Simplified Graphical Method of Determining Gas Compressibility Factors

10.2118/75-pa ◽  
1961 ◽  
Vol 13 (11) ◽  
pp. 1081-1082
Author(s):  
Leon Rice
Keyword(s):  
Graphical Method ◽  
Compressibility Factors ◽  
Gas Compressibility

scholarly journals Volumetric Measurements of Methane-Coal Adsorption and Desorption Isotherms—Effects of Equations of State and Implication for Initial Gas Reserves

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 2022 ◽  
Author(s):  
Jamiu M. Ekundayo ◽  
Reza Rezaee
Keyword(s):  
Bituminous Coal ◽  
Equations Of State ◽  
Hysteresis Loops ◽  
Desorption Isotherm ◽  
Model Parameters ◽  
Adsorbed Gas ◽  
Desorption Isotherms ◽  
Compressibility Factors ◽  
Gas Compressibility ◽  
Adsorption Curve

This study presents the effects of equations of state (EOSs) on methane adsorption capacity, sorption hysteresis and initial gas reserves of a medium volatile bituminous coal. The sorption experiments were performed, at temperatures of 25 °C and 40 °C and up to 7MPa pressure, using a high-pressure volumetric analyzer (HPVA-II). The measured isotherms were parameterized with the modified (three-parameter) Langmuir model. Gas compressibility factors were calculated using six popular equations of state and the results were compared with those obtained using gas compressibility factors from NIST-Refprop® (which implies McCarty and Arp’s EOS for Z-factor of helium and Setzmann and Wagner’s EOS for that of methane). Significant variations were observed in the resulting isotherms and associated model parameters with EOS. Negligible hysteresis was observed with NIST-refprop at both experimental temperatures, with the desorption isotherm being slightly lower than the adsorption isotherm at 25 °C. Compared to NIST-refprop, it was observed that equations of state that gave lower values of Z-factor for methane resulted in “positive hysteresis”, (one in which the desorption isotherm is above the corresponding adsorption curve) and the more negatively deviated the Z-factors are, the bigger the observed hysteresis loop. Conversely, equations of state that gave positively deviated Z-factors of methane relatively produced “negative hysteresis” loops where the desorption isotherms are lower than the corresponding adsorption isotherms. Adsorbed gas accounted for over 90% of the calculated original gas in place (OGIP) and the larger the Langmuir volume, the larger the proportion of OGIP that was adsorbed.

Modification of Hall-Yarborough Equation of State For Predicting Gas Compressibility Factors

2019 ◽  
Author(s):  
Ibrahim Ayuba ◽  
S. O. Isehunwa ◽  
M. B. Adamu ◽  
A. Usman ◽  
M. N. Bello
Keyword(s):  
Equation Of State ◽  
Compressibility Factors ◽  
Gas Compressibility

scholarly journals A Novel Simplification for the Prediction of Natural Gas Compressibility Factor

2021 ◽  
pp. 63-76
Author(s):  
OMOBOLANLE Oluwasegun Cornelious ◽  
AKINSETE Oluwatoyin Olakunle ◽  
AROMOKEYE Niyi
Keyword(s):  
Natural Gas ◽  
Compressibility Factor ◽  
Reservoir Properties ◽  
Predictive Tool ◽  
Deviation Factor ◽  
Temperature And Pressure ◽  
Explicit Correlation ◽  
Compressibility Factors ◽  
Gas Compressibility ◽  
Reduced Temperature

The need for a simpler, effective and less expensive predictive tool for the estimation of natural gas compressibility factor cannot be exaggerated. An accurate prediction of gas compressibility factor is essential because it plays a definitive role in evaluating gas reservoir properties used in the estimation of gas reserves, custody transfer and design of surface equipment. In this present work, a novel explicit correlation and a highly sophisticated computer program were developed to accurately predict natural gas deviation factor. The research also aims to effectively capture the relationship between Pseudo-reduced temperature and pressure in relations to the Z-factor. In this study, 3972 digitized data points extracted from Standing and Katz’s Chart were regressed and analyzed using Microsoft Excel Spreadsheet, the extraction of this data was done using WebPlotDigitizer developed by Ankit Rohatgi of GitHub, Pacifica, CA, USA. The correlation was developed as a function of Pseudo-reduced temperature and pressure with tuned parameters distributed across 1.05 ≤ Tpr ≤ 3.0 and 0 < Ppr ≤ 8.0. Subsequently, the input (Tpr and Ppr values) of the feed data was used to validate the correlation and compare it with other known and published correlations. Statistical analysis of the results showed that a 99.8% agreement exists between the predicted and actual compressibility factors for the various test scenarios and case studies involving both sweet and sour gases. Also, the correlation was observed to outperform other models. Finally, the results were observed to perfectly mimic the Standing and Katz charts with an overall correlation coefficient of 99.76% and an adjusted R2 of 99.75%. The proposed correlation was subsequently used to develop a software using JavaScript. Undoubtedly, the proposed correlation and software are suitable for rapid and accurate simplification and prediction of natural gas compressibility factor.

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