Abstract

Previous gas well test analyses have been based mainly upon linearizationsof ideal gas flow results, although a method for drawdown analysis based uponreal gas flow results has been proposed. Linearizations based upon ideal gasflow require estimation of gas physical properties at some sort of averagepressure, and implicitly involve the assumption that pressure gradients aresmall everywhere in the reservoir. A new real gas flow equation has beendeveloped by means of a substitution which couples pressure, viscosity and gaslaw deviation factor. This substitution has been called the real gaspseudo-pressure. Use of the real gas pseudo-pressure leads to simple equationsdescribing real gas flow which do not contain pressure-dependent gasproperties, and which do not require the assumption of small pressure gradientseverywhere in the flow system.

Equations required to determine flow capacity, well condition and staticformation pressure from pressure drawdown and build-up tests with the real gaspseudo-pressure concept are presented. Also shown are applications of the realgas pseudo-pressure to back-pressure testing, the gas materials balance andrigorous determination of average gas properties for previous gas flowequations. Included are sample calculations for well test analyses.

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