NEW REPORT AND SOFTWARE AVAILABLE FOR GAS COMPRESSIBILITY FACTORS

Natural-gas engineers now have two accurate methods to compute gas-compressibility factors as a result of the new AGA Report No. 8 (Compressibility and Super-compressibility for Natural Gas and Other Hydrocarbon Gases) and supporting software. The new methods reproduce state-of-the-art pressure-volume-temperature measurements with an uncertainty of less than 0.1% at a 95% confidence level over a broad range of temperature, pressure, and gas characteristics.

July 19, 1993

2 min read

STATE-OF-ART MEASUREMENTS

The new methods reproduce state-of-the-art pressure-volume-temperature measurements with an uncertainty of less than 0.1% at a 95% confidence level over a broad range of temperature, pressure, and gas characteristics.

A variety of input data may be used, including natural-gas composition, heating value, specific gravity or relative density, temperature, and pressure.

The 200-page report provides equations, parameters, uncertainty estimates, calculation flow diagrams, sample calculations, the computer code, and a program-utility package. The computer program listing and software may be readily incorporated into flow-computer equipment or accounting software. It also includes features that facilitate data I/O and data conversions.

WHO USES IT

The report and diskette should be useful to engineers involved in gas production, processing, transmission, and distribution in which high-quality PVT information is required.

AGA members may obtain a copy of the technical report and software from the association for $40; nonmembers, for $80.

The methods outlined in the report will also support implementation of the new flow-measurement practice described in AGA Report No. 3 (Orifice Metering of Natural Gas and Other Related Hydrocarbon Fluids).

Additionally, the equations and programs contained in Report 8 will form the basis of a forthcoming international standard.

Because of the research and cooperative efforts of Gas Research Institute, AGA, and a group of European gas companies (GERG), the GRI says that the International Standard Organization (ISO) will approve the Draft International Standard based on these methods as a new ISO Standard later this year.

MORE WORK

In continuing work, GRI is developing software based on the Report No. 8 equations to provide a variety of derivative thermophysical properties, such as enthalpies, entropies, heat capacities, sonic velocities, Joule-Thomson coefficients, and critical flow factors.

The software, expected to be available in late 1993, will be useful, says the GRI, in compressor operations and analysis, sonic-nozzle flow measurements, and CNG analysis and applications.