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Due to extensive applications of microfluidic devices, manufacturing of these apparatus has recently been noticed. Production of multiple emulsions is one of the main goals of manufacturing microfluidic devices. Design and fabrication of microfluidics are functions of the size of emulsion droplets, properties of fluids applied for emulsification, and considered stability for emulsions. In this article, we have manufactured a novel microfluidic device using simple fabrication and accessible materials. Capillary tubes, PTFE (polytetrafluoroethylene) chassis, a medical needle of gauge 32, and O-rings are the primary materials used to produce this device. The production procedure is explained completely, and all the drawings are represented. Concerning probable interactions between glues and flowing fluids, we tried to fabricate and seal the device without applying chemical agents. The device is tested by n-heptane and deionized water to produce multiple water-in-oil-in-water (W/O/W) emulsions. A sensitivity analysis on the rate of injection is performed. Considering the HLB (hydrophilic–lipophilic balance) as an important property of emulsifiers, the effects of two different types of emulsifiers (sodium dodecyl sulfate with HLB of 40 and glycerol monostearate with HLB of 3.8) at various concentrations are investigated. Due to the results, the injection rate of the mediate phase should be less than half of the outer phase for the formation of emulsions. Consequently, the rate of injection for the inner phase should be less than half of that for the mediate phase. The simplicity of production and accessible raw materials could be considered as the strengths of our microfluidic device. [ABSTRACT FROM AUTHOR]

Reservoir heterogeneity is an important factor which should be considered for each operation in oilfields. Acidizing operation is performed to eliminate or reduce the damages of reservoirs. The dissolution of the minerals and rock texture in damaged areas is the main goal of acidizing. However, the existence of high permeable zones through flowing paths results in extra damages and fluid loss. Some additives could be added to the injected acid to avoid these undesirable phenomena. In this research, we added a Zwitterionic sulfonate surfactant to hydrochloric acid (HCl) solution and evaluated the rheological behavior of several compositions of acid‐based viscoelastic surfactant (VES) solutions under various temperature and shear rates. The capability of optimum solution to plug the high permeable zone and divert the acid flow to low permeable zone is examined. The optimum solution was injected into a parallel sandpacked system with different permeabilities at various flow rates (1, 3 and 5 cc/min). It was observed that the injection rate of 3 cc/min has the most efficiency to reduce the heterogeneity. Besides the tendency of VES based solutions for altering wettability of rock to more water‐wet condition is observed. The findings of this study can help the better understanding of practical application of VES in acidizing through heterogeneous reservoirs. Besides, effective parameters for such application are determined. [ABSTRACT FROM AUTHOR]

In this work, the efficiency of CO2-foam injection for enhanced oil recovery (EOR) is investigated. Six floods were performed on sand pack columns. Pure water injection, WAG injection and simultaneous injection of CO2 and surfactant solution with various concentrations were conducted. Notable difference was observed between oil production in secondary surfactant assisted WAG and other injection scenarios. The experimental work in this research shows that increase in concentration of surfactant in the injection process results in mobilization of more oil that may not have been achievable by using water flooding and WAG flooding methods individually. [ABSTRACT FROM AUTHOR]

In this study, inverse emulsion polymerization (IEP) of acrylamide (AAm) and 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) was conducted with a constant monomer AAm/AMPS feed ratio of 80%:20%. The effects of important reaction parameters on monomer conversion, intrinsic viscosity and molecular weight of nanostructured polymers (NSPs) were comprehensively assessed and the optimal synthesis conditions (in terms of the high molecular weight characteristics) was obtained using Box–Behnken design (BBD) combined with response surface methodology (RSM). The glass transition temperature (Tg) of the synthesized NSP was obtained at 165 °C by differential scanning calorimetry (DSC). The rheology measurements demonstrated the long–term stability of the synthetized NSPs after 50 days of aging at 90 °C within the 87,000 ppm brine. Regarding the high molecular weight and acceptable long–term stability at elevated temperatures and salinity levels, the synthesized NSP could be considered as potential candidates for enhanced oil recovery (EOR) applications under harsh condition reservoirs. [ABSTRACT FROM AUTHOR]

Drillpipe eccentricity is a common issue in horizontal drilling operations. The eccentricity is a non-manipulative parameter by itself but its impact is a function of various parameters such as rate of penetration (ROP), fluid flow rate (Q), cuttings bed height, wellbore path and drillpipe rotation. The goal of this study is to observe the cutting's accumulation in different eccentric annuluses by employing a multiphase Eulerian flow model including a Herschel-Bulkley drilling fluid. Turbulence was implemented using Reynolds Stress Model which reveals proper results, especially on asymmetric and complex cases. All of these are developed and calculated through a comprehensive Computational Fluid Dynamics (CFD) simulations to solve the governing equations in the multiphase medium. A sensitivity analyzes were implemented from concentric to 75% eccentric cases accompanying different variations of fluid flow rate, ROP, and drillpipe rotation. The results demonstrated that further eccentricity from a certain amount will abruptly increase the cutting's accumulation which is a function of bed height, ROP/Q, and drillpipe rotation. However, rotation's impact is negligible above a certain speed of rotation after which the sudden increase of cutting's accumulation caused by eccentricity is not observable. [ABSTRACT FROM AUTHOR]

Colloidal silica nanoparticles with average diameters less than 100 nm were made using a modified Stöber method involving tetraethylorthosilicate (TEOS) and octadecyl trimethoxysilane (OTMOS) as a surface modifier. We show that the hydrophobicity of the nanoparticles could be tuned in this one-step reaction by introducing methanol as a co-solvent with ethanol and optimizing the ammonium hydroxide concentration and time elapsed between TEOS and OTMOS addition. Using this approach, silica nanoparticles could be made directly with the proper surface hydrophobicity to stabilize invert (water-in-oil) emulsions with shear-thinning rheological behavior as needed in oil drilling applications. Particle characterization data from transmission and scanning electron microscopy (TEM and SEM), Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), and contact angle measurements are presented. [ABSTRACT FROM AUTHOR]

An oil-based drilling fluid should be stable and tolerant to high temperatures for use in deep drilling. An invert emulsion of water in oil is a good choice as an oil-based drilling fluid which is a mixture of a solid phase and two immiscible liquid phases stabilized by a polymeric surfactant. In deep drilling, due to high temperatures, the polymeric surfactant degrades and a phase separation occurs. Here, octadecyltrimethoxysilane-modified silica nanoparticles were used to form a stable invert emulsion of water in oil for the drilling fluid model which resulted in a milky fluid with the formation of 60 µm water droplets. In addition, rheological study showed that using hydrophobic silica nanoparticles resulted in a stable water in oil invert emulsion with desired properties for a drilling fluid that can be modified by adjusting the nanoparticle nature and content. Aging experiments at 120 °C indicated that they also have good stability at high temperatures for challenging drilling operations. [ABSTRACT FROM AUTHOR]

The size and morphology of asphaltene aggregates, precipitated from live oil by pressure depletion at the reservoir temperature was studied using scanning electron microscopy and atomic force microscopy. The experimental studies showed that the mean size of aggregates increased when pressure decreased. The results indicate that the morphology of aggregates was changed from amorphous spherical and elliptical shapes to irregular. A bimodal distribution function was able to describe the size distribution in pressure range of 500 to 3500 psi. At higher pressure, the unimodel was able to represent the size distribution. The results showed reduction in live oil stability and asphaltene aggregation with pressure drop. [ABSTRACT FROM AUTHOR]

Granulation of nitrifying bacteria was investigated in a continuous bubble column bioreactor. Then, the combined effect of aeration and ammonium loading rates on dissolved oxygen (DO) concentration as well as nitrification process was evaluated in the system using an experimental design technique. After 120 days, stable nitrifying granules with average diameter of 1.4 mm and settling velocities of 55 m/h were obtained. The influence of increasing ammonium loading rate (ALR) was found to be more significant than decreasing aeration rate on the reduction of DO concentration inside the nitrifying bioreactor. The system could handle the ALR values of 0.48-1.92 gNH4+-N/L d with the ammonium removal efficiency from 65% to nearly 100% at the tested airflow rates of 2.5 and 4.5 L/min. At the low aeration, the complete ammonium conversion to nitrate was replaced with nitrite when the ALR increased to 1.44 gNH4+-N/L d. At the high aeration, however, almost complete nitrification was achieved except the high ALR in which the nitrite accumulation was observed up to 38%. The study demonstrated that the continuous bioreactor had a considerable performance for obtaining stable nitrifying granules to have nitrite accumulation under control with changing the ratio of aeration rate and ALR. [ABSTRACT FROM AUTHOR]

Growing oil prices coupled with large amounts of residual oil after operating common enhanced oil recovery methods has made using methods with higher operational cost economically feasible. Nitrogen is one of the gases used in both miscible and immiscible gas injection process in oil reservoir. In heterogeneous formations gas tends to breakthrough early in production wells due to overriding, fingering and channeling. Surfactant alternating gas (SAG) injection is one of the methods commonly used to decrease this problem. Foam which is formed on the contact of nitrogen and surfactant increases viscosity of injected gas. This increases the oil-gas contact and sweep efficiency, although adsorption of surfactant on rock surface can causes difficulties and increases costs of process. Many parameters must be considered in design of SAG process. One of the most important parameters is SAG ratio that should be in optimum value to improve the flooding efficiency. In this study, initially the concentration of surfactant was optimized due to minimization of adsorption on rock surface which results in lower cost of surfactant. So, different sodium dodecyl sulfate (SDS) concentrations of 100, 500, 1000, 2000, 3000 and 4000 ppm were used to obtain the optimum concentration at 70 °C and 144.74 x 105 Pa. A simple, clean and relatively fast spectrophotometric method was used for determination of surfactant which is based on the formation of an ion-pair. Then the effect of surfactant to gas volume ratio on oil recovery in secondary oil recovery process during execution of immiscible surfactant alternating gas injection was examined experimentally. The experiments were performed with sand pack under certain temperature, pressure and constant rate. Experiments were performed with surfactant to gas ratio of 1:1, 1:2, 1:3, 2:1 and 3:1 and 1.2 pore volume injected. Then, comparisons were made between obtained results (SAG) with water flooding, gas flooding and water alternating gas (WAG) processes. This study shows that using the concentration of 1500 ppm of surfactant solution is practical and economical. Results also show that the SAG ratio of 1:1 with 0.2 cm³/min at temperature and pressure of 70 °C and 144.74 x 105 Pa, has the maximum oil removal efficiency. In this SAG ratio, stable foam was formed and viscous fingering delayed in comparison to other ratios. Finally, the results demonstrated that SAG injection has higher oil recovery in comparison to other displacement methods (water flooding, gas flooding and WAG). [ABSTRACT FROM AUTHOR]