Natural Gas Flow Research Articles

Unconventional advanced oxidation technique: Evaporation liquid rate and phenolic compounds degradation evaluation and modelling/optimization process with CFD, RSM and ANNs

This study aims to develop unconventional advanced oxidation processes for managing phenolic effluents generated from thermochemical oxidation using Direct Contact Thermal Treatment (DiCTT) for liquid water reuse. The DiCTT system uses a stainless-steel reactor described by the combustion of natural gas and production of hydroxyl radicals (OH), which ensures its compact installation and application to offshore oil-exploration platforms where natural gas is accessible and space is limited. The oxidation of phenolic compounds is evaluated under atmospheric pressure, which controls the rate of evaporation of the phenol to the environment during the combustion step, and thus helps avoid incineration in the liquid phase. The efficiency of the process is studied as a function of three independent variables: natural gas flow rate (QGN, 2–4 m3.h−1), air excess (E, 10–50%), and recycling rate of the combustion gases (QRG, 0–100%). Optimal conditions identified for complete phenol degradation (>99%) and total organic carbon (TOC) conversion (>30%) for a given rate of evaporation for the liquid phase (less than11%) and effluent temperature (70–78 °C) were QGN = 4 m3.h−1, E = 10%, and QRG = 100%. For modelling and optimization of results, Computational Fluid Dynamics (CFD), Response Surface Method (RSM) and Artificial Neural Network (ANN) technique were used. These techniques have shown to be very promising in the prediction of contaminant degradation and in the optimization of this type of mechanism.

An anisotropic pore-network model to estimate the shale gas permeability

The permeability of shale is a significant and important design parameter for shale gas extraction. The shale gas permeability is usually obtained based on Darcy flow using standard laboratory permeability tests done on core samples, that do not account for different transport mechanisms at high pressures and anisotropic effects in shales due to nano-scale pore structure. In this study, the permeability of shale is predicted using a pore network model. The characteristics of pore structure can be described by specific parameters, including porosity, pore body and pore throat sizes and distributions and coordination numbers. The anisotropy was incorporated into the model using a coordination number ratio, and an algorithm that was developed for connections of pores in the shale formation. By predicting hydraulic connectivity and comparing it with several high-pressure permeability tests, the proposed three-dimensional pore network model was verified. Results show that the prediction from the anisotropic pore network model is closer to the test results than that based on the isotropic pore network model. The predicted permeability values from numerical simulation using anisotropic pore network model for four shales from Qaidam Basin, China are quite similar to those measured from laboratory tests. This study confirmed that the developed anisotropic three-dimensional pore network model could reasonably represent the natural gas flow in the actual shale formation so that it can be used as a prediction tool.

Density and Electrical Conductivity for Aqueous Mixtures of Monoethylene Glycol and Sodium Chloride: Experimental Data and Data-Driven Modeling for Composition Determination

Monoethylene glycol (MEG) is a gas hydrate inhibitor widely applied for natural gas flow assurance. A series of density and electrical conductivity measurements of water + MEG + NaCl mixtures are reported, allowing the supervision of the MEG regeneration unit. Density (509 data points) and electrical conductivity (212 data points) measurements were performed in wide ranges of temperature, T = 278.15−363.15 K, and concentration of solvents and NaCl up to almost saturation. The theory of solutions was applied for density description using excess volume, which was correlated with the Redlich−Kister equation. The resulting absolute and relative mean deviations are 0.00127 g·cm−3 and 0.12%, indicating accurate representation. A semi- empirical correlation with 15 adjustable parameters was considered for electrical conductivity of water + MEG + NaCl mixtures. The obtained absolute and relative mean deviations are 1.49 mS·cm−1 and 5.70%. The properties functions presented an approximately orthogonal behavior to each other, allowing the determination of mixture composition from experimental density and electrical conductivity data. The Matlab environment was found to be robust in solving the nonlinear system of two equations with constraints. The proposed methodology was extensively tested, and deviations less than 0.0060 and 0.0011 in solvents and NaCl mass fractions were obtained, respectively, demonstrating the required accuracy for industrial application

Fluid dynamic analysis of liquefied natural gas flow through a cryogenic ball valve in liquefied natural gas receiving stations

Cryogenic ball valves are one of the most important fluid control devices in liquefied natural gas (LNG) receiving stations. The dynamic flow characteristics of cryogenic ball valves directly affect the stability of a pipeline system. In this paper, the sliding mesh technology was adopted to simulate the dynamic flow characteristics inside the cryogenic ball valve. Firstly, the energy loss inside the cryogenic ball valve during the opening and closing process was analyzed. It is found that the energy loss is larger when the spool degree is less than 30°, while the fluid resistance is very small at the rest of the degree. Then, the dynamic flow characteristics of the cryogenic ball valve at different spool rotational speeds were investigated. It is found that the velocity value and the flow turbulence are gradually increased when the spool rotational speed increases from 1.25 deg/s to 10 deg/s. Finally, dynamic flow characteristics during the valve opening process with fluctuation of inlet velocity were analyzed. It is found that the distribution of velocity and pressure is approximately consistent, while the value of velocity and pressure is increased with the increase of inlet velocity. It is helpful for the design of cryogenic ball valves and the improvement of the whole LNG pipeline system.

Assessment the gas potential of coal-bearing mudstones from upper paleozoic in ordos basin via gold-tube pyrolysis

Previous natural gas explorations in Ordos Basin were conducted in areas with thick coal deposited. Recently, natural gas flow were discovered in southern basin where very thin coal seams were developed, implying the contribution from other source rocks, e.g. the coal measure mudstones. In order to thoroughly assess the quality and gas potential of coal measure mudstones, 58 mudstones from borehole were analyzed by Rock-Eval method and gold-tube pyrolysis was carried out on immature carbonaceous and dark mudstones with detailed geochemical characteristics of hydrocarbon products detected.The results indicated the mudstones were dominated by type III kerogen and assisted by type II kerogen and were fair to good source rocks. Pyrolysis data demonstrated the peak yield of C1-5 for carbonaceous mudstone was very close to that of coal, whereas the maximum C1-5 yield for dark mudstone accounted for 62.5% of that of carbonaceous mudstone, indicating the good gas potential of carbonaceous mudstone. The generated gaseous hydrocarbons were predominately derived from primary kerogen cracking.The computed activation energy of C1-5 for carbonaceous mudstone showed a more discrete distribution compared to dark mudstone. The modeled methane conversion for dark mudstone was higher than that of carbonaceous mudstone since entering main gas generation stage, which was consistent with the concentrated and lower activation energies for dark mudstone. Furthermore, the modeled gas in southern basin was much higher than that in central basin, due to the more severe thermal alteration that coal measures in southern basin had experienced.On the basis of the integrated analysis of methane generation and adsorption, the areas with thick carbonaceous mudstone deposited had fair exploration prospects and further gas explorations should pay more attention on.

Key influence factors on suspension compressible fluid through pore induced by SAW (motion of black powder in pipeline)

The flow of compressible fluid with suspended particles in circular tube under the effect of surface acoustic wave (SAW) is investigated. The system of differential equations for both the fluid and particles phases is solved using the perturbation method to simplify the system of equations. The time average of flow rate is calculated, and the effect of Reynolds number, wave number, concentration and density ratio is studied. Comparison between our study and the previous is discussed. The effect of SAW on the flow of suspended natural gas is taken as an application. Real data are used to introduce this application. The SAW on pipeline may avoid accumulation of black powder.

Impact of Heavy Hydrocarbon Concentration on Natural Gas Flow through Transportation Pipelines

In this work, binary, ternary, quaternion, and quinary natural gas mixtures were evaluated including methane, ethane, propane, butane, and pentane to highlight their impact on pipeline performance and thermophysical properties of natural gas. The results presented that all the heavy hydrocarbons have a negative impact on natural gas phase envelope. For binary mixtures, methane/propane recorded the widest two-phase envelopes while the quinary mixtures generally formed the widest two-phase envelopes over the other mixtures. Besides, the heavy hydrocarbons content of different mixtures increased the critical pressures and critical temperatures in comparison to pure methane. The highest temperature drop of 6.495 °C was recorded by the binary mixture and the lowest temperature drop of 6.341 °C was by quinary mixture. The highest pressure drop of 4.964 bars was caused by the quinary mixture, while the lowest pressure drop of 4.1 bars was by the binary mixture. In addition, the results showed that natural gas density controlled by methane content caused increasing the methane content resulting in reducing the density of natural gas mixture. The viscosity of natural gas is a sensitive parameter to the content of the heavy hydrocarbon concentrations and all heavy hydrocarbons increased the viscosity of natural gas in comparison to pure methane.

A basic model of unconventional gas microscale flow based on the lattice Boltzmann method

A new method for selecting dimensionless relaxation time in the lattice Boltzmann model was proposed based on similarity criterion and gas true physical parameters. At the same time, the dimensionless relaxation time was modified by considering the influence of the boundary Knudsen layer. On this basis, the second-order slip boundary condition of the wall was considered, and the key parameters in the corresponding combined bounce-back/specular-reflection boundary condition were deduced to build a new model of unconventional gas microscale flow simulation based on the lattice Boltzmann method suitable for high temperatures and high pressures. The simulation results of methane gas flow driven by body force in infinite micro-channels and flow driven by inlet-outlet pressure differential in long straight channels were compared with the numerical and analytical solutions in the literature to verify the accuracy of the model, and the dimensionless relaxation time modification was formally optimized. The results show that the new model can effectively characterize the slippage effect, compression effect, gas density and the effect of boundary Knudsen layer in the micro-scale flow of unconventional natural gas. The new model can achieve a more comprehensive characterization of the real gas flow conditions and can be used as a basic model for the simulation of unconventional gas flow on the micro-nano scale.

Interoperability of LNG terminals and gas pipeline networks

The interchangeability between natural gas of different sources and LNG have been concerned and tackled to a certain extent at home, and the interconnection of gas infrastructures including LNG terminals and gas pipeline networks have also been lifted up to the national level since 2018. However, the research on the interoperability with overall-planning interchangeability and interconnection at a higher level is still in the blank stage at home. By extensively investigating EU's regulations and practices related to interoperability in the field of natural gas pipeline network, this paper put forward the conceptual definition of the interoperability of gas infrastructures including LNG terminals and gas pipeline networks for the first time. Then, the basic implementation framework and components of interoperability were set up. Finally, domestic latest typical cases which have presented the characteristics of interoperability in the recent two years were analyzed. And the following research results were obtained. First, interoperability and third-party access are two independent themes. Second, the target of interoperability is to realize the cross-system unimpeded flow of natural gas of all facility users between different facilities according to the uniform specification of specific technical standards, operation criteria and operation procedures of various facilities, based on interconnection, coordination and information interaction. Third, the framework of interoperability consists of 8 key elements, including gas quality standard & interchangeability, facility interconnection, facility interconnection agreement, unified measurement unit, unified electronic data exchange platform, technical capacity calculation method, approval procedure of LNG carrier entering the port and ship–shore compatibility unique to LNG terminals, and gas quality based LNG storage and tank loading rules. Fourth, it is recommended to give consideration to both target and requirement of interoperability and fully integrate 3 elements that are discussed more deeply and more crucial in EU countries (i.e., facility interconnection agreement, unified electronic data exchange platform and technical capacity calculation method) into the practice system of treatment reform of domestic natural gas industry chain.

Influence of reservoir-scale heterogeneities on the growth, evolution and migration of a CO2 plume at the Sleipner Field, Norwegian North Sea

New analysis of the baseline (pre-injection) seismic data at Sleipner has revealed large-scale, roughly north-trending, channelled ‘fairways’ at a range of stratigraphical levels in the Utsira Sand. The baseline data also reveal localised stratigraphical ‘point discontinuities’ within the reservoir, some of which show evidence of having provided vertical conduits for earlier natural gas flow. The repeat time-lapse seismic datasets, where finer details of reservoir geology are illuminated by the reflective CO2, show smaller-scale, north-trending and sometimes sinuous channels within the larger channel fairways. They also show a number of vertical CO2 pathways within the CO2 plume, corresponding to the point discontinuities seen on the baseline data.Reservoir flow models were set up with flow properties constrained only by the observed levels of CO2 accumulation in the reservoir and the arrival time of CO2 at the reservoir top just prior to the first repeat seismic survey in 1999. The initial model with laterally homogeneous sand units separated by thin semi-permeable mudstones achieved only a moderate match to the observed time-lapse seismic data. Subsequent flow models, progressively incorporating higher permeability vertical CO2 pathways through the mudstones and large-scale channel fairways within the reservoir sands, yielded a progressive and marked improvement in the history-match of key CO2 layers within the plume. Crucially, no layer-specific model calibration was employed to achieve this improvement.New geophysical measurements from Utsira Sand core have recently become available. These measurements provide important constraints on rock physics models of CO2 and brine mixtures in the Utsira Sand. An empirical Brie fluid mixing law for intermediate fluid saturations provides a good fit to the new laboratory data, allowing measurements of CO2 saturation to be converted into seismic velocity. This rock physics model was used to convert CO2 saturation distributions predicted by the most realistic reservoir model into a seismic velocity model of the CO2 plume. Synthetic seismic reflectivity profiles generated using this velocity model show a striking resemblance to the observed time-lapse seismic data, both in terms of plume layer reflectivity and also of time-shifts within and beneath the CO2 plume. This provides confidence in the fidelity of the preferred reservoir model solution.These results represent a significant breakthrough in the understanding and modelling of CO2 plume development at Sleipner. We emphasise that the improvements were brought about not by fine tuning reservoir properties to fit the observed time-lapse data, but simply by incorporating geological permeability features that can reasonably be inferred from the baseline seismic data.

Numerical Study on Flow and Heat Transfer Performance of Natural Gas in a Printed Circuit Heat Exchanger During Transcritical Liquefaction

Abstract The main cryogenic heat exchanger is a core piece of equipment in the liquefaction of natural gas. The printed circuit heat exchanger is gradually becoming a primary choice for the main cryogenic heat exchanger, because it has good pressure resistance, high efficiency, and compactness. In this work, a numerical simulation is conducted to examine the local flow and heat transfer characteristics of natural gas in the printed circuit heat exchanger during trans-critical liquefaction. It is found that the heat flux density reaches a minimum value and the heat transfer is the worst when the temperature difference between the hot and cold sides is the smallest. Owing to the large variations in physical properties of trans-critical natural gas, the local pressure drop exhibits an upward parabolic shape along the flow direction, and the pressure drop reaches a minimum value near the pseudo-critical point. Finally, the friction factor and heat transfer correlations for natural gas during trans-critical liquefaction are fitted.

Effect of Radiative Filling Gas in Compound Parabolic Solar Energy Collectors

In the present paper, the use of radiating gas instead of air inside the cavity of compound parabolic collectors (CPSs) is suggested and verified by numerical analysis. The collector under study has a simple cone shape with flat absorber which is filled with a participating gas such as carbon dioxide instead of air for the purpose of increasing the thermal performance. In numerical simulation, the continuity, momentum and energy equations for the steady natural convection laminar gas flow in the CPC’s cavity and the conduction equation for glass cover and absorber plate were solved by the finite element method (FEM) using the COMSOL multi-physics. Because of the radiative term in the gas energy equation, the intensity of radiation in participating gas flow should be computed. Toward this end, the radiative transfer equation (RTE) was solved by the discrete ordinate method (DOM), considering both diffuse and collimated radiations. The approximation was employed in calculation of the diffuse part of radiation. It was observed that the gas radiation causes high temperature with more uniform distribution inside the cavity of collector. Also, numerical results reveal more than 3% increase in the rate of heat transfer from absorber surface into working fluid and hence a desired performance for the collector because of the gas radiation effect. Comparison between the present numerical results with theoretical and experimental data reported in the literature showed good consistency.

Case study on diagnosis and identify the degree of bottom hole liquid accumulation in double-branch horizontal wells in PCOC

In the process of continuous production of natural gas wells, formation pressure and gas flow rate decrease continuously. The ability to carry liquid decreases continuously, thus gradually forming bottom hole liquid. Bottom hole liquid accumulation is an important reason for the decrease of production or shutdown of natural gas wells. How to diagnose whether there is liquid accumulation in natural gas wells and identify the degree of liquid accumulation, to adopt drainage gas recovery operation in time, is the research focus of efficient development of natural gas reservoirs. In this paper, a method for diagnosing bottom hole liquid accumulation combining production performance curve and modified Fernando inclined well critical liquid-carrying model is designed for a large scale double-branch horizontal well used in unconventional reservoirs. The method is applied to the Well X2 of He 8 Member in PCOC. The application results showed that there was no liquid accumulation in the horizontal and vertical sections of the Well X2. The liquid in the wellbore was generated at the bottom of the inclined section and the liquid accumulation is upward along the wellbore from the bottom of the inclined section, with the height of 3 m.

Analysis of a model of a natural gas pipeline—a transfer function approach

Abstract A framework for natural gas pipelines is developed in a context similar to the theory of electric transmission lines. The system of semi-linear partial differential equations describing the time-dependent flow of natural gas is linearized around the steady-state flow. Additional approximations lead to a constant coefficient linear system that is equivalent to an electrical circuit that is analytically solvable and admits an ABCD matrix representation of input and output. The sinusoidal steady-state operation of natural gas pipelines is analysed including the distortion of waves. It is shown that the timing of the propagation of phases and other events is accurately represented in the approximation. The quantitative accuracy for flux and gas density of the approximation depending on different operating scenarios and depending on the frequency of the disturbances is documented.

Fast-acting shut-off and control ball valve application for control of gas flow rate to power plant boilers

The work describes the design and algorithms for controlling the fast-acting shut-off and control ball valve calculation of the reliability of the natural gas flow control system for the power plant boiler. Its application makes it possible to improve the quality of fuel combustion control, as well as to reduce the quantity of shut-off and control valves of gas channel, which in turn also leads to improvement of reliability of the system as a whole.

The Variational Bayesian Inference for Network Autoregression Models

We develop a variational Bayesian (VB) approach for estimating large-scale dynamic network models in the network autoregression framework. The VB approach allows for the automatic identification of the dynamic structure of such a model and obtains a direct approximation of the posterior density. Compared to Markov Chain Monte Carlo (MCMC) based sampling approaches, the VB approach achieves enhanced computational efficiency without sacrificing estimation accuracy. In the simulation study conducted here, the proposed VB approach detects various types of proper active structures for dynamic network models. Compared to the alternative approach, the proposed method achieves similar or better accuracy, and its computational time is halved. In a real data analysis scenario of day-ahead natural gas flow prediction in the German gas transmission network with 51 nodes between October 2013 and September 2015, the VB approach delivers promising forecasting accuracy along with clearly detected structures in terms of dynamic dependence.

Numerical Simulation of Conjugate Heat Exchange at Gas Flowing in a Well

A mathematical model is offered for conjugate heat exchange when gas flows in the section of a vertical well. The motion of the medium is described using a two-dimensional axisymmetric stationary formulation based on boundary-layer equations. The turbulent gas flowing due to the reservoir energy is considered. Natural gas is taken as a travelling medium. The numerical simulation results are presented in the form of the dependences of the flow temperature and gas density along the radius of the well on the external factors of the heat exchange changing along the well height. The results describe the thermobaric state of the well in the condition of the conjugate heat exchange of the produced natural gas flow and tubed well depending on the external thermal conditions.

Aerodynamics and Heat Transfer of Swirling Natural Gas Flow in a Vortex Heat Exchanger of the Heating System of a Gas Control Point

Purpose of research. To obtain a two-parameter model characterizing the aerodynamic and heat exchange processes occurring in a vortex heat exchanger, giving a better agreement between the calculated and experimental values of the heat transfer coefficient taking into account the curvature of the swirling gas flow in a vortex heat exchanger, in which a controlled gas pressure drop is used as a source of thermal energy. This technical solution will make it possible to abandon the installation of autonomous sources of thermal energy, which will reduce the cost of gas as a fuel in the heating system of the industrial premises of the gas distribution point (GDP), as well as provide more comfortable working conditions for the hydraulic fracturing pressure regulator. Methods. Comprehensive analysis of thermal and hydraulic characteristics in a vortex heat exchanger is based on well-known theoretical positions and equations of motion of a swirling gas flow and heat exchange laws. Results. It is obtained a dependence that characterizes the intensification of heat transfer based on the influence of the axial and rotational speed, as well as the path of motion of the swirling gas flow. This dependence is obtained on the basis of a comprehensive analysis of the aerodynamic and heat exchange characteristics of a vortex heat exchanger, in which a controlled gas pressure drop is used as a source of thermal energy. Conclusion. The obtained two-parameter model gives the best agreement of the calculated values of the heat transfer coefficient with the values obtained experimentally, which were used in the thermal engineering calculation of the design parameters of the vortex heat exchanger.

Modelling of autonomous power source for gas distribution station using ASPEN HYSYS

The article is devoted to the study of energy conservation issues in gas transmission and gas distribution systems. In the Aspen HYSYS software package, the authors developed a model of an autonomous power source for gas distribution station (GDS). A brief simulation sequence is described. The dependence of the electric power of the expander-generator unit on the natural gas flow ratio is determined.

Blow-down calibration of a large ultrasonic flow meter

Oil and gas production industries use large (diameter > 0.8 m) ultrasonic flow meters (USMs) to measure exhaust gas from flare stacks, emissions from smokestacks, flow of natural gas, etc. Since most flow laboratories do not have compressors with sufficient flow capacity (>10 kg/s) to calibrate large flow meters, calibrations are performed using the blow-down method where flow is generated by discharging high pressure tanks, leading to significant flow transients. We used an array of critical flow venturis (CFVs) in a blow-down facility to calibrate a large (D = 89.5 cm) 8-path ultrasonic flow meter. The flow transients associated with the blow-down process caused large spatial and temporal variations in temperature that dominated (40%–67%) the uncertainty budget. Our uncertainty analysis accounts for transient-generated uncertainties and provides guidelines for improving blow-down calibrations of large flow meters.