Criterion of phase stability of asphaltenes in crude oils

Associate formation processes in crude oils are investigated by viscometry and dielectric spectroscopy. It is shown that fluidity decline in the 36-40 C range is typical for crude oils with a high resin and asphaltene content ratio. The critical polar resin concentration in stable asphaltene nanoaggregates is determined. © 2013 Springer Science+Business Media New York

The influence of carbonate rock on the processes of oil transformation

© 2018 Taylor & Francis Group, LLC. The study of the processes of crude oil transformation in carbonate rock was carried out on the “oil–carbonate rock” model systems. For the study, oils of different chemical composition recovered from both terrigenous and carbonate reservoirs, and rock from carbonate reservoir were selected. It was shown that not all oils were subjected the catalytic action of carbonate rock. In oils that have experienced the catalytic action of carbonate rock the content of aromatic hydrocarbons decreased significantly and the content of non-polar resins increased. In carbonate rock, in addition to calcite and aragonite the montmorillonite was detected and it was supposed that the catalytic effect of the carbonate rock was due to this clay mineral. It was found that the oil transformation in the carbonate rock did not require much time and high temperature, and also that the oil recovered from the carbonate reservoir was resistant to the catalytic action of the carbonate rock

Characteristics of compatability of high-viscosity oils

© 2015 Springer Science+Business Media New York. The physicochemical properties (density, viscosity, precipitation resistance of sphaltenes) of blends of high-viscosity oils from Permian deposits (Ashal'cha field) with arboniferous oils from the Yamashi field (Tatarstan) are studied. It is demonstrated that when high-viscosity oils are blended, various structure-formation processes that are accompanied by non-additive changes of density, viscosity, and stability may occur. The concentration range of Carboniferous oil in the blend at which the maximum sedimentation resistance and minimum density and viscosity of the blend are attained is determined. It is shown that the change in asphaltene content in the blends is non-additive

Distribution of Paraffin Hydrocarbons and Asphaltenes in Acidic Water-Oil Emulsion

© 2018, Pleiades Publishing, Ltd. Abstract: Asphaltenes and solid paraffins isolated from various layers of acidic water-oil emulsions obtained by mixing an oilfield emulsion with 15% solutions of hydrochloric and sulfamic acids with or without addition of Fe(III) have been studied by elemental analysis, IR and EPR spectroscopy, gas–liquid chromatography, and calorimetry. In acidic water-oil emulsions, the high-molecular-weight petroleum components have not been found to concentrate at the oil/water interface; however, a change in their composition has been revealed, which is more pronounced in the presence of Fe(III). The formation of diamagnetic complexes of the paramagnetic centers of asphaltenes with Fe(III) has been detected

Modelling of the thermal treatment process for oil deposit in the carbonate formation

© 2018, Neftyanoe Khozyaistvo. All rights reserved. The experience of oilfield development shows that at present when oilfields with heavy oils are developed the thermal methods, in particular thermal steam stimulation, have no alternative and have a priority among other methods. The thermal methods are most relevant for development of complex carbonate reservoirs, in which more than 60% of the world's oil reserves are concentrated. However, the recovery factor of the deposit is mostly very low. This is due to the textures complexity of carbonate reservoirs, the high heterogeneity of their composition and physical-chemical properties. Problems of carbonate reservoirs’ development are dramatized by high oil density and viscosity of oil. Model experiments with variation of temperature, pressure and composition of the injected heat carrier will allow creating scientific bases of thermal technologies for development of carbonate reservoirs. The paper presents the results of a laboratory study of thermal stimulation of carbonate rock of the oil reservoir. The investigation was carried out on a specially designed flow-type setup equipped by original core holder. The core samples were selected from the Middle Carboniferous deposits of the Republic of Tatarstan. The influence of the composition of steam-gas eluent, temperature, and pressure on the permeability of carbonate rock, the composition both of gaseous thermolysis products and recoverable oil, and the efficiency of oil recovery from the carbonate rock were discussed. A relatively low-temperature (400 °C) decomposition of carbonates initiated by water vapor was established. It was shown that the thermal steam treatment at temperatures up to 500 °C was not accompanied by the destruction of oil components at a pressure of 4,0 MPa in the condensation zone. The most economical and ecological version of the thermal steam stimulation method for the carbonate oil reservoir was proposed

Change in the structural-group composition of bitumen asphaltenes upon thermal bitumen recovery

© 2017, Pleiades Publishing, Ltd.Comparative analysis of thermal analysis and EPR spectroscopy data on asphaltenes from Ashal’chinskoe and Mordovo-Karmal’skoe bitumens recovered by steam drive and in situ combustion has been performed. It has been found that the steam drive does not alter the structural-group composition of asphaltenes whereas the in situ combustion lead to conversion of asphaltenes into coke-like particles deposited onto the rock surface in the reservoir. It has been shown that the asphaltenes with a high proportion of condensed aromatic entities are carriers of genetic information on the petroleum system

Photoswitching of a thermally unswitchable molecular magnet Cu(hfac) 2Li-Pr evidenced by steady-state and time-resolved electron paramagnetic resonance

Most photoswitchable molecular magnets exhibit thermally induced switching, as is typical of spin crossover (SCO), valence tautomerism and SCO-like phenomena. We report a rare case of a copper-nitroxide based molecular magnet Cu(hfac)2Li-Pr that does not exhibit quantitative SCO-like behavior in the temperature range of its chemical stability (2-350 K); however, it can be switched to a metastable thermally inaccessible spin state via visible/near-IR light at cryogenic temperatures. By means of photogeneration, unique information on this otherwise unobservable spin state has been obtained using steady-state Q-band (34 GHz) and time-resolved W-band (94 GHz) electron paramagnetic resonance (EPR) spectroscopy. In particular, we have found that the electronic structure and relaxation properties of the photoinduced state in Cu(hfac)2Li-Pr are very similar to those in its sister compound Cu(hfac)2Ln-Pr that is thermally switchable and has been exhaustively characterized by many analytical methods, previously. The first observation of photoswitchable behavior in a thermally unswitchable copper-nitroxide based molecular magnet Cu(hfac)2Li-Pr paves the way for photoswitching applications of this and similar compounds in the remarkably broad temperature range of 2-350 K. © 2014 American Chemical Society

Heterospin complex showing spin transition at room temperature

© 2015 Elsevier Ltd. All rights reserved. New nitronyl nitroxides LMe and LMe-CP containing a 4-methylpyridin-3-yl substituent were synthesized. It was found that the interaction of Cu(hfac)2 with LMe and LMe-CP gave binuclear [Cu(hfac)2LMe]2 and [Cu(hfac)2LMe-CP]2·Solv (Solv = n-C6H14, n-C10H22, n-C16H34) and chain polymer {[[Cu(hfac)2]2LMe2][Cu(hfac)2]}∞ heterospin complexes. An important structural peculiarity of LMe and LMe-CP is a large dihedral angle between the planes of the O•-N-CN → O paramagnetic fragment and the pyridine ring: 55.2 and 56.1°, respectively. The presence of a methyl group in the pyridine ring of the nitroxide molecule in {[[Cu(hfac)2]2LMe2][Cu(hfac)2]}∞ proved favorable for spin transition at nearly room temperature

Criterion of phase stability of asphaltenes in crude oils

Associate formation processes in crude oils are investigated by viscometry and dielectric spectroscopy. It is shown that fluidity decline in the 36-40 C range is typical for crude oils with a high resin and asphaltene content ratio. The critical polar resin concentration in stable asphaltene nanoaggregates is determined. © 2013 Springer Science+Business Media New York

Size effect for asphaltene particles in the resin by NMR

© Kazan Federal University (KFU). The resin-asphaltene model systems with different sizes of asphaltenes are studied by nuclear magnetic resonance (NMR) using the solid-echo sequence. For systems with particle sizes of asphaltenes greater than 50 µm, the form of relaxation attenuation consists of two components, one of which is characterized by a typical asphaltene relaxation time of about 20 µs. In this case, the Gaussian form describes the relaxation attenuation of this component, which is typical for the NMR signal in disordered solids. At the same time, it is found that the share of the solid component in the NMR signal decreases with decreasing particle size of asphaltenes. The signal drops to zero when the size of asphaltenes particles reaches 10 microns. Based on the estimates of the rotational motion correlation time for an asphaltene particle in a dispersion medium (resin) with a known viscosity value, the influence of two factors is discussed: the difference in the values of macro-and microviscosity of the resin, as well as the possibility of partial dissolution of asphaltenes particles in the resin. The results of repeated measurements for a long time indicate the existence of a reverse process in the system, leading to the aggregation of asphaltene particles