Multicomponent Hydrocarbon Systems Research Articles

HEAD OF THE COMPLEX LABORATORY OF THE SE «UKRNAUKAGEOCENTR»

Since 2011, the Integrated Analytical Laboratory of the Subsidiary Enterprise of PrJSC «NJSC «Nadra Ukrayny» «Ukrainian geological center of industry research» SE «Ukrnaukageocenter» has been headed by Sіra Nataliіa Vasylivna. Under the leadership and with the participation of Nataliіa Vasylivna, the Integrated Analytical Laboratory of SE «Ukrnaukageotsentr» conducts determination of physical and chemical properties of reservoir oils as complex multicomponent hydrocarbon systems, conducts experimental studies of samples. According to the analysis of the results of experimental studies of the water-gas system, in simulated reservoir conditions, it is proved that nitrogen, based on its physical and chemical characteristics, can be used as a geochemical indicator of the process of anticipatory watering of deposits of gas condensate deposits. The result of its growth was the defense of a candidate's thesis in 2015 on the topic «Development and application of complex geological and geochemical methods for forecasting the watering of gas condensate deposits».

Исследование пластового флюида при разработке месторождений на шельфе Kарского моря

Introduction. With the expansion of offshore drilling and the distance of fields from the coastline, the number of production wells located in difficult underwater geological conditions is increasing, which complicates research. For example, the Yurkharovskoye field is located in a strip along the Tazovsky Peninsula under the waters of the Kara Sea. At the same time, the data obtained from the results of research are necessary when calculating reserves and designing the development of hydrocarbon deposits. Materials and research methods. Modeling of the operating conditions of the field under various thermodynamic conditions was carried out in order to determine the effect of water vapor and oil fractions on condensate losses during the development of the deposit [6–9]. The experiments were carried out to determine the amount of condensate in the reservoir gas, the physicochemical properties of hydrocarbons, and the effect of heavy oil fractions on condensate recovery [5, 10]. Prediction of condensate losses in the reservoir depending on the influence of negative factors must be taken into account when calculating hydrocarbon reserves and drawing up a field development project [11, 13]. Research results and their discussion. In the studied part of the section of the Yurkharovskoye field, located on the shelf of the Taz Bay, gas deposits were identified in the Aptian-Albian-Cenomanian complex and gas condensate deposits with oil rims in the Neocomian complex. The selection of development objects was based on a set of geological and geophysical data, the main of which are the presence of reservoirs and seals in the section and a single hypsometric position of the GWC or WOC in the case of an oil and gas condensate deposit. Correlation of well sections and identification of productive formations was based on the choice of benchmarks, the similarity of well logs, taking into account the nature of reservoir saturation and well test results. As a result of experimental PVT studies, the influence of water vapor and oil fractions as an integral part of the hydrocarbon system on the reservoir losses in the deposit was determined. The analysis of the performed studies confirmed that multicomponent hydrocarbon systems consist of a mixture of gas, condensate and water vapor, as well as oil fractions, which significantly changes the properties of the system and the dynamics of its phase processes during the development of the Yurkharovskoye field. Conclusions. The conducted PVT-experiments in order to identify the effect of water vapor and oil components that are part of natural gas showed that the predicted current and final condensate recovery factors are overestimated. An analysis of the research results revealed a different effect of water vapor on reservoir losses of hydrocarbons in the deposit due to an increase in partial pressure. In the presence of formation water in the gas condensate system, the CFC value decreased to 4-5%. Thus, the reason for the increase in reservoir losses of condensate in the deposit during the development of oil and gas condensate fields on the shelf of the Kara Sea was determined.

A multi-layer perceptron neural network model for predicting the hydrate equilibrium conditions in multi-component hydrocarbon systems

A multi-layer perceptron neural network model for predicting the hydrate equilibrium conditions in multi-component hydrocarbon systems

Thermodynamic Analysis of Relaxation Model for Non-Equilibrium Phase Behavior of Hydrocarbon Mixtures

Mathematical models of phase behavior are widely used to describe multiphase oil and gas-condensate systems during hydrocarbon recovery from natural petroleum reservoirs. Previously a non-equilibrium phase behavior model was proposed as an extension over generally adopted equilibrium models. It is based on relaxation of component chemical potentials difference between phases and provides accurate calculations in some typical situations when non-instantaneous changing of phase fractions and compositions in response to variations of pressure or total composition is to be considered. In this paper we present a thermodynamic analysis of the relaxation model. General equations of non-equilibrium thermodynamics for multiphase flows in porous media are considered, and reduced entropy balance equation for the relaxation process is obtained. Isotropic relaxation process is simulated for a real multicomponent hydrocarbon system with different values of characteristic relaxation time using the non-equilibrium model implemented in the PVT Designer module of the RFD tNavigator simulation software. The results are processed with a special algorithm implemented in Matlab to calculate graphs of the total entropy time derivative and its constituents in the entropy balance equation. It is shown that the constituents have different signs, and the greatest influence on the entropy is associated with the interphase flow of the major component of the mixture and the change of the total system volume in the isotropic process. The characteristic relaxation time affects the rate at which the entropy is approaching its maximum value.

Adsorption, selectivity, and phase behavior in organic nanopores for shale gas and oil development

In a shale gas and oil reservoir, hydrocarbon fluids are stored in organic nanopores with sizes on the order of ∼1–100 nm. The adsorption, selectivity, and phase behavior of hydrocarbons in the nanopores are crucial for estimating the gas-in-place and predicting the productivity. In this study, to understand the characteristics of the phase behavior of multicomponent hydrocarbon systems in shale reservoirs, the phase behavior of a CH4/n-C4H10 binary mixture in graphite nanopores was investigated by Grand Canonical Monte Carlo (GCMC) molecular simulation. The method for determining the dew-point pressure and bubble-point pressure in the nanopores was explored. The condensation phenomenon was observed owing to the difference in the adsorption selectivities of the hydrocarbon molecules on the nanopore surfaces, and hence the dew-point pressure (and bubble-point pressure) of hydrocarbon mixtures in the nanopores significantly shifted. The GCMC simulations reproduced both the higher and lower bubble-point pressures in nanopores in previous studies. This work highlights the crucial role of the selectivity in the phase behavior of hydrocarbons in nanopores.

Investigations of temperature and dilution effect on rheological properties of waxy crude oil

The purpose of the paper is to study the effect of temperature and hydrocarbon solvent addition on thixotropy of waxy crude oil. Oil is a complex multicomponent hydrocarbon system. There are many interactions between wax and asphaltene, wax and aromatics, asphaltene and resins in original oil. For example, the dispersion of asphaltenes is known to be influenced by resins. The resins are adsorbed onto the surface of the asphaltenes, whereby the asphaltenes are not aggregated. Wax is adsorbed by fine asphaltene particles and wax appearance temperature (WAT) observed at low temperature (formed wax crystals too small to be detected by measuring system). The authors of the paper have studied the separate effect of two solvents (kerosene and diesel fuel), wax concentration and impurities (kaolinite) on WAT to understand how all these factors affect WAT in wax-bearing solutions individually. Wax-bearing solutions in wax concentration range from 10 to 60% by weight were investigated by the visual and rheological methods under atmospheric pressure. It is shown that the diesel-based solutions have higher WAT than the kerosene-based solutions. Studies have shown that the increase in wax concentration in solution leads to an increase in WAT. The paper describes that the addition of impurities (kaolinite) to the solutions resulted in an increase in WAT. Besides, it is shown that WAT obtained by rheological method is higher on average of 1 °C than WAT obtained by visual method. The authors suggested that under constant other conditions (pressure, resin and asphaltenes content, etc.) an increase in wax content in oil and the content of impurities will lead to an increase in WAT. The scientific basis for this conclusion is that, in the future we can, adding or removing from solution hydrocarbon components, with certain assumptions, simulate the properties of oil. In particular, this will allow us to study separate interactions between the wax and asphaltene, wax and aromatics, and wax and naphtha compounds, and abstract away from other factors. The waxy crude oil production in the Samara region is complicated by impurities entrainment and non-Newtonian properties of oil. The investigations of waxy crude oil were provided with light scattering method (in near infrared region), microscopy under high pressure with the grain size analysis (visual) and a rheological method. We obtained the unique «viscosity superanomaly» discovered by Vinogradov and Malkin (Rheol Acta 5(3):188–193, 1966) at low temperatures and shear stress by rheological method under atmospheric pressure. The area of the hysteresis loop on the flow curve increases as the temperature decreases, which is caused by the formation of the lattice by wax. We have also shown that the use of solvent and the increase in temperature allow to reduce «viscosity superanomaly». Simultaneous use of light scattering and microscopy under high-pressure methods allows increasing in accuracy of measuring. For waxy crude oil, there will also be a difference between rheological and visual methods of WAT measuring, as these methods have different sensitivity limits. Besides, the study showed that addition of N2 and CO2 to oil leads to decrease in WAT. However, it is necessary to provide a number of additional studies before gas injection projects in the field. For example, it is shown that CO2 injection leads to asphaltenes precipitation in oil by many scientists. Novelty of the paper consists in investigation of rheological properties of waxy crude oil of the Samara and the effect of nonhydrocarbon gases on WAT. In this study, unique flow curves of oil of the Samara region were obtained.

Study of nanoconfined mixtures of decane and water: Structure and dynamic

In the last years, the phase behaviour of multi-component hydrocarbon systems in shale reservoirs has received significant attention. The main complexities in modelling the phase behaviour is the confinement. It is presented in this work, the results obtained by molecular dynamics simulation in the NPT ensemble of n-decane/water liquid mixture confined in an amorphous hydrophobic nanometric tube. Nanotube walls are made up of a Lennard-Jones binary mixture similar to a Kob-Andersen system. As it happens in a macroscopic flow of biphasic fluid, a transition from drop to a thread is observed in this confined system when increasing water molar fraction. Different values of the water tetrahedral bond distribution, water density profiles, and the mean square-displacement of water were found for a drop to a thread transition. The calculated quantities, substantially differ from those corresponding to the bulk system.

Molecular simulation of the constant composition expansion experiment in shale multi-scale systems

The phase behavior of hydrocarbons in shale reservoirs has garnered increasing attention in the petroleum industry. Significant differences in the phase behavior of petroleum fluids between conventional reservoirs and shale reservoirs have been observed. Because of the existence of nano-scale porous media in shale reservoirs, there are substantial surface fluid interactions that can lead to a heterogeneous distribution of molecules and an alteration of the fluid phase behavior. In this work, for the first time, we use molecular simulations to investigate the confinement effect on the phase behavior of reservoir fluids in a multi-scale (nano-scale + macro-scale) media. The model has a confined region that mimics the nano-scale porous media and a bulk region that represents the macro-scale porous media (macropores and fractures) in shale reservoirs. For the first time, we use the Gibbs ensemble Monte Carlo (GEMC) simulation at imposed pressures to simulate the constant composition expansion (CCE) experiment for multi-component hydrocarbon mixtures in a multi-scale porous media. Our results show that because of the confinement effect, the composition of the bulk and the confined regions differ significantly. In our molecular simulations, the composition of the lighter components in the bulk region increases, while heavier components are mainly trapped in the confined region. These changes in the composition cause a significant shift or disappearance of the saturation pressure in the bulk region of the multi-component multi-scale hydrocarbon systems.

Application of REFPROP software package for examinations automation of phase states of multicomponent hydrocarbon systems

This article is concerned with the automation of the experimental examinations of the phase states of multicomponent hydrocarbon systems. Experimental examinations of the mixtures of natural gas and gas condensate from the gas-condensate field on the PVT-installation have been performed to determine if the composition of the hydrocarbon mixtures influence the regularities of their phase changes. The comparison of the calculations by means of the REFPROP software package with the experimental data of Russian and foreign authors show that this software program can be used for automatization of the estimated calculations of the phase balances in the range of low temperatures as well as for controlling of the critical parameters of hydrocarbon mixtures. The authors demonstrate the possibility of the REFPROP software package application for choice automation of the hydrocarbon mixture composition for transportation in the low-temperature pipelines in the chosen range of temperatures and pressures.

The calculation of the phase equilibrium of the multicomponent hydrocarbon systems

Hydrocarbon mixtures filtration process simulation development has resulted in use of cubic equations of state of the van der Waals type to describe the thermodynamic properties of natural fluids under real thermobaric conditions. Binary hydrocarbon systems allow to simulate the fluids of different types of reservoirs qualitatively, what makes it possible to carry out the experimental study of their filtration features. Exploitation of gas-condensate reservoirs shows the possibility of existence of various two-phase filtration regimes, including self-oscillatory one, which occurs under certain values of mixture composition, temperature and pressure drop. Plotting of the phase diagram of the model mixture is required to determine these values. A software package to calculate the vapor–liquid equilibrium of binary systems using cubic equation of state of the van der Waals type has been created. Phase diagrams of gas-condensate model mixtures have been calculated.

Расчет дискретных функций характеристических кривых фазового поведения многокомпонентных углеводородных систем

Расчет дискретных функций характеристических кривых фазового поведения многокомпонентных углеводородных систем

Dynamic Viscosity and Compensation Effect in Hydrocarbon Media with a High Content of Resins and Paraffins

Linear dependences have been obtained for multicomponent hydrocarbon media (oils and high-boiling fractions), which relate the preexponent and the activation energy of viscous flow in the Arrhenius equation. A distinctive feature of the established kinetic compensation effect is it existing before and after the phase-transition temperature. The obtained results have been confirmed by statistical data and make it possible to predict the dynamic viscosity of multicomponent hydrocarbon systems, such as oil and high-boiling fractions.

Specificity Switching Pathways in Thermal and Mass Evaporation of Multicomponent Hydrocarbon Droplets: A Mesoscopic Observation

For well over one century, the Hertz–Knudsen equation has established the relationship between thermal – mass transfer coefficients through a liquid – vapour interface and evaporation rate. These coefficients, however, have been often separately estimated for one-component equilibrium systems and their simultaneous influences on evaporation rate of fuel droplets in multicomponent systems have yet to be investigated at the atomic level. Here we first apply atomistic simulation techniques and quantum/statistical mechanics methods to understand how thermal and mass evaporation effects are controlled kinetically/thermodynamically. We then present a new development of a hybrid method of quantum transition state theory/improved kinetic gas theory, for multicomponent hydrocarbon systems to investigate how concerted-distinct conformational changes of hydrocarbons at the interface affect the evaporation rate. The results of this work provide an important physical concept in fundamental understanding of atomistic pathways in topological interface transitions of chain molecules, resolving an open problem in kinetics of fuel droplets evaporation.

High-Temperature Compensation Effect of Dynamic Viscosity in Multicomponent Hydrocarbon Media

Linear dependences connecting the preexponent to the activation energy of viscous flow in the Frenkel–Eyring equation have been obtained for multicomponent hydrocarbon media (high-boiling distillate fractions). For these media, the kinetic compensation effect has been established whose distinctive feature is its action in the temperature range including the temperature of thermal destruction (400–450°C) of the indicated media. The obtained results have been confirmed by statistical-processing data and make it possible to predict the dynamic viscosity of multicomponent hydrocarbon systems, such as tars and other high-boiling oil distillates.

Impact of surfactants in micro concentrations on certain properties of organic liquids as a basis for improving some oil-and-gas industry processes and properties of gasoline

Surface physicochemical phenomena have a crucial role in phase interaction and in various processes in real heterogeneous systems with an advanced interfacial surface. Research into application opportunities for highly-effective surfactants in the processes of the oil-and-gas industry and the usage of petroleum products is essential. The purpose of the work is to increase the understanding of the impact of introducing surfactants in micro-concentrations on certain physical properties of multicomponent hydrocarbon systems, individual hydrocarbons and their derivatives. Patterns of the surfactants’ micro concentrations effect on the surface tension, vapor pressure, boiling rate under given conditions and the rate of the phase transition “vapor-liquid” were substantiated. Recommendations on the use of surfactants in the processes of the oil-and-gas industry (rectification by various technologies, glycol dehydration of gases, adsorptive fractionation of the associated petroleum gas, storage of petroleum and light petroleum products in tanks) and the improvement of the properties of gasoline were proposed.

Phase behavior of multi-component hydrocarbon systems in nano-pores using gauge-GCMC molecular simulation

In recent years, the phase behavior of hydrocarbons in shale reservoirs has received significant attention. One of the main complexities in modeling the phase behavior in shale reservoirs is the confinement effect. Surface–fluid interactions in nanoscale shale pores can lead to a heterogeneous distribution of molecules and can significantly alter the phase behavior compared to that in bulk conditions. Molecular simulation has shown promising results in modeling phase behavior under confinement. In this study, we present a novel molecular simulation method for studying the confinement effect on the phase behavior of multicomponent systems. We validate our method by comparing the phase diagrams of pure and binary hydrocarbon systems with experimental data (where available) and the simulation results from other techniques. We also apply the proposed method in modeling the phase behavior of a ternary system (C1/C3C5) under a 4 nm slit pore confinement. Our results show that critical density increases under confinement in binary and ternary systems, and the confinement effect produces in a significant shift in the composition of the critical point. Heavier components have a higher concentration in the adsorbed layers than that of lighter components, which results in significant phase density differences under confinement.

Feasibility of combination of CO2 geological storage with geothermal-type water-soluble gas recovery in Yinggehai Basin, China

Carbon dioxide capture, utilization and storage (CCUS) is an important technology to combat global climate change. Carbon dioxide (CO2), a greenhouse gas, can also be used to extract lighter components from subsurface fluids in a multicomponent hydrocarbon system. In many oil and gas bearing basins, there are high temperature and high pressure aquifers saturated with methane. These aquifers are usually known as geothermal-type water-soluble gas reservoirs. The geothermal-type water-soluble gas reservoirs have great potential for coupled development to harvest thermal energy and natural gases. Additionally, the aquifers can serve as favorable sites for CO2 geological sequestration.This paper proposes a new feasible technology that combines CO2 geological sequestration with geothermal-type water-soluble gas recovery (CO2-GWSGR). This proposed technology injects CO2 into the pressurized aquifer for greenhouse gas reduction and natural gas and thermal energy development. In the Yinggehai Basin, there are rich water-soluble gas resources and some natural gas wells that produce CO2. Based on the reservoir characterization of the Yinggehai Basin, a 3-D conceptual model was designed and simulated using the TOUGH2/EOS7C program. Simulation results show that CO2 injection can effectively enhance recovery of water-soluble gas. Sensitivity studies indicate that CO2 storage and energy production increase with the increases in well spacing and reservoir thickness. Numerical simulation was used to model the impact of factors such as reservoir heterogeneity and injection fluid on thermal energy recovery and CO2 storage. Simulation results show that the economic revenue per ton of CO2 storage under injecting fluid with the dissolved CO2 is approximately 18 times greater than that of injecting pure CO2. This revenue will offset the capture and storage costs of CO2 to a large extent. Considering the economics and the escape risk of carbon dioxide in aquifers, injecting fluid with the dissolved CO2 is the best injection method. The results of CO2-GWSGR technology provide new perspectives and valid technical references for geothermal-type water-soluble gas production and carbon dioxide storage.

Evaluation of physico-chemical properties of hydrocarbon systems based on spectrum-property and color-property correlations

Express methods are proposed for determination of physico-chemical properties of multi-component hydrocarbon systems based on principles correlating physicochemical and optical properties of substances, i.e., based on spectrum-property and color-property correlations. Statistical processing of data acquired indicates that the proposed express methods are in no way inferior to conventional investigatory methods in accuracy.

Determination of Physicochemical Properties of Multicomponent Hydrocarbon Systems Based on Integral Characteristics of Electronic Absorption Spectra

A spectroscopic method based on the law correlating the physicochemical properties of substances and their integral electronic radiation absorption characteristics in the visible and/or UV range has been developed for determining the physicochemical properties of various multicomponent hydrocarbon systems. This method can be used for rapid monitoring of hydrocarbon feedstock quality and performance characteristics of oil refining and petrochemical plants.

Nonlinear compensation effect of dynamic viscosity of multicomponent hydrocarbon systems

A nonlinear compensation effect determining the dependence of the energy of a flow of a Newtonian liquid on the preexponent of its viscosity was detected. Empirical dependences relating the softening temperature of a Newtonian high-molecular multicomponent hydrocarbon system with the activation energy of its viscous flow have been obtained. The results obtained are supported by the statistical data and allow one to predict the dynamic viscosity of oil and coal fractions and materials based on them.