Gas Viscosity Research Articles

Effect of carrier gas type on feeding characteristics of powder supply system

The new powder engine is an efficient power system with powder fuel as propellant. Its excellent performance is inseparable from stable and efficient powder feeding assisted by carrier gas. In this paper, we investigate the effect of carrier gas type (air, N2, CO2 and He, gas viscosity: CO2<N2<air<He) on the powder feeding characteristics of the powder supply system. The experimental results show that the change in carrier gas types has an insignificant effect on the powder flow pattern, but greatly affects the powder mass flow rate, pressure distribution and gas velocity in the silo, which is owing to the difference in the gas viscosity. Moreover, the analysis of powder column stress state reveals that the powder axial stress is related to the gas phase pressure gradient in the powder column. Specifically, under the same differential pressure, the smaller the gas viscosity, the higher the permeability, the greater the gas phase pressure gradient, the greater the powder axial stress pressure transferred to the outlet, thus obtaining a higher mass flow rate. However, energy analysis indicates that the smaller the gas viscosity, the higher the energy consumption required to transport the same mass powder. We hope our findings can provide ideas and references for efficient powder feeding.

An improved transport model in shale nanopores based on advection diffusion method

As an unconventional oil and gas resource, shale gas plays a very important role in global energy supply. A breakthrough in efficient exploitation of shale gas is how to accurately describe the percolation mechanism of shale gas in nano-pores. In this article, a new shale gas apparent permeability model is established on the basis of advection diffusion model and considering adsorption stress effect and gas viscosity correction. On this basis, the influence factors of apparent permeability, the comparative difference between stress effect or not and viscosity correction or not, and the contribution of gas flow mechanism are studied. The results show that: the apparent permeability decreases with the increase of pressure, increases with the increase of pore radius, and increases with the increase of temperature; when the pore radius increases, the difference caused by stress correction becomes obvious; when the pressure decreases, the difference caused by viscosity correction becomes obvious. The results can provide some new ideas and methods for the study of gas flow mechanism in microscopic nano-pores.

A Study on the Production Performance of a Horizontal Shale Gas Well Using a Fully Coupled Flow and Geomechanics Modeling

Conventional petroleum reservoir simulators use constant rock compressibility to denote rock deformation. However, due to the stress-sensitive nature of the shale formations, using constant rock compressibility in reservoir simulators does not accurately capture the pressure diffusion in the reservoir, leading to a higher error margin in flow rate estimation. Fluid flow coupling with geomechanics is used to account for such a phenomenon numerically. Such an approach is important for shale numerical studies and any energy underground storage modeling (i.e., CO2 storage). Usually, when fluid flow coupling with geomechanics is studied for shale formations, the fluid, and the stimulated reservoir petrophysical properties are overlooked. This paper aims to present a study on the effect of the fluid and reservoir petrophysical properties on the performance of a gas-producing well. In addition, the results from the cases when geomechanics is coupled and decoupled with fluid flow in reservoir simulations are compared. The governing equations were discretized using the Finite Element Method. First, the model was validated against Terzaghi's consolidation theory analytical solution. After that, a history matching for the production flow rate was performed using field production data from Barnett Shale. Then a sensitivity analysis was carried out for the gas viscosity, Stimulated Reservoir Volume (SRV) porosity, and fracture conductivity. Next, the sensitivity analysis was conducted for the coupled and decoupled cases. Finally, the sensitivity analysis results were compared between the coupled and decoupled cases. The results show that lower gas viscosity, higher SRV porosity, and higher fracture conductivity improved horizontal well production performance. In addition, when the geomechanical effects were decoupled, the reservoir simulator overestimated the production flow rate and cumulative production.

Strain evolution in coal seam exposed to injected gas with different species for enhanced CBM extraction: a numerical observation

The viscosity and density of different gases (CO2 and N2) vary with the gas species, composition and temperature, which may raise variant results of gas injection enhanced coalbed methane (ECBM) extraction. The fluid–structure interaction within the coal seam was established to study the evolution of coal strain in the process of ECBM extraction by injecting CO2 or N2. After verifying the equations governing the interaction via experimental tests, the ECBM extraction by injecting different gases was simulated. The characteristics of coal strain induced by gas sorption was comprehensively analyzed. Results show that N2 has strong fluidity in coal fractures, leading to wider influencing range of injected N2 than that of injected CO2. Due to the greater affinity of CO2 to coal, the effect of gas displacement and competitive sorption is more obvious, manifesting in more likely to migrate towards the coal matrix. Compared with regular extraction, the CH4 content at 180d in CO2-ECBM and N2-ECBM extraction has decreased by 24.3% and 13.8%, respectively. The effect of gas extraction is CO2-ECBM > N2-ECBM > regular extraction. The coal strain induced by gas sorption mainly depends on the proportion of adsorbed gas in the coal matrix. The permeability evolution is opposite to the coal strain induced by gas sorption. For CO2-ECBM, the proportion of CH4 decreases gradually caused by the competitive sorption with CO2 in matrix, and the coal strain increases. The influencing factors on the coal strain are injection pressure, initial permeability, water saturation and extraction pressure in order. While for N2-ECBM, the influencing factors on the coal strain are initial permeability, injection pressure, water saturation and extraction pressure in order.

Effects of temperature on seepage capacity for a multi-type ultra-deep carbonate gas reservoir

Ultra-deep carbonate gas reservoirs are buried at great depths and have high temperatures, and the impact of high temperature on the seepage capacity of multi-type reservoirs is still unclear. The study selected cores from the fourth member of Dengying Formation in the Gaoshiti-Moxi area to measure the gas single-phase permeability of rock samples during the heating and cooling process, as well as the gas-water interfacial tension and gas-water two-phase relative permeability at different temperatures. This allowed researchers to obtain the effect of temperature on the seepage capacity of multi-type ultra-deep carbonate gas reservoir. The research results show that within the range of 20–120 °C, with the change of temperature, the gas single-phase seepage capacity of different types of reservoir rock samples changes as a power function. The decrease in gas-phase permeability during the heating process is jointly affected by the increase in gas viscosity, the expansion of dolomite crystals, and the migration of rock particles after embrittlement. After one heating and cooling process, fractured-cavity type rock samples had the highest irreversible degree of permeability at 82.52%, due to the development of micro-fractures, followed by 27.63% for pore type due to the development of small pores and throats, and the lowest was 9.46% for pore-cavity type. Fractured-cavity rock samples are temperature-sensitive, while pore-type and pore-cavity-type rock samples are temperature-resistant. The upper-temperature limit of the target multi-type gas reservoir is concentrated around 46–50 °C. The temperature increase mainly improves the gas-displacing water efficiency and gas-water two-phase seepage capacity by reducing the water-gas viscosity ratio, which is about 1/3 of the normal temperature at the formation temperature. The gas-water phase permeability curves of multi-type reservoirs under high-temperature conditions can better represent the two-phase seepage characteristics of actual formations. The effect of temperature on the seepage capacity of multi-type ultra-deep carbonate gas reservoirs can provide a theoretical basis for the efficient development of such gas reservoirs.

Prediction of the viscosity of natural gas at high temperature and high pressure using free-volume theory and entropy scaling

Eighteen models based on two equations of state (EoS), three viscosity models, and four mixing rules were constructed to predict the viscosities of natural gases at high temperature and high pressure (HTHP) conditions. For pure substances, the parameters of free volume (FV) and entropy scaling (ES) models were found to scale with molecular weight, which indicates that the ordered behavior of parameters of Peng-Robinson (PR) and Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) propagates to the behavior of parameters of viscosity model. Predicting the viscosities of natural gases showed that the FV and ES models respectively combined with MIX4 and MIX2 mixing rules produced the best accuracy. Moreover, the FV models were more accurate for predicting the viscosities of natural gases than ES models at HTHP conditions, while the ES models were superior to PRFT models. The average absolute relative deviations of the best accurate three models, i.e., PC-SAFT-FV-MIX4, tPR-FV-MIX4, and PC-SAFT-ES-MIX2, were 5.66%, 6.27%, and 6.50%, respectively, which was available for industrial production. Compared with the existing industrial models (corresponding states theory and LBC), the proposed three models were more accurate for modeling the viscosity of natural gas, including gas condensate.

Effects of gas viscosity and liquid-to-gas density ratio on liquid jet atomization in crossflow

Atomization of liquid jets in gaseous crossflows has many natural and industrial applications, for example, in fuel atomization in gas turbine engines, rocket engines, film cooling, and, recently, suspension and solution precursor plasma spraying processes for the development of advanced coatings. Viscosity and density of the gaseous medium may significantly vary in applications such as plasma spraying, which can affect the instability waves on the liquid jet column, resulting in a major change in the mechanism of primary and secondary breakups. In this study, a numerical model is used to investigate the impact of gas viscosity on breakup mechanisms for a wide range of density ratios and Weber numbers. Due to many challenges, only a few comprehensive atomization measurements have been performed on this subject. However, novel computational models could provide the atomization process with a thorough picture in the last two decades. The incompressible variable-density Navier–Stokes equations are solved by using finite volume schemes, and a geometric volume-of-fluid technique is used to track the gas–liquid interface. In our parametric study, three sets of density ratios and Weber numbers are chosen. In each set, four cases with different orders of magnitude of gaseous Reynolds number are simulated. Different characteristics of jet atomization are analyzed, such as the jet trajectory, breakup location, and surface instabilities generated along the jet column. Ultimately, the effects of gaseous Reynolds number, density ratio, and Weber number on jet deformation and breakup mechanisms are discussed.

Viscous dissipation in a gas of one-dimensional fermions with generic dispersion

A well-known feature of the classical monoatomic gas is that its bulk viscosity is strongly suppressed because the single-particle dispersion is quadratic. On the other hand, in condensed matter systems the effective single-particle dispersion is altered by lattice effects and interactions. In this work, we study the bulk viscosity of one-dimensional Fermi gases with generic energy-momentum dispersion relations. As an application, viscous dissipation arising from lattice effects is analyzed for the tight-binding model. In addition, we investigate how weak interactions affect the bulk viscosity. Finally, we discuss viscous dissipation in the regime in which the Fermi gas is not fully equilibrated, as can occur when the system is driven at frequencies that exceed the rate of fermion backscattering. In this case, the Fermi gas is described by three bulk viscosities, which we obtain for a generic single-particle dispersion.

Повышение энергоэффективности аппарата воздушного охлаждения при утилизации попутного нефтяного газа на нефтяных месторождениях

Associated petroleum gas (APG) is one of the most important raw materials for industrial petrochemistry. APG burning is accompanied by the release of large volumes of harmful substances into the atmosphere, which leads to the environmental degradation, destruction of non-renewable natural resources, and contributes to the development of negative planetary processes that have an extremely negative impact on the global climate. One of the priority tasks in solving the problem of APG utilization is its cooling, which leads to decreasing gas viscosity, reducing wear of equipment, less hydraulic losses, and the greater operation speed and productivity of the pipeline. Air coolers of gas (ACG) are heat exchangers, whose purpose is condensation of liquid and gaseous media, as well as gas cooling. The advantages of using ACG are saving the cooling water and reducing the waste water, as well as decreasing the labor costs for cleaning ACG. There have been considered the types of ACG and their features. In order to optimize and improve the energy efficiency of the associated gas air cooler, a unit was proposed for cleaning the finned surface of the air cooler heat exchange tubes by using hydraulic nozzles with a full spray cone and by spraying the ACG to increase efficiency. The proposed method will make it possible to safely transfer the gas through main pipelines, maintain the correct pressure inside the reservoir during underground injection, and also lead to the least equipment wear.

Transport in p -wave-interacting Fermi gases

The scattering properties of spin-polarized Fermi gases are dominated by p-wave interactions. Besides their inherent angular dependence, these interactions differ from their s-wave counterparts as they also require the presence of a finite effective range in order to understand the low-energy properties of the system. In this article we examine how the shear viscosity and thermal conductivity of a three-dimensional spin-polarized Fermi gas in the normal phase depend on the effective range and the scattering volume in both the weakly and strongly interacting limits. We show that although the shear viscosity and thermal conductivity both explicitly depend on the effective range near resonance, the Prandtl number which parametrizes the ratio of momentum to thermal diffusivity does not have an explicit interaction dependence both at resonance and for weak interactions in the low-energy limit. In contrast to s-wave systems, p-wave scattering exhibits an additional resonance at weak attraction from a quasi-bound state at positive energies, which leads to a pronounced dip in the shear viscosity at specific temperatures.

Continuum Models for Bulk Viscosity and Relaxation in Polyatomic Gases

Bulk viscosity and acoustic wave propagation in polyatomic gases and their mixtures are studied in the frame of one-temperature and multi-temperature continuum models developed using the generalized Chapman–Enskog method. Governing equations and constitutive relations for both models are written, and the dispersion equations are derived. In the vibrationally nonequilibrium multi-component gas mixture, wave attenuation mechanisms include viscosity, thermal conductivity, bulk viscosity, diffusion, thermal diffusion, and vibrational relaxation; in the proposed approach these mechanisms are fully coupled contrarily to commonly used models based on the separation of classical Stokes–Kirchhoff attenuation and relaxation. Contributions of rotational and vibrational modes to the bulk viscosity coefficient are evaluated. In the one-temperature approach, artificial separation of rotational and vibrational modes causes great overestimation of bulk viscosity whereas using the effective internal energy relaxation time yields good agreement with experimental data and molecular-dynamic simulations. In the multi-temperature approach, the bulk viscosity is specified only by rotational modes. The developed two-temperature model provides excellent agreement of theoretical and experimental attenuation coefficients in polyatomic gases; both the location and the value of its maximum are predicted correctly. One-temperature dispersion relations do not reproduce the non-monotonic behavior of the attenuation coefficient; large bulk viscosity improves its accuracy only in the very limited frequency range. It is emphasized that implementing large bulk viscosity in the one-temperature Navier–Stokes–Fourier equations may lead to unphysical results.

An Explicit Method for Estimating the Average Reservoir Pressure and Gas in Place Based on the Gas Property Polynomial Function

The fast and accurate determination of average reservoir pressure (ARP) and gas reserves is vital for the analysis and forecasting of gas well performance. An explicit and relatively rigorous method for estimating the ARP and gas in place, based on the dynamic material balance equation and the gas property polynomial function (GPPF), is presented to circumvent such drawbacks as high cost, empiricism, poor adaptability to variable production schedules, and the necessity for iteration processes, by which current approaches usually have been limited. The gas flow model is solved by introducing pseudofunctions and considering the compressibility effects of rock and irreducible water, and the pressure-rate correlations during boundary-dominated flow (BDF) which constitute the theoretical proofs of this method are derived from the superposition principle coupled with the constant rate solution. Production data under different production scenarios prove it effective. The error of estimation for formation pressure and gas reserves hardly ever goes beyond 4% given that the BDF condition is generally satisfied by the rate and bottom hole flowing pressure (BHP) data. We employ the GPPF to capture the nonlinear variations of gas viscosity andZ-factor, helpful to implement a quick conversion between pressure and pseudopressure and to solve the integral equation concerning pseudopressure and thus valid in overcoming the limitations of previous methods concerning pressure or pressure squared. The proposed methodology boasts its simpleness and practicability, which not only dispenses with iterations on pseudotime but also applies to various production systems of gas wells under constant BHP, constant rate, or variable BHP/variable rate conditions.

Effects of turbulent diffusion and back-reaction on the dust distribution around two resonant planets

ABSTRACT In evolved and dusty circumstellar discs, two planets with masses comparable to Jupiter and Saturn that migrate outwards while maintaining an orbital resonance can produce distinctive features in the dust distribution. Dust accumulates at the outer edge of the common gas gap, which behaves as a dust trap, where the local dust concentration is significantly enhanced by the planets’ outward motion. Concurrently, an expanding cavity forms in the dust distribution inside the planets’ orbits, because dust does not filter through the common gaseous gap and grain depletion in the region continues via inward drifting. There is no cavity in the gas distribution because gas can filter through the gap, although ongoing gas accretion on the planets can reduce the gas density in the inner disc. Such behaviour was demonstrated by means of simulations neglecting the effects of dust diffusion due to turbulence and of dust backreaction on the gas. Both effects may alter the formation of the dust peak at the gap outer edge and of the inner dust cavity, by letting grains filter through the dust trap. We performed high-resolution hydrodynamical simulations of the coupled evolution of gas and dust species, the latter treated as pressureless fluids, in the presence of two giant planets. We show that diffusion and backreaction can change some morphological aspects of the dust distribution but do not alter some main features, such as the outer peak and the expanding inner cavity. These findings are confirmed for different parametrizations of gas viscosity.

A New Interpretation of Gas Viscosity for Flow through Micro-Capillaries and Pores.

The Hagen-Poiseuille equation for gas flowhad never been derived theoretically; it is rather a simple analogy of the same for liquid flow, and "gas viscosity" is a measure for overall resistance to flow. In this work, experimental flow data for different gases through capillaries and porous media, reported in literature by different groups, including those measured and treated by Knudsen are treated with Hagen-Poiseuille equation, but taking "gas viscosity" as an adjustable parameter. It is found that, at constant temperature, there exists an unambiguous relation between the viscosity (µ) of a given gas, and the product of average pressure (Pav ) and capillary diameter (D). In addition, for Pav * D<0.01, a universal linear relation exists between µ/M0.5 (where M is molecular mass) for different gases and the parameter Pav * D. The new interpretation of gas viscosity avoids the differentiation of regimes into "Knudsen" and "viscous" flow as it is frequently done in literature. The concept can be applied to obtain a reliable data base for gas viscosities in different fields of applications, for example in microfluidic systems or the analysis of pore size distributions of filters and membranes by gas flow porometry.

Bulk Viscosity of Dilute Gases and Their Mixtures

In this work, we use the Green–Kubo method to study the bulk viscosity of various dilute gases and their mixtures. First, we study the effects of the atomic mass on the bulk viscosity of dilute diatomic gas by estimating the bulk viscosity of four different isotopes of nitrogen gas. We then study the effects of addition of noble gas on the bulk viscosity of dilute nitrogen gas. We consider mixtures of nitrogen with three noble gases, viz., neon, argon, and krypton at eight different compositions between pure nitrogen to pure noble gas. It is followed by an estimation of bulk viscosity of pure oxygen and mixtures of nitrogen and oxygen for various compositions. In this case, three different composition are considered, viz., 25% N2 + 75% O2, 50% N2 + 50% O2, and 78% N2 + 22% O2. The last composition is aimed to represent the dry air. A brief review of works that study the effects of incorporation of bulk viscosity in analysis of various flow situations has also been provided.

Evaluation of Liquid Loading in Gas Wells Using Machine Learning

The inevitable result that gas wells witness during their life production is the liquid loading problem. The liquids that come with gas block the production tubing if the gas velocity supplied by the reservoir pressure is not enough to carry them to surface. Researchers used different theories to solve the problem naming, droplet fallback theory, liquid film reversal theory, characteristic velocity, transient simulations, and others. While there is no definitive answer on what theory is the most valid or the one that performs the best in all cases. This paper comes to involve a different approach, a combination between physics-based modeling and statistical analysis of what is known as Machine Learning (ML). The authors used a refined ML algorithm named XGBoost (extreme gradient boosting) to develop a novel full procedure on how to diagnose the well with liquid loading issues and predict the critical gas velocity at which it starts to load if not loaded already. The novel procedure includes a combination of a classification problem where a well will be evaluated based on some completion and fluid properties (diameter, liquid density, gas density, liquid viscosity, gas viscosity, angle of inclination from horizontal (alpha), superficial liquid velocity, and the interfacial tension) as a “Liquid Loaded” or “Unloaded”. The second practice is to determine the critical gas velocity, and this is done by a regression method using the same inputs. Since the procedure is a data-driven approach, a considerable amount of data (247 well and lab measurements) collected from literatures has been used. Convenient ML technics have been applied from dividing the data to scaling, modeling and assessment. The results showed that a wellconstructed XGBoost model with an optimized hyperparameters is efficient in diagnosing the wells with the correct status and in predicting the onset of liquid loading by estimating the critical gas velocity. The assessment of the model was done relatively to existing correlations in literature. In the classification problem, the model showed a better performance with an F-1 score of 0.947 (correctly classified 46 cases from 50 used for testing). In contrast, the next best model was the one by Barnea with an F-1 score of 0.81 (correctly classified 37 from 50 cases). In the regression problem, the model showed an R2 of 0.959. In contrast, the second best model was the one by Shekhar with an R2 of 0.84. The results shown here prove that the model and the procedure developed give better results in diagnosing the well correctly if properly used by engineers.

An improved seismic fluid identification method incorporating squirt flow and frequency-dependent fluid-solid inversion

Joint inversion of seismic amplitude and frequency information for fluid discrimination works as a popular approach for reservoir fluid identification. However, ignorance of the factor caused by fluid flow and the viscosity of oil and gas in current frequency-dependent inversion approaches leads to the inaccuracy of oil and gas prediction. Therefore, based on squirt flow and viscoelastic theory, a new frequency-dependent viscoelastic squirt-flow fluid factor is established, which is compared with other conventional fluid factors to verify its advantages in fluid detection. In addition, a new linearized reflectivity equation related to frequency-dependent viscoelastic squirt-flow fluid factor is derived. Finally, to verify the feasibility of the new fluid factor in predicting oil/gas, a frequency-dependent elastic impedance inversion method is introduced. Synthetic data and field data examples find that frequency-dependent viscoelastic squirt-flow fluid factor can eliminate the interference of “false bright spots” in conventional fluid factors inversion and has a higher vertical resolution, which demonstrated the effectiveness and stability of our method in fluid prediction.

Computational Fluid Dynamic Simulation of Leakage Acoustic Waves Propagation Model for Gas Pipelines

When leakage occurs for natural gas pipelines, acoustic waves generated at the leakage point will propagate to both ends of the pipe, which will be measured and processed to detect and locate the leakage. When acoustic waves propagate in the gas, the amplitude will attenuate and the waveform will spread, which decides the installation distance of acoustic sensors. Therefore, computational fluid dynamic (CFD) simulation research on the acoustic wave propagation model is accomplished and verified by experiments to provide the foundation for the acoustic leak location method. The propagation model includes two parts: amplitude attenuation model and waveform spreading model. Both can be obtained by the established CFD simulation model. Additionally, the amplitude attenuation model can be verified by the experiments. Then, the simulation method is applied to conclude the propagation model under variable conditions, including different flow directions, Reynolds numbers, and diameters. Finally, the experimental demonstration of the leak location based on the propagation model is given. The results indicate that not only the gas viscosity but also the gas flow can influence the propagation model, and the leak location method based on the propagation model is effective. Conclusions can be drawn that CFD simulation on the propagation model for natural gas pipelines is an efficient way to carry out research and provide the theoretical basis for acoustic leak location method application.

Strain Sensor-Inserted Microchannel for Gas Viscosity Measurement.

Quantifying the viscosity of a gas is of great importance in determining its properties and can even be used to identify what the gas is. While many techniques exist for measuring the viscosities of gases, it is still challenging to probe gases with a simple, robust setup that will be useful for practical applications. We introduce a facile approach to estimating gas viscosity using a strain gauge inserted in a straight microchannel with a height smaller than that of the gauge. Using a constrained geometry for the strain gauge, in which part of the gauge deforms the channel to generate initial gauge strain that can be transduced into pressure, the pressure change induced via fluid flow was measured. The change was found to linearly correlate with fluid viscosity, allowing estimation of the viscosities of gases with a simple device.

Scientific school of non-equilibrium aeromechanics in Saint Petersburg State University

The review is devoted to the foundation and development of the scientific school of S. V. Vallander at the Leningrad (now St Petersburg) State University. The achievements of the scientific school in the development of the kinetic theory methods for modeling nonequilibrium flows, construction of rigorous self-consistent mathematical models of varying complexity for strong and weak deviations from equilibrium, and the use of the developed models in challenging problems of modern aerodynamics are discussed. Particular attention is paid to the study of non-equilibrium kinetics and transport processes in carbon dioxide, identification of key relaxation mechanisms of polyatomic molecules, derivation of physically based reduced hybrid models, and optimization of non-equilibrium flow numerical simulations using modern machine learning methods. Correct description of electronic excitation in the kinetics and transport processes, models of local equilibrium gas flows with multiple ionization, and features of modeling bulk viscosity in polyatomic gases are discussed.