scholarly journals COMPARATIVE STUDY OF EMPIRICAL CORRELATIONS AND EQUATIONS OF STATE EFFECTIVENESS FOR COMPRESSIBILITY FACTOR OF NATURAL GAS DETERMINATION

2021 ◽  
Vol 18 (38) ◽  
pp. 188-213
Author(s):  
Victor L. MALYSHEV ◽  
Yana F. NURGALIEVA ◽  
Elena F. MOISEEVA
Keyword(s):  
Equation Of State ◽  
Natural Gas ◽  
Equations Of State ◽  
Compressibility Factor ◽  
Gas Mixtures ◽  
Empirical Correlations ◽  
Shift Parameter ◽  
Reduced Pressure ◽  
Absolute Relative Error ◽  
Average Absolute Relative Error

Introduction: Today, there are four main groups of methods for calculating the compressibility factor of natural gas: experimental measurements, equations of state, empirical correlations, modern methods based on genetic algorithms, neural networks, atomistic modeling (Monte Carlo method and molecular dynamics). A correctly chosen method can improve the accuracy of calculating gas reserves and predicting its production and processing. Aim: To find the optimal methods for calculating the z-factor following the characteristic thermobaric conditions. Methods: To determine the best method for calculating the compressibility factor, the effectiveness of using various empirical correlations and equations of state to predict the compressibility factor of hydrocarbon systems (reservoir gases and separation gases) of various compositions were evaluated by comparing numerical results with experimental data. Results and Discussion: Based on 824 experimental values of the compressibility factor for 235 various gas mixtures in the pressure range from 0.1 to 94 MPa and temperatures from 273 to 437 K, the optimal equation of state and empirical correlation dependence for accurate z-factor prediction was found. It is shown that for all gas mixtures the Peng-Robinson equation of state with the shift parameter and Brusilovsky equation of state allow achieving best results. For these methods, the average absolute relative error does not exceed 2%. Among the correlation dependences, the best results are shown by the Sanjari and Nemati Lay; Heidaryan, Moghadasi and Rahimi correlations with an error not exceeding 3%. Conclusions: It was found that for the proposed methods, the reduced pressure has a more significant effect on the accuracy of the calculated values than the reduced temperature. It is shown that when studying acid gas mixtures with a carbon dioxide content of more than 10%, the equations of state better describe the phase behavior of the system in comparison with empirical correlations.

Technique and results of experimental determination of the compressibility factor of the natural gas

2021 ◽  
pp. 35-40
Author(s):  
Denis Y. Kutovoy ◽  
Igor A. Yatsenko ◽  
Vladimir B. Yavkin ◽  
Aydar N. Mukhametov ◽  
Petr V. Lovtsov ◽  
...  
Keyword(s):  
Natural Gas ◽  
Equations Of State ◽  
Compressibility Factor ◽  
High Accuracy ◽  
State Equations ◽  
Actual Problem ◽  
Temperature Range ◽  
Relative Value ◽  
Compressibility Coefficient

The actual problem of the possibility of using the equations of state for the gas phase of natural gas at temperatures below 250 K is considered. To solve it, the compressibility coefficients of natural gas obtained experimentally with high accuracy are required. The technique was developed and experimental study was carried out of compressibility factor aiming expanding temperature range of the state equations GERG-2004 and AGA8-DC92. The proposed technique is based on the fact that to assess the applicability of the equation of state, it is sufficient to obtain the relative value of the compressibility coefficient and not to determine its absolute value. The technique does not require complex equipment and provides high accuracy. The technique was tested on nitrogen, argon, air and methane. Uncertainty of determination of the compressibility factor is not greater than 0.1 %. For two different compositions of natural gas, obtained experimental data were demonstrated that the equations of state GERG-2004 and AGA8-92DC provide uncertainty of the calculation of the compressibility coefficient within 0.1 % in the temperature range from 220 K to 250 K and pressure below 5 MPa.

A Comparison Between PSRK and GERG-2004 Equation of State for Simulation of Non-Isothermal Compressible Natural Gases Mixed with Hydrogen in Pipelines / Porównanie równań stanu opracowanych według metody PSRK oraz GERG-2004 wykorzystanych do symulacji zachowania ściśliwych mieszanin gazu ziemnego i wodoru w rurociągach, w warunkach przepływów nie-izotermicznych

2013 ◽  
Vol 58 (2) ◽  
pp. 579-590
Author(s):  
Frits E. Uilhoorn
Keyword(s):  
Equation Of State ◽  
Natural Gas ◽  
Gas Flow ◽  
Transient Flow ◽  
Equations Of State ◽  
Group Contribution Method ◽  
Flow Conditions ◽  
Fluid Approximation ◽  
Natural Gases

In this work, the GERG-2004 equation of state based on a multi-fluid approximation explicit in the reduced Helmholtz energy is compared with the predictive Soave-Redlich-Kwong group contribution method. In the analysis, both equations of state are compared by simulating a non-isothermal transient flow of natural gas and mixed hydrogen-natural gas in pipelines. Besides the flow conditions also linepack-energy and energy consumption of the compressor station are computed. The gas flow is described by a set of partial differential equations resulting from the conservation of mass, momentum and energy. A pipeline section of the Yamal-Europe gas pipeline on Polish territory has been selected for the case study.

Measurement of Decompression Wave Speed in Rich Gas Mixtures at High Pressures (370 bars) Using a Specialized Rupture Tube

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
K. K. Botros ◽  
J. Geerligs ◽  
R. J. Eiber
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Wave Speed ◽  
High Pressures ◽  
Equations Of State ◽  
Gas Mixtures ◽  
Internal Diameter ◽  
Decompression Wave ◽  
Predicted Values ◽  
Fracture Arrest

Measurements of decompression wave speed in conventional and rich natural gas mixtures following rupture of a high-pressure pipe have been conducted. A high-pressure stainless steel rupture tube (internal diameter=38.1 mm and 42 m long) has been constructed and instrumented with 16 high frequency-response pressure transducers mounted very close to the rupture end and along the length of the tube to capture the pressure-time traces of the decompression wave. Tests were conducted for initial pressures of 33–37 MPa-a and a temperature range of 21–68°C. The experimentally determined decompression wave speeds were compared with both GASDECOM and PIPEDECOM predictions with and without nonequilibrium condensation delays at phase crossing. The interception points of the isentropes representing the decompression process with the corresponding phase envelope of each mixture were correlated with the respective plateaus observed in the decompression wave speed profiles. Additionally, speeds of sound in the undisturbed gas mixtures at the initial pressures and temperatures were compared with predictions by five equations of state, namely, BWRS, AGA-8, Peng–Robinson, Soave–Redlich–Kwong, and Groupe Européen de Recherches Gaziéres. The measured gas decompression curves were used to predict the fracture arrest toughness needed to assure fracture control in natural gas pipelines. The rupture tube test results have shown that the Charpy fracture arrest values predicted using GASEDCOM are within +7% (conservative) and −11% (nonconservative) of the rupture tube predicted values. Similarly, PIPEDECOM with no temperature delay provides fracture arrest values that are within +13% and −20% of the rupture tube predicted values, while PIPEDECOM with a 1°C temperature delay provides fracture arrest values that are within 0% and −20% of the rupture tube predicted values. Ideally, it would be better if the predicted values by the equations of state were above the rupture tube predicted values to make the predictions conservative but that was not always the case.

Prediction of Sound Speed in Natural-Gas Mixtures Using the CP-PC-SAFT Equation of State

2020 ◽  
Vol 54 (6) ◽  
pp. 1267-1275
Author(s):  
I. V. Prikhod’ko ◽  
A. A. Samarov ◽  
A. M. Toikka ◽  
M. Farzaneh-Gord
Keyword(s):  
Equation Of State ◽  
Natural Gas ◽  
Sound Speed ◽  
Gas Mixtures
Sign in / Sign up

Export Citation Format

Share Document