A trend in the global technological progress in the last few decades is the development of microsystem technology, microelectromechanical systems and corresponding technologies. Fluid mixing is an extremely important process widely used in various microfluidic devices (chemical microreactors, chemical and biological analyzers, drug delivery systems, etc.). To increase the mixing rate, it is necessary to use special devices: micromixers. This paper presents the results of a hydrodynamic simulation of Y-shaped micromixers. Flows are analyzed for both low and moderate Reynolds numbers. The passive and active mixers are considered. The dependence of the mixing efficiency on the Reynolds and Péclet numbers, as well as the possibility of using the hydrophobic and ultra-hydrophobic coatings is analyzed. Five different flow regimes were identified: (1) stationary vortex-free flow (Re < 5); (2) stationary symmetric vortex flow with two horseshoe vortices (5 < Re < 150); (3) stationary asymmetric vortex flow (150 < Re < 240); (4) non-stationary periodic flow (240 < Re < 400); and (5) stochastic flow (Re > 400). The maximum mixing efficiency was obtained for stationary asymmetric vortex flow.

The systematic experimental investigation of the viscosity of more than 30 different nanofluids was carried out. The investigated nanofluids were prepared based on distilled water, ethylene glycol and engine oil containing nanoparticles Al₂O₃, TiO₂, ZrO₂, CuO, Fe₂O₃, and Fe₃O₄, as well as nanodiamonds. The nanoparticle volume concentration ranged from 0.25 to 8%. The size of nanoparticles varied from 5 to 150 nm. The temperature changed from 25 to 60 °C. The effect of the nanoparticle concentration and size, as well as the base liquid properties, temperature, and additives of stabilizing surfactants on the viscosity of nanofluids were investigated. In particular, the factors affecting the rheology of nanofluids were studied. It was found that the viscosity of nanofluids depends on the material of the nanoparticles. It is shown that with decreasing nanoparticle size, the viscosity of nanofluids increases. In contrast to the classical microscopic suspensions, the relative viscosity of nanofluid depends on the viscosity of the base liquid. In general, the higher is the viscosity of the base fluid, the higher is the increment of the nanofluid viscosity. It was found, that the rheological behavior of the Newtonian nanofluid can become non-Newtonian with the growth of the volume fraction of nanoparticles and decrease of their size. At very high nanoparticle concentration the relative viscosity of nanofluid depends on temperature and characterized by hysteresis, i.e. the viscosity of nanofluid during heating and cooling differs significantly.

The unique properties of supercritical fluid technology have found wide application in various industry sectors. Supercritical fluids allow for the obtainment of new types of products with special characteristics, or development and design of technological processes that are cost-effective and friendly to the environment. One of the promising areas where supercritical fluids, especially carbon dioxide, can be used is the oil industry. In this regard, the present review article summarizes the results of theoretical and experimental studies of the use of supercritical fluids in the oil and gas industry for supercritical extraction in the course of oil refining, increasing oil recovery in the production of heavy oil, hydraulic fracturing, as well as processing and disposal of oil sludge and asphaltenes. At the end of the present review, the issue of the impact of supercritical fluid on the corrosion of oil and gas equipment is considered. It is found that supercritical fluid technologies are very promising for the oil industry, but supercritical fluids also have disadvantages, such as expansion or incompatibility with materials (for example, rubber).

Global estimates for our remaining capacity to exploit developed oil fields indicate that the currently recoverable oil (light oil) will last for approximately 50 years. This necessitates the development of viscous and superviscous oil fields, which will further compensate for the loss of easily produced oil. In situ combustion is the most promising production method, which allows for increased oil recovery from a reservoir. This being the case, this study provides an overview of global trends regarding the research and implementation of the method under consideration, in order to promote understanding of its applicability and effectiveness. The background to the development of the method is discussed in detail, illustrating the growing interest of researchers in its study. Cases of both successful as well as inefficient implementations of this method in real oil fields are considered. The main focus of the article is to investigate the influence of the parent rock and catalysts on the combustion process, as this is a new and actively developing area in the study of enhanced oil recovery using in situ combustion. Geological surveys, in addition to experimental and numerical studies, are considered to be the main methods that are used to investigate processes during in situ combustion. The analysis that we carried out led us to understand that the processes which occur during the combustion of heavy oil are practically unpredictable and, therefore, poorly understood. The specificity of the oil composition under consideration depends on the field, which can lead to a change in the required temperature regimes for its production. This indicates that there exists multiple specific applications for the method under consideration, each requiring additional full studies into both the fractional composition of oil and its reservoirs. The article also considers various technologies for implementing the in situ combustion method, such as ND-ISC, THAITM, COSH, CAGD, and SAGD. However, the literature review has shown that none of the technologies presented is widely used, due to the lack of an evidence base for their successful application in the field. Moreover, it should be noted that this method has no limits associated with the oil occurrence depth. This technology can be implemented in thin reservoirs, as well as in flooded, clayey, sandy, and carbonate reservoirs. The review we have presented can be considered as a guide for further research into the development of global solutions for using the proposed method.

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....

The integrated effect on homogeneous and heterophase liquids that can be used for technological purposes has drawn the attention of researchers in various sciences. Cavitation impact on oil is among the efficient methods of intensifying chemical–technological, hydromechanical, and mass-exchange processes and the destruction of substances. This work reviews in detail and analyzes the mechanisms of impact and application of cavitation in various processes in the petroleum industry, including the refining processes, that are associated with crude oil and petroleum waste, such as reduction of viscosity, demulsification, desulfurization, and improvement of quality of heavy oil and petroleum refinery products, including oil sludge and waste oil-containing water.