer coefficient,but with significant different extent.The results indicated that the CMC can be a key parameter affecting the mass transfer of CO_2 absorption into a dilute aqueous solution of a surfactant.Sardeing's model was used to fit the experimental data successfully by re-correlating the parameters.

Study on Optimization of Polymer Enhanced Foam Formulation System

Taking the pilot test area of polymer enhanced foam flooding in Y oilfield as the prototype, a numerical core model was established, and the polymer enhanced foam formulation system was optimized by analyzing the resistance factor and the change rule of oil recovery of different formulation systems. Research shows that the higher the polymer concentration, the greater the resistance factor, and the more obvious the sealing effect formed in the formation. The concentration of surfactant has a greater impact on the resistance factor. With the increase of surfactant concentration, the resistance factor increases significantly, and the plugging effect of foam agent on core is significantly enhanced. With the increase of gas-liquid ratio, the resistance factor first increases and then decreases. When the gas-liquid ratio is 1:1, the resistance is the largest, and the foam agent has the strongest plugging effect on the core. The optimal formula system of polymer enhanced foam flooding in Y oilfield is: polymer concentration is 1200 mg/L, surfactant concentration is 0.25 wt%, gas-liquid ratio is 1:1.

Surface nanobubbles on the hydrophobic surface and their implication to flotation

Nanobubbles play a potential role in the application of the flotation of fine particles.In this work,the identification of nanoentities was performed with a contact mode atomic force microscope(AFM).Moreover,the influences of setpoint ratio and amplitude of the cantilever and the responses of the formed surface nanobubbles to the fluctuation of pH,salt concentration,and surfactant concentration in the slurry were respectively studied.Nanobubbles were reported on the highly oriented pyrolytic graphite(HOPG)surface as the HOPG was immersed in de-ionized water under ambient temperature.The coalescence of nanobubbles occurred under contact mode,which provides strong evidence of the gaseous nature of these nanostructures on HOPG.The measuring height of the surface nanobubbles decreased with the setpoint ratio.The changes in the pH and concentration of methyl isobutyl carbinol(MIBC)show a negligible influence on the lateral size and height of the preex-isting surface nanobubbles.The addition of LiCl results in a negligible change of the lateral size;however,an obvious change is noticed in the height of surface nanobubbles.The results are expected to provide a valuable reference in understanding the properties of surface nanobubbles and in the design of nanobubble-assisted flotation processes.

Effects of surfactants on enzyme-containing reversed micellar system

With the development of colloid interface and enzyme technologies,enzyme-containing reversed micellar system has been receiving much attention in bioseparation and bioconversion. Because of its high efficiency,it has brought new opportunities for the development of molecular biotechnology. Reversed micelles represent nano-sized aqueous droplets stabilized by surfactant amphiphiles inside the bulk organic solvents. The entrapped enzymes have enhanced activities under those conditions as suited in the lipid bilayers of biological membranes. The fundamentals of enzyme-containing reversed micellar system are described in this paper,with special emphasis on the effects of surfactants varying in concentrations and structures. The latest study progress on the surfactants application in enzyme-containing reversed micelles is reviewed. The introduction of novel functional surfactants in micellar enzymology and their future development are also discussed.

Hydrophobic terminal group of surfactant initiating micellization as revealed by^1H NMR spectroscopy

The critical aggregation concentration（CAC） of four with three kinds of conventional surfactants, namely,two cationic surfactants [hexadecyltrimethyl ammonium bromide（CTAB） and tetradecyltrimethyl ammonium bromide（TTAB）], one anionic surfactant [sodium dodecyl sulfate（SDS）], and a nonionic surfactant [Triton X-100（TX-100）], were determined by variation of ^1H chemical shifts with surfactant concentrations. Results show that the CAC values of protons at different positions of the same molecule are different, and those of the terminal methyl protons are the lowest, respectively, which suggests that the terminal groups of the alkyl chains aggregates first during micellization. Measurement of the transverse relaxation time（T2） of different protons in SDS also show that the terminal methyl protons start to decrease with the increase in concentration first, which supports the above mentioned tendency.

Supplement and optimization of classical capillary number experimental curve for enhanced oil recovery by combination flooding

In the middle of the last century,American scientists put forward the concept of capillary number and obtained the relation curve between capillary number and residual oil through experiments.They revealed that the corresponding residual oil saturation decreased with increasing of capillary number;after capillary number reached up to a limit,residual oil saturation would become stable and did not decrease.These important achievements laid a theoretical base for enhanced oil recovery with chemical flooding.On the basis of the theory,scholars developed chemical flooding numerical simulation software UTCHEM.During the numerical simulation study of combination flooding,the authors found that as the capillary number is higher than the limit capillary number,the changes of the residual oil saturation along with the capillary number differ from the classical capillary number curve.Oil displacement experiments prove that there are defects in classic capillary number experimental curve and it is necessary to mend and improve.Capillary number‘calculation’curve is obtained with a method of numerical simulation calculation and a complete description of capillary number curve is provided;On this basis,combination flooding capillary number experimental curve QL is obtained through experiments,which is different from the classical capillary curve;and based on which,an expression of corresponding combination flooding relative permeability curve QL is given and the corresponding relative permeability parameters are determined with experiments.Further oil displacement experiment research recognizes the cause of the singular changes of the capillary number curve."Combination flooding capillary number experimental curve QL"and"combination flooding relative permeability curve QL"are written in combination flooding software IMCFS,providing an effective technical support for the application of combination flooding technical research.