The Development and Application of EOS-based VT Phase Behavior Calculation Algorithms in Petroleum Industry

The use of equation of state (EOS)-based phase behavior calculations is widespread in the petroleum industry, including the calculation of oil and gas reserves, production forecasting, and optimization of enhanced oil recovery (EOR) plans, surface separator design, and pipe flow calculation. The most commonly used method for providing phase behavior information is PT phase-equilibrium-calculation algorithms, which have been extensively studied for decades. However, simulation and engineering design of these processes using VT phase-equilibrium- calculation algorithms is sometimes more convenient than using conventional PT algorithms and has distinct advantages. The VT algorithm has been continuously improved over the last decade to ensure calculation accuracy, robustness, and efficiency, and it has been gradually applied in the petroleum industry. This article provides an overview of research findings in the field of EOS-based VT phase behavior calculation algorithms and their applications in oil and gas engineering. The Helmholtz-free-energy minimization approach, the Gibbs-free-energy minimization approach, and the nested approach based on the PT algorithm are three typical VT algorithm approaches discussed. The petroleum industry’s main applications of phase equilibrium calculation using the VT algorithm are described. Furthermore, some existing problems are identified, and several prospects for the application of the VT algorithm in the petroleum engineering field are presented. A critical review of the current state of the VT algorithm process, we believe, will fill the gap by shedding light on the process’s flaws and limitations, future development areas, and new research topics

SAFT Regimes and Laminar Burning Velocities : A Comparative Study of NH3+ N2+ O2and CH4+ N2+ O2Flames

Super adiabatic flame temperature (SAFT) is a distinctive phenomenon in the adiabatic flame where the local maximum temperature exceeds the adiabatic flame temperature. The flame temperatures exhibiting the extent of SAFT are difficult to measure with low uncertainties in experiments, while the laminar burning velocity also represents global flame features, thus could possibly be related to the SAFT. The present study investigated the SAFT regimes, laminar burning velocities (SL), and their relationships for the CH4+ O2+ N2and NH3+ O2+ N2flames over large equivalence (φ) and oxygen ratio (xO2) ranges. The laminar burning velocities were experimentally measured using the heat flux method at φ = 1.4-1.8 and xO2= 0.22-0.44, where some conditions have never been reported before in the literature. Comparisons were made with simulated SLresults using five CH4mechanisms and five NH3mechanisms, and none of them well reproduce all of the experimental data. From the simulation results, three CH4SAFT regimes (I, II, and III) and two NH3SAFT regimes (I and II) have been identified, among which regime III for CH4and regime II for NH3were found for the first time. The kinetic origins of these regimes were discussed, and different flame features regarding the flame temperature and dominant species were clarified. The relationship between the SAFT extent and the laminar burning velocity is revealed by equation derivation based on the classical flame theories, proving that a mechanism reproducing well the SLand its temperature dependence can at the same time yield accurate predictions of the SAFT. The present study also provided the most sensitive reactions in the SAFT predictions accompanied by the rate constant uncertainties, which can be helpful for further mechanism development since none of the mechanisms reproduces well the present SLexperimental data, let alone the SAFT extent

Study on the formation mechanisms of H2S by aquathermolysis of thiophene 噻吩水热裂解生成H2S实验研究

On the basis of H2S formation during gas injection and heat removal,the thiophene and 5 kinds of metal salts（ AlCl3,CaCl2,MgCl2,NiCl2,ZnCl2） of heavy oil containing sulfur model compounds are studied. The thermal simulation of thiophene is performed to study the mechanisms of the formation of H2S in thiophene aquathermolysis. The tests demonstrate that:（ 1） the addition of metal salts can effectively reduce the activation energy of the reaction and promote the formation of H2S; The quantity of metal cation charges determines the difficulty of the hydrothermal cracking reaction. The more the charge number is,the easier the reaction is. That is,the catalytic order of metal ions for thiophene is Al3+> Ni2+> Mg2+> Ca2+> Zn2+.（ 2） The concentration of metal salt determines the degree of reaction. The higher the concentration of metal ions is,the faster the reaction rate.（ 3） The reaction kinetics of metal salt and AlCl3,NiCl2,MgCl2,CaCl2,ZnCl2\ua0reaction system were investigated. The catalytic effect of metal salt was verified by kinetic parameters and the reaction kinetics parameters of different reaction systems were obtained. The reaction activation energies of the six reaction systems are in the order of 57. 31 kJ/mol,17. 18 kJ/mol,22. 33 kJ/mol,24. 38 kJ/mol,25. 18 kJ/mol and 32. 79 kJ/mol respectively

Uniqueness and similarity in flame propagation of pre-dissociated NH3 + air and NH3 + H2 + air mixtures : An experimental and modelling study

Ammonia (NH3) has attracted significant attention as a promising hydrogen carrier and a carbon-free alternative fuel. Partial dissociation could convert part of ammonia to H2 and N2 before injecting the fuel into a combustor, thus overcoming the low reactivity and high NOx emission problems during the NH3 combustion. The pre-dissociated NH3 + air mixture has unburnt species NH3, H2, O2, and N2, the same as more widely investigated NH3 + H2 + air flames, while similarities or differences between these two types of flames have not yet been investigated. In the present work, the laminar burning velocities of pre-dissociated NH3 + air flames at 1 atm and an initial temperature of 298 K have been measured and compared to the scarce data from the literature. Experiments were carried out using the heat flux method at varied dissociation ratio γ and equivalence ratio ϕ. Kinetic simulations were also performed using six recently published or updated mechanisms, while none of the tested mechanisms can accurately reproduce the present results for the pre-dissociated NH3 + air flames over the whole range of the covered conditions, even for those predicting well the NH3 + H2 + air flames. To understand this deficiency, flame temperatures for the two fuel systems were examined, as well as in-depth sensitivity analyses were carried out. Similar conditions between the pre-dissociated NH3 + air and the NH3 + H2 + air flames were found, and a new approach to identifying inconsistent experimental data obtained using the same experimental setup was also suggested and discussed

Molecular simulation on mechanism of thiophene hydrodesulfurization on surface of NiP

Hydrodesulfurization reaction, as the last step of hydrothermal cracking reaction, is of great significance for the reduction of viscosity and desulfurization of heavy oil. Based on Density Functional Theory and using Dmol3 module of Materials Studio, this research simulated the adsorption and hydrodesulfurization of thiophene on Ni 2 P (001) surface, and discussed the hydrodesulfurization reaction mechanism of thiophene on Ni 2 P (001) surface. It was found that the direct hydrodesulfurization of thiophene had more advantages than the indirect hydrodesulfurization of thiophene. Finally, the optimal reaction path was determined: C 4 H 4 S+H 2 →C 4 H 6