Synthetic-based aphrons: Correlation between properties and filtrate reduction performance

Aphrons fluids, because of their “noninvasive” characteristic, are indicated for drilling zones that have multiple intercalations of depleted formations adjacent to formations that require high-density fluids. Aphrons are colloidal dispersions containing microbubbles, with cores of gas, liquid or emulsion ranging from 10 to 100 μm in diameter, that are highly stable due to their high interfacial area and multiple surrounding surfactant layers. This paper presents results of physical–chemical properties, bubble size distribution and filtration of systems containing microbubbles. The aphrons were generated by applying a pressure differential under a high-pressure high-temperature (HPHT) filtration cell. Tests were also run with different types of surfactants, specific for generation of bubbles in an organic medium (ester). The surfactants were analyzed for their surface tension and the dispersions produced were photographed under an optical microscope at 60× magnification. The images obtained were digitized to enable determination of the bubble size distribution using an ImageJ program. The filtrate reduction performance of these fluids was determined by static filtration in synthetic porous media. There was a correlation between the filtration characteristics of the fluids, the bubble size distribution and number of bubbles produced in each base and for each surfactant tested. The results obtained served as a reference to formulate a light, non-water-based drilling fluid containing microbubbles with “noninvasive” characteristics.     

Experimental Investigation of Rheological and Morphological Properties of Water in Crude Oil Emulsions Stabilized by a Lipophilic Surfactant

Rheological behavior of two crude oils and their surfactant-stabilized emulsions with initial droplet sizes ranging from 0.5 to 75 µm were investigated at various temperatures under steady and dynamic shear testing conditions. In order to evaluate the morphology and Stability of emulsions, microscopic analysis was carried out over three months and average diameter and size distribution of dispersed droplets were determined. The water content and surfactant concentration ranged from 10 to 60% vol/vol and 0.1 to 10% wt/vol, respectively. The results indicated that the rheological properties and the physical structure and stability of emulsions were significantly influenced by the water content and surfactant concentration. The crude oils behaved as Newtonian fluids over a wide range of shear rates, whereas the emulsions behaved as non-Newtonian fluids, indicating shear-thinning effects over the entire range of shear rates. The viscosity, storage modulus and degree of elasticity were found to be significantly increased with the increase in water content and surfactant concentration. The maximum viscosity was observed at the point close to the phase inversion point where the emulsion system changes from water-in-oil emulsion to oil-in-water emulsion. The results also indicated that the rheological properties of crude oils and their emulsions are significantly temperature-dependent.     

CFD Simulation of Rheological Model Effect on Cuttings Transport

Foam, as a non-Newtonian fluid, plays an important role in the underbalanced drilling technique in oil field development. The rheological properties of drilling fluids, such as foam, have a direct effect on flow characteristics and hydraulic performance. Two rheological models—the Herschel–Bulkley model and power law—were fitted to two foam systems in this study. Computational fluid dynamics (CFD) was used to simulate the effect of the rheological models on solid–liquid (cuttings transport) hydraulics in concentric and eccentric annulus during the foam drilling operation. The simulation results are compared to the experimental data from previous studies. The results of CFD using the power law model are in good agreement with experimental results in horizontal annulus with respect to the Herschel–Bulkley model with relative error less than 8%. Thus, for CFD cuttings transport for simulations in inclined and horizontal annulus, it is best to use the power law's rheological model parameters.     

Aphron applications — A review of recent and current research

Colloidal aphrons are multi-layered stable bubbles (CGAs) or droplets (CLAs), surrounded by a thin surfactant film. The small size of the aphrons creates a system with a high interfacial area which can be pumped like water without collapsing. The high stability of colloidal aphrons due to a thin soapy shell surrounding the core, and high interfacial area make them of interest in many processes such as mineral processing, protein recovery, drilling fluids, separation of organic dyes from waste water, predispersed solvent extraction of dilute streams, clarification and purification of suspensions, soil remediation, material synthesis and immobilization of enzymes. This article aims to provide a comprehensive database in generation, characterization and applications of colloidal gas and liquid aphrons from more than 140 published works so far. The article also reports scale up, industrial applications, technical limitation regarding aphrons application and important future research scopes.     

An Experimental Study of Influence of Salt Concentration,Mixing Time,and pH on the Rheological Properties of Pre-Hydrated Bentonite Slurries Treated by Polymers

The aim of this study is to investigate the influence of pH between 8.5 and 12.5, mixing time, and of NaCl, KCl, and CaCl₂ concentration over the range of 0% to 20% on the rheological properties of pre-hydrated bentonite slurry following by treatments with different polymers. Viscometric data gathered by viscometer described well by the Herschel-Bulkley rheological model for all fluids tested. Increasing salt concentration and pH led to some significant changes in the rheological properties. Moreover, adding saturated salt to pre-hydrated slurry resulted in increasing shear stress and plastic viscosity for all fluids.     

Multi-Walled Carbon Nanotubes as a Cosurfactant for Highly Concentrated Emulsions

The role of multi-wall carbon nanotubes (MWCNT) as a solid surfactant in highly concentrated water-in-oil emulsions was investigated. MWCNT were dispersed in the oil phase. These suspensions are viscoplastic fluids with the yield stress increasing by more than 1000 times with addition of 2% MWCNT, which demonstrates intensive “structurizing” ability. After emulsion preparation, MWCNT were concentrated at the interface, stabilizing emulsions. The dependence of the inversion point on MWCNT concentration was found. Emulsions containing up to 94 wt% of the aqueous phase can be prepared only when MWCNT is combined with conventional surfactant. Rheological properties of such compositions were measured. It was established that emulsions stabilized by a combined surfactant were more stable in comparison to conventional surfactant stabilized emulsion.     

Minimum Evaporation Model of Dermatological Delivery Systems. Lamellar Liquid Crystal Formulations Containing Brazilian Nut (Bertholletia excelsa HBK) Vegetable Oil and Guarana Glycolic Extract

Formulations with lyotropic liquid crystals were prepared from a Brazilian nut vegetable oil, guarana extract and combination of sorbitan monooleate (Span 80) and sorbitan monolaurate ethoxylate EO 20 (Tween 20) in the ratio 1:3 (surfactant component) and their physical–chemical aspects and rheological properties were determined. Compositions with liquid crystals were found in the pseudoternary diagram in a surfactant range of 70–90% and polarized light microscopy, small-angle x-ray scattering (SAXS) showed them to be lamellar. The preparations were furthermore characterized rheologically by shear stress shear rate sweeps finding plastic and pseudoplastic behavior without thixotropy. Electric conductivity and pH measurements demonstrated a potential for future application as dermatological delivery system of the active compounds in the Bertholletia excelsa and Paullinia cupana.      

Semi-Solid o/w Emulsions Based on Sucrose Stearates: Influence of Oil and Surfactant Type on Morphology and Rheological Properties

Sucrose stearate blends of intermediate lipophilicity are mild surfactants with thermosensitive gelling behavior. Binary systems and emulsions with sucrose stearate S-970 or S-1170 were developed and investigated by thermoanalytical and rheological measurements. The presence of an oil phase promoted the gelling potential of the esters especially at higher production temperatures. Semi-solid emulsions with viscoelastic properties comparable to weak gels were obtained with different dermatologically acceptable oils. The complex internal structure as visualized by fluorescence microscopy exhibited changes during storage in dependence of oil and surfactant type. A combination of S-970 with cetearyl ethylhexanoate-based oil phases led to superior physical stability.     

Limitations and Applicability of the Interfacial Shear Rheology in the Study of Monolayer Films at the Air-Water Interface

This article studies the applicability of a new technique in determining the interfacial shear rheology properties of surface active compounds relevant to the petroleum industry. It presents the theory behind the determination of the rheological parameters and the results of tests performed on a set of petroleum related compounds (asphaltenes, tetra-acid model compound, fatty acid, and surfactant). It is concluded that this technique is not mature enough to determine the properties of the studied compounds.     

Effects of Modified Sodium Lignosulfonate on Rheological Properties of Coal–Water Slurry with Low-Rank Coal

Coal–water slurry (CWS) is a new type of oil-replaceable liquid fuel with low pollution. The cost of CWS preparation will be greatly reduced if low-rank coal is used as the preparation material. In this work, chemical modification was used to prepare the modified sodium lignosulfonate (SL-M) hyper-dispersant, having larger molecular weight and more sulfonic groups than sodium lignosulfonate (SL), which was widely used for preparation of CWS from low-rank Shenhua coal due to its rich source and lower price. Effects of preparation conditions and molecular structure of SL-M on rheological properties of CWS were studied by using Haak rheometer. Results showed that the CWS transfered from viscous fluid to swelling fluid when the coal particle size decreased. The consistency coefficient of CWS decreased with the increase of additive dosage. The rheological properties of CWS became much better with the addition of the stabilizer, sodium carboxymethyl cellulose (CMC), compared with that of CWS without CMC. The prepared CWS changed from yield viscous fluid into yield swelling fluid with the increase of the molecular weight of SL-M. The rheological index was lower than 1 when the sulfonic group content was low, then it was increased with the increase of the sulfonic group content.     

Characterization of Optical Properties in Water-in-Oil Emulsion

There have been few studies on the factors that determine the overall appearance of emulsions. Optical properties are quite important in determining the perceived quality of emulsion-based products. The overall appearance of an emulsion is determined by the way that it interacts with electromagnetic radiation in the visible region of the spectrum, for example, reflection, transmission, adsorption, and scattering. These interactions are principally determined by the characteristics of emulsion droplets (size, concentration, and refractive index). The present study aims at characterizing the optical properties and rheological behaviors of water-in-oil emulsions, especially macroemulsions. There is a decrease in the absorbance spectra as increasing glycerin ratio in aqueous phase because the difference of refractive index between oil phase and aqueous phase decreased, which improved the transparency of water-in-oil emulsion. The absorbance of linear and branched surfactant emulsions were smaller than that of alkyl modified branched surfactant emulsion. Moreover the transparency of emulsions prepared with linear and branched surfactants was much clearer than that of alkyl modified branched surfactant emulsion. The absorbance spectra also showed that low polar oil attributed to the more transparent emulsion, compared with high polar or nonpolar oil. However, these kinds of oils were not helpful to prepare transparent emulsion because the appearance of these emulsions was translucent or opaque, even if polyols in aqueous phase was 30 wt%.     

A Study of the Influence of Nanoparticles on the Properties of Drilling Fluids

The effect of nanoparticles with different compositions and sizes on the rheological properties, filtration losses, and lubricating ability of drilling fluids has been experimentally studied. Nanoparticles of silicon, aluminum, and titanium oxides have been examined, while an aqueous bentonite suspension with a solid phase mass fraction of 5% has been used as a basic model of a drilling fluid. The concentrations and sizes of nanoparticles in the drilling fluids have been varied from 0.25 to 2 wt % and from 5 to 100 nm, respectively. It has been shown that the addition of nanoparticles substantially changes the properties of the drilling fluids. In contrast to suspensions of particles with macro- and microscopic sizes, the rheological parameters, filtration losses, and lubricating and sticking abilities of the suspensions containing nanoparticles depend on the size and nature of the latter and vary markedly already at low nanoparticle concentrations.     

Influence of Surface-Active Compounds on Starch Dispersion in Water. Part I. Starch Pasting

The influence of native lipids and additives of surface-active compounds on starch paste rheology was investigated. The aim of the study was to gain better understanding of mechanisms involved in starch gelatinization and how these structure changes of granules later affect rheological properties of pastes and gels. Starches from three main sources—potato, maize, and wheat—were tested; sodium dodecylsulfate, oleate, and benzalkonium chloride were employed as additives. Starch pasting was examined by a rheometer to get a viscosity profile, also pastes were analyzed by differential scanning calorimetry, for particle size using a light scattering technique. Results revealed that there was a competition between native lipids and added surfactants for amylose complexation. Complexes formed during gelatinization were strongly affecting granule swelling and dissolution of starch polymers, and viscosity of pastes was mainly dependent on the particle size of a disperse phase in the paste. Addition of strong ionic surfactants to cereal starches resulted in smaller granular remnants and, therefore, decreased viscosity, while the weak anionic surfactant promoted an increase in the particle size and paste viscosity for both cereal and tuber starches. The mechanism of the effect of surfactants on the particle size in pastes is discussed.     

Formation Mechanism of Zinc Oxalate Particles in the Internal Aqueous Droplets of Emulsion Liquid Membrane

We have investigated the formation and evolution of zinc oxalate particles in internal aqueous droplets and their effects of emulsion interface properties. The formation of particles follows an aggregation-controlled mechanism that depends on the size of droplets and surfactant. The size of droplets determines the final shape of the particles by affecting the supersaturation ratio to form rod-like and sheet-like particles. The surfactant adsorbed on the particles changes the wettability, leading to the aggregation of the primary particles at the internal water-oil interface. Moreover, the adsorption can cause a higher level of impurity and defects in as-synthesized particles. This effect could be directly employed to fabricate heterojunction rectifier.     

Investigation of Oil–Asphaltene Slurry Rheological Behavior

The presence of asphaltene means additional difficulties related to transport and processing due to the increased crude oil viscosity caused by the asphaltene. For a better knowledge of the flow properties of asphaltene containing crude oils, it is necessary to understand how asphaltene affects the rheological properties. The aim of this article is to provide information on such rheological properties of oil–asphaltene slurry systems. The results of rheological experiments show that the non-Newtonian flow curves can be approximated by the Bingham plastic model to determine the apparent viscosity and the yield stress as a function of asphaltene concentration and temperature. An explanation is also provided for the observed behavior.     

Investigations of the Effects of Salt and Biopolymer Ratio on Sodium Caseinate-Xanthan Interactions in Aqueous Solution and Emulsions

The aim of this work was to investigate interactions that can take place between, proteins and polysaccharides, in the presence of electrolytes. Thus, our objective was to study the influence of NaCl addition on the associative and/or segregative interactions in the case of biopolymer mixtures and fine emulsions stabilized by sodium caseinate, by analysis of the rheological properties and zeta potential. From the experimental results, it was shown that the presence of salt affects the rheological and physicochemical properties of the aqueous phase and consequently the emulsion stability. Indeed, the electrolytes can modify the conformation of proteins and polysaccharides, by electric neutralization of their charge, as they can generate a complex coacervation or increase their incompatibility.     

Effects of Salts Containing Mono-, Di-, and Trivalent Ions on Electrical and Rheological Properties of Oil-Water Interface in Presence of Cationic Surfactant: Importance in the Stability of Oil-in-Water Emulsions

Many industrial applications of oil-in-water emulsions involve salts containing ions of different valence. The properties of the oil-water interface (e.g., interfacial tension, zeta potential and interfacial shear viscosity) are strongly influenced by the presence of these salts. This work investigates the role of NaCl, CaCl₂ and AlCl₃ on these properties of the hexane-water interface in presence of a cationic surfactant, viz., hexadecyltrimethylammonium bromide. Addition of salt enhanced the adsorption of surfactant molecules at the hexane-water interface, which increased the interfacial charge density, and consequently, the zeta potential. Interfacial shear viscosity significantly decreased in the presence of salt. The effectiveness of salt at a given concentration was in the sequence: AlCl₃ > CaCl₂ > NaCl. The hexane-in-water emulsions coarsened with time due to the coalescence of hexane droplets. The increase in droplet size with time was analyzed by a model based on the frequency of rupture of the thin aqueous film. The rate constants for coalescence were determined. The rate of coalescence increased in presence of salt.      

Prediction of Rheological Properties of Multi-Component Dispersions by Using Artificial Neural Networks

This article shows the ability of artificial neural network (ANN) technology for predicting the correlation between rheological properties of multi-component food model systems and their chemical compositions. Multi-component food model systems were made of whey protein isolate (WPI) (2, 4 wt%), Iranian tragacanth gum (TG) (Astragalus gossypinus) (0.5, 1 wt%) and oleic acid (5, 10% v/v). The input parameters of the neural networks (NN) were these chemical compositions, namely WPI and TG concentrations, and oleic acid volume fractions. The output parameters of the NN models were rheological properties of multi-component food model systems (flow and consistency indices, viscosity, loss and storage moduli). Results showed that, ANN with training algorithm of back propagation (BP) was the best one for the creation of nonlinear mapping between input and output parameters. The best topology was 3-10-5. The ANN model predicted the rheological properties of multi-component food model systems with average RMSE 4.529 and average MAE 3.018. These results show that the ANN can potentially be used to estimate rheological parameters of multi-component food model systems from chemical composition. This development may have significant potential to improve product quality control and reduce time and costs by minimizing the rheological experiments.     

Rheological Behavior of Viscoelastic Wormlike Micelles in CTAB/SSS/H2O Systems

The effect of the addition of sodium 4-styrenesulfonate (SSS) and KNO3 as well as temperature and shear rate on the structural transition of aqueous micellar solutions of the cationic surfactant cetyl trimethyl ammonium bromide (CTAB) was studied by viscosity. The effect of hydrocarbons on viscoelastic CTAB solutions was also examined. Possible mechanism for formation of CTAB wormlike micelles in the presence of sodium 4-styrenesulfonate (SSS) and KNO3 was discussed. The rapid increase in the apparent viscosity of CTAB solutions on the addition of SSS and KNO3 was due to the transition in micellar shape from spheres to wormlike ones. The rheological properties of CTAB solutions fit Maxwell model at low shear frequency. AFM image indicated a structure of transient network of CTAB/SSS/KNO3/H2O solution.