Annotation of the results obtained in 2019
The research objective carried out by the team this year was a comprehensive and systematic study of the efficiency of oil displacement using nanosuspensions and nanoemulsions. As a result of investigate, formulations of solutions based on nanoemulsions, nanosuspensions and polymer compositions for oil displacement from the reservoir were developed, systematic experimental data on the rheological characteristics of nanosuspensions and nanoemulsions were obtained, their effect on interfacial tension and wettability at the oil and rock interface was studied, experimental and numerical data on the characteristics of oil displacement from rocks using nanoemulsions and nanosuspensions were obtained. As a result, the following main results were obtained in this part of the project. 1. Technologies for obtaining stable nanosuspensions and low-concentration nanoemulsions for reservoir flooding have been developed, which allow obtaining colloid-resistant suspensions and emulsions with droplet sizes of about 100 μm, the main properties of which change slightly for at least ten days. 2. A systematic study of the properties of more than 40 different solutions based on nanoemulsions, nanosuspensions and polymer compositions for the oil displacement from the reservoir was carried out. As opposed to previous studies, this project for the first time obtained systematic data on the volumetric (second) viscosity of aqueous nanosuspension. It was shown that the shear viscosity of nanosuspensions substantially depends on the size of the nanoparticles. The viscosity coefficient of nanosuspension increases with a decrease of the nanoparticles size. The dependence of the viscosity of nanosuspension on the material of nanoparticles was experimentally shown. Moreover, for the first time in this project, it was experimentally shown that the effect of the nanoparticle material on the viscosity of nanosuspensions decreases with an increase in the nanoparticles size. .During the course of the project, the effect of the volumetric content and type of base oil in the emulsion, the type and concentration of emulsifier, temperature and duration of ultrasonic treatment on the properties of the emulsion was studied. The relationship between the size of the droplets in emulsions with their properties was established. As a result, the necessary reagents were selected and their optimal concentrations were determined, a technology for the preparation of emulsions with high colloidal stability and temperature stability was developed. 3. It was shown that the wettability characteristics of water-oil systems are significantly affected by the presence of nanoparticles. The interfacial tension at the oil / nanosuspension interface decreases with an increase in the nanoparticles concentration, and the contact angle for an oil drop on a rock in nanosuspension, on the contrary, increases. In addition, it was shown that this effect depends on the nanoparticles size. The contact angle at the oil / nanosuspension / rock interface increases with a decrease in the nanoparticles size,, and the oil / nanosuspension interfacial tension coefficient, on the contrary, decreases. The effect of the addition of nanoparticles on the wettability of a rock surface by oil in nanosuspension substantially depends on the material of the rock. An analysis of the literature shows that such systematic studies were performed for the first time. Thus, it was found that the use of nanosuspensions and nanoemulsions can radically change the wettability of rock oil, which can significantly increase the oil recovery factor. 4. It was experimentally established that the addition of nanoparticles allows to increase the oil recovery factor. Moreover, the oil recovery factor increases on average with an increase in the nanoparticles concentration in the displacement fluid. For the first time, the dependence of the oil recovery factor on the size of nanoparticles was systematically studied. As a result, it was found that the oil recovery factor increases with decreasing nanoparticle size. These data are in good agreement with measurements of the interfacial angle in oil / nanosuspension / rock systems. Systematic measurements performed for several nanosuspensions with a controlled nanoparticle size, for the first time allowed to detect the effect of nanoparticle material on oil recovery factor using nanosuspension. The effect of the initial core permeability on the oil recovery factor for nanosuspensions was studied. It was found that the effect of the addition of nanoparticles increases with an increase in permeability. 5. It was shown that nanoemulsions also have significant potential for increasing the oil recovery factor. The effect of the volume fraction of the dispersed hydrocarbon phase in the emulsion on the oil recovery factor was studied. It was shown that the oil recovery factor increases with an increase in the content of the hydrocarbon phase. So, in particular, for nanoemulsions with an oil content of 2.5 vol.% the oil recovery factor was increased by almost 40%. At the same time, a significant effect was observed even at an oil concentration starting from 1%. In our opinion, it makes this emulsion very attractive for reservoir flooding. Currently, the experience of using heavy oil fractions for injection into the reservoir during oil production is known. There are currently no studies on the use of low concentrated oil emulsions for these purposes. 6. The results of a numerical study of oil displacement processes using nanofluids were obtained. Using simulation a systematic study of factors affecting the efficiency of the displacement process was carried out. The flow rate of the displacement fluid, the size of the nanoparticles, the viscosity of the oil, and the permeability of the rock were considered as such factors. An analysis of the obtained data allowed to explain the basic regularities of the influence of nanoemulsions and nanosuspensions on the process of oil displacement. It allowed possible to finally establish that the main reason for the increase in oil recovery factor during oil displacement by nanofluid is the improvement in the rock wetting. The results of numerical simulations were compared with experimental data. Good agreement was obtained at a qualitative level. 7. In general, based on the results of this part of the research it was demonstrated that the injection of nanoemulsions and nanosuspensions into the reservoir to increase oil recovery has great potential for use. There is a large reserve for improving these technologies by selecting the appropriate nanomaterials and chemicals, and developing technologies for their injection. 8. The analysis and systematization of the obtained data was carried out and practical recommendations on the use of nanosuspensions and nanoemulsions in the technologies for the development and operation of oil and gas fields were formulated on their basis. It was shown that the developed drilling fluids with nanoparticles have some fundamental advantages compared to traditional solutions: they have increased operational characteristics (working at high temperatures and pressure under the influence of aggressive environments, etc.); maximally adaptable to mining and geological conditions and development features; have a wide range of the properties control; the additive is required in a small amount, cost reduction is possible; environmentally inert. This provides a broad perspective on their application. The results demonstrated in the project on the possibility of controlling the properties of drilling fluids using nanoparticle additives exceed the world level in many respects and, in our opinion, could be successfully implemented in the domestic oil and gas industry. Of course, the research potential for the possibility of using nanoemulsions and nanosuspensions as oil displacement agents has great potential for implementation. It is well known that in recent decades the level of oil production at our major fields in Western Siberia, which account for more than 50% of the reserves, has been declining. The problem is compounded by low oil prices, which are unlikely to increase significantly in the foreseeable future. These conditions require the creation of fundamentally new highly effective technologies for the development of hydrocarbon deposits, which make profitable production in conditions of low oil prices. In the future, the widespread use of nanosuspensions and nanoemulsions for the development and operation of oil and gas wells could become one of these technologies. The results obtained in the project demonstrated that the injection of nanoemulsions and nanosuspensions into the reservoir to increase oil recovery has great potential for use. There is a large reserve for the improvement and refinement of these technologies by selecting the appropriate nanomaterials and chemicals, and developing technologies for their injection. Of course, the obtained results are only the first step towards the widespread introduction of this technology in the development of oil and gas fields. Further systematic research is required, including pilot studies. Nevertheless, there are undoubtedly prospects for using nanofluidic technologies to increase oil recovery. 9. Over the past period, in the project it was published 8 articles in peer-reviewed Russian and foreign scientific journals indexed in the WoS Core Collection and SCOPUS databases, including 2 publications in a journal Q1 (Journal of Natural Gas Science and Engineering, Journal of Natural Gas Science and Engineering). The project results were presented at six national and international conferences. In total, 10 reports were made by the project participants this year. In October 2019, the project team and under its auspices held the VIII All-Russian Scientific and Technical Conference with international participation, "ULTRA-DISPERSED POWDERS, NANOSTRUCTURES, MATERIALS" Krasnoyarsk, October 24-25, 2019, which was attended by more than 50 participants. 10. Thus, all the tasks planned in the project for this year have been completed and the necessary indicators have been achieved

 

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Annotation of the results obtained in 2017
Active interest to the suspensions with nanoparticles (nanofluids) appeared a quarter of a century ago and since then it has been continuously growing. The number of publications devoted to the study of nanofluids properties and applications is increasing exponentially. Owing to their small size, nanoparticles have a number of unusual properties that are absent in the macroscopic dispersed particles. Unusual properties of nanoparticles make the nonstandard properties of nanofluids, in which they are an integral part. This led to the widest range of nanofluids applications. Usage of nanofluids in the reservoir engineering and exploitation began much later. However, at present, range of nanofluids application is investigated very actively. Modern drilling muds have different properties, which can be influenced by nanoparticle additives at some point. Such properties include viscosity and rheology. The objective of the research carried out by the team in this year is a comprehensive and systematic analysis of the effect of nanoparticles additives with various sizes and compositions on the rheology, filtration, lubricity and flow characteristics of drilling muds in borehole. Over the past period, the drilling mud compositions have been developed and the properties of more than 40 different muds with nanoparticles additives were studied. The following results were obtained. 1. Viscosity and rheology have very important significance in the drilling muds application, since they effect on pressure loss during flushing of borehole, cutting transport efficiency, borehole stability and many other factors in drilling. Experimental study of the viscosity and rheology of the developed drilling muds with nanoparticles was carried out. It was found as a result, that the nanoparticles addition to drilling muds can significantly improve their rheological characteristics. It was suggested based on the analysis of the obtained data, that the rheology of drilling muds with nanoparticles is generally described by a power-law model at low concentrations of nanoparticles. As the nanoparticles concentration increases, the rheological properties of the suspension undergoe qualitative changes. The yield point appears in the drilling mud. Thus it was shown that it is possible to control the viscous and rheological properties of drilling muds by adding the nanoparticles. Significant effect of even very low concentrations of nanoparticles addition on the rheology of drilling muds was shown as a result. It was also shown, that the rheological properties of the suspensions depend on the size of nanoparticles too and this effect is enhanced during the decrease in the nanoparticles size. For another thing, it was found that the nanoparticles material also influences on the rheological characteristics of drilling muds. The dependence of viscosity and rheology on size and material is not usual for classical suspensions with microscopic particles, it is a distinctive feature of nanosuspensions. Thus, it was found that the nanoparticles addition affects the rheology of drilling muds, including, with a very high microparticles content. In this case, rheological parameters of nanosuspensions depend on the size and material of nanoparticles as distinct from suspensions with macro and microscopic particle sizes, which allows controlling the properties of muds in very wide ranges. For example, it was shown that the addition of 40 weight percent of microparticles to the drilling mud increases the effective viscosity for about 30% compared to the initial mud. On the other hand, as the 0.25 weight percent of silicon dioxide nanoparticles add, the effective viscosity of the drilling mud increases fourfold! 2. The most important characteristic of drilling muds is filterability. In the process of oil and gas well drilling, the drilling mud can penetrate into the rock through the borehole walls. This phenomenon is called filtration losses. In this case, the drilling mud loss occurs, which increases the cost of well construction. At the same time, the filtration losses of drilling mud in the bed are one of the main reasons for the cracking and the borehole instability. A variety of methods to borehole hardening are used to eliminate these phenomena. As a rule, various disperse (1-100 μm) fillers of drilling muds, which can penetrate into the rock and seal it, are used. A systematic experimental study of the effect of nanoparticles concentration, size and materials on the filtration properties of drilling muds was carried out for the first time in our project. It was shown as a result, that the nanoparticles addition to the drilling mud significantly affects the amount of filtration losses. It was found that as the 1-2 weight percent of nanoparticles add, the filtration losses of drilling mud reduce threefold for low permeable cores with 3 μm pore sizes. The influence of nanoparticles depends on both their concentration and size. It was shown that as the nanoparticles concentration increases or their size decreases the filtration losses decrease too. Electron microscopy showed that the main reason for filtration loss enhancement with nanoparticles addition to clay muds is a decrease of permeability of the filter cake that forms on the walls of the borehole. The filter cake of drilling mud consists of clay particles and microparticles that present in the mud. When the nanoparticles add to the drilling mud they able to fill the pores between the clay flakes and microparticles, thereby reducing the permeability of the cakes on the filter surface. 3. Another important characteristic of drilling muds is their lubricity. The use of muds with improved antifriction properties leads to a significant reduce of energy costs during the wells construction. A systematic experimental study of the antifriction properties of drilling muds with nanoparticles was carried out in this year. The influence of the concentration, size and material of the added nanoparticles on the friction coefficient of drilling muds during different friction modes was studied. As a result of systematic experiments it was found that the nanoparticles addition to drilling muds can lead to a significant improvement in their antifriction properties. In this case, such effect of reducing the friction coefficient increases with decreasing particle size and can reach 20-35% at very low concentrations. 4. Another serious complication of the drilling process caused by friction is the sticking of the drill pipe, characterized by the complete or partial stop of the drilling tool. This effect appears due to the adhesion of the drill pipe to the filter cake, which formed on the walls of borehole as a result of filtration. Therefore, when creating new drilling muds, much attention is paid to the sticking capacity and friction of the filter cake. The effects of the nanoparticles addition on the friction coefficient and the sticking capacity of the filter cakes were studied in this year. It was shown as a result that as the standard inclusions of microparticles add to the drilling mud, the friction coefficient of the filter cake increases four and a half times. As the nanoparticles add to these muds with microparticles the value of the friction coefficient of the filter cake is halved. Thus, it was found that the nanoparticles addition to drilling muds can significantly reduce the friction coefficient of the filter cake and the friction torque. That means that the nanoparticles addition to the mud should to prevent the sticking of the drill pipe, and to reduce the downtime costs during drilling associated with the elimination of this phenomenon. 5. Numerical simulation of flow of the developed drilling muds in the borehole with eccentric location and rotation of the drill pipe during the drilling process was carried out. It was determined that the nanoparticles addition significantly effects on the pressure loss in the borehole, the magnitude of the forces and moments of forces acting on the walls of the borehole. It was shown that the nanoparticles addition to the drilling mud can significantly increase the pressure loss in the borehole, caused by increase of the effective viscosity of the drilling mud. It has a negative effect in most cases. On the other hand, it was shown by numerical simulation that the nanoparticles addition to the drilling mud significantly effects on the quality of the borehole flushing. It was demonstrated that as the 2% by weight nanoparticles add to the drilling mud the cutting transport efficiency increases by 18%. Obviously, that the obtained for this period results are not the optimal. Certainly, it is possible to choose such parameters of nanoparticles, which will make these results much higher. Since, in contrast to suspensions with macro and microscopic particles sizes, the rheological parameters of nanosuspensions, the amount of filtration losses, lubricating and sticking capacity depend on the size and material of the nanoparticles and vary significantly even at low concentrations. This offer a broad perspective of the use of nanoparticles to control the characteristics of drilling muds.

 

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Annotation of the results obtained in 2018
The oil and gas industry is one of the most important sectors of the Russian economy. Its sustainable development requires, on the one hand, the exploration of new deposits, and on the other hand, the rational development of existing ones. In particular, it requires the creation of new technologies to increase the oil recovery of already developed reservouirs, the development of previously used and mothballed deposits, and drilling. In addition, such technologies should increase the oil recovery of the developed reservouirs, reduce the environmental load. One of the possible and promising ways to solve these problems is the usage of nanotechnologies in a broad sense. The aim of the carried out by the team in this year researches are the comprehensive and systematic study of the effect of nanoparticles additives of various sizes and composition on the temperature dependence of viscosity and rheological characteristics of drilling fluids, the study of the properties of emulsions and nanoemulsions, the study of interfacial tension and wettability of solutions with nanoparticles and nanoemulsions, as well as numerical simulation of the sludge removal from horizontal wells using drilling solutions with nanoparticles and modelling the penetration of solutions with nanoparticles in the reservoir. In the second year of the project were obtained the following results: 1. The results of a systematic experimental study of the temperature dependence of drilling fluids viscosity modified with nanoparticles of various sizes and compositions were obtained. A sharp change in viscosity and rheological characteristics of water-based drilling fluids with temperature changes is a negative phenomenon, making it difficult to use them during the drilling wells under high temperature conditions. Therefore, the development of drilling fluids with high temperature stability is very topical. It was shown as a result of research that the addition of nanoparticles affects the temperature dependence of the viscosity of clay and clay-polymer suspensions. The addition of nanoparticles makes the drilling mud viscosity less sensitive to temperature changes. So, as the temperature increases from 25 to 80 degrees the effective viscosity of drilling mud with 3 wt.% of silicium dioxide nanoparticles of 10 nm in size increases by about 2.5 times, and at the same time the effective viscosity of drilling mud without nanoparticles increases tenfold. It was found that the effect of the addition of nanoparticles on the viscosity of drilling fluids decreases with increasing the temperature. So, at room temperature the addition of 3 wt.% of nanoparticles increases the viscosity of the clay suspension eightfold, and at 80 degrees such increase is about 3 times. It was shown that the size of nanoparticles also affects the temperature dependence of the drilling fluids viscosity. In general case, a decrease in the nanoparticles sizes leads to an increase in the temperature dependence of the solution viscosity. In general, based on the results of this part of the research, it was found that the viscosity of drilling mud modified by nanoparticles is less affected by temperature, which is very important for their practical application. 2. The results of a systematic study of the developed drilling fluids rheology depending on temperature were obtained. It is shown that as the concentration of nanoparticles increases the effect of temperature on the rheological characteristics of drilling fluids becomes weaker. For example, it was found that the ultimate shear stress of the base solution increases about fifteenfold when the temperature rises from 25 to 80 degrees, while for a solution modified by 3 wt.% nanoparticles of silicium dioxide of 10 nm in size, such increase becomes about 3 times. Thus, it was shown that the addition of nanoparticles makes the rheological properties of clay drilling fluids more stable at different temperatures. It was shown that the temperature dependence of the rheological properties of the studying suspensions also significantly depends on the size of the added nanoparticles, not only on the concentrations. It was found that with decreasing the nanoparticle sizes, their effect on the temperature dependence of the rheological parameters is enhanced. 3. The results of a systematic study of the viscosity and rheological properties of several dozen hydrocarbon-based emulsions and nanoemulsions were obtained. Nowadays, hydrocarbon-based drilling fluids are beginning to widely use in drilling wells. These solutions have a minimal negative impact on the reservoir, have a high suspending and carrying capacity to prevent the accumulation of sludge in the well, have enhanced lubricating properties. Therefore, the further improvement of hydrocarbon-based solutions is very important from a practical point of view. In the course of the project, the effect of the volumetric concentration and type of base oil in the emulsion, the type and concentration of the emulsifier, the temperature and duration of the ultrasonic treatment on the properties of the resulting emulsion was studied. As a result, the necessary reagents were selected and their optimal concentrations were determined, a technology for preparing emulsions with high colloidal and temperature stability was developed. 4. The systematic data of numerical simulation of the sludge particles removal from horizontal wells using drilling fluids modified with nanoparticles were obtained. Currently, drilling of directional inclined wells is widely used in the development of oil and gas fields. Along with the obvious advantages of such wells, in the horizontal areas there are additional difficulties that require further improvement of drilling fluids. As a result of systematic modelling performed in this project, the dependencies of the efficiency of sludge removal and pressure drop in the well on the concentration, size and type of nanoparticles, as well as on the rotation speed of the drill string, on the flow rate of drilling fluid and on the angle of inclination to the horizon of the well were investigated. The study of the nanoparticles additives in the drilling mud effect on the efficiency of sludge transport from a horizontal well showed that the addition of nanoparticles leads to a significant improvement in well washing (2.7 times for a 2% mass concentration of 10 nm silicium dioxide nanoparticles). It was found that as the inclination angle of the well from the vertical increases the positive effect of the nanoparticles addition on the efficiency of sludge removal increases too. In addition, it was shown that the addition of nanoparticles makes the process of sludge transport less sensitive to the inclination angle of the well. Thus, it was shown that the addition of nanoparticles in the drilling fluid will be most effective precisely for horizontal wells. 5. The results of a computational study of the nanofluids penetration into a porous medium were obtained using the task of oil displacing as the example. Analysis of the simulation results showed that the adding of nanoparticles to the displacing fluid significantly affects the process of displacing oil from porous rock. In contrast to the oil displacement by water, which moves along the oil-saturated rock in the form of individual streams, the nanofluid displaces oil by a practically uniform front. As a result, the oil recovery rate significantly increases. It is shown that 1 wt.% concentration of 5 nm silicium dioxide nanoparticles makes it possible to increase oil recovery coefficient by about 2.15 times compared to water. Analysis of the obtained data allowed to establish that the main reason for the increase in oil recovery coefficient in the process of oil displacement by nanofluid is the improvement of rock wettability. 6. The results of experimental studies of interfacial tension and surface wettability in systems: nanoscale suspension / oil / rock; nanoemulsion / stratum water / rock; nanoemulsion / distilled water / rock; oil / water / rock; oil / stratum water / rock were obtained. These data are of paramount importance in the use of nanoemulsions and nanosuspensions to increase the oil recovery rate in the case of water flooding. It was shown that the presence of nanoparticles significantly affects the wettability characteristics of water-oil systems. As the concentration of nanoparticles increases the interfacial tension at the oil / nanosuspension interface decreases (1.7 times at 1 wt.% SiO2 nanoparticles of 31 nm in size), and the contact angle of an oil drop on the rock in the nanosuspension increases very significant (from 71 to 153 degrees). In addition, it was shown that such effect depends on the size of the nanoparticles. As the sizes of nanoparticles decrease the wettability contact angle at the oil / nanosuspension / rock interface increases, and the oil / nanosuspension interfacial tension coefficient decreases. The effect of nanoparticle additives on the wettability of a rock surface with oil in nanosuspension depends substantially on the rock material. The literature review showed that a systematic study of the influence of nanoparticle size on the wettability contact angle and the interfacial tension of the oil / nanosuspension / rock system was performed for the first time. It was found as a result of micro- and nanoemulsions studies that the value of the wettability contact angle decreases with the increasing of oil content in the emulsion. Studies of interfacial tension between the nanoemulsion and water or stratum water showed that the interfacial tension coefficient increases with an increase in the oil content in the emulsion by about 2.3 times. Anomalously low values of the interfacial tension coefficient (3 mN/m) were obtained at low oil content in the emulsion. Thus, it was found that the use of nanosuspensions and nanoemulsions can radically change the wettability of rock by the oil, which can significantly increase the oil recovery factor. It is obvious that the results obtained during this time are far from optimal. Surely, it can be choose such parameters of nanoparticles, at which these results will be even more interesting for practical application. Since, in contrast to suspensions with particle of macro- and microscopic sizes, the properties of nanosuspensions depend on the sizes and material of the nanoparticles and change significantly at even low their concentrations. It opens up a broad perspective for the use of nanoparticles to control the characteristics of drilling fluids and enhance oil recovery during water flooding.

 

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