The article develops and analyzes a method of the comprehensive evaluation of the quality of natural gas as an energy source. The method is based on establishing the calorific value of natural gas as a determinative index of its quality, taking into account all gas properties: both those that positively affect the gas calorific value and its energy content, and those that adversely affect. The generalized definition of natural gas quality as the degree to which the set of the own gas characteristics (component composition and physical properties) meet the requirements concerning energy content, safety, ecology, and other factors is given. The results of experimental researches on natural gas quality according to the developed procedure are also presented.

The article considers the current methods of measuring the calorific value of natural gas which are valid in the upto-date gasometry. The procedure for measuring the gross and net volume-basis specific calorific value of natural gas by the calorimetric method is analyzed. It is shown that to increase the accuracy and validity of measurement results, the experiment to determine the values of gross and net volume-basis specific calorific should be performed for at least 5 samples of the investigated gas. A methodology for estimating the accuracy of measuring the gross and net volume-basis specific calorific values of natural gas by the calorimetric method by finding estimates of the uncertainty of the obtained measurement results taking into account both random and systematic influencing factors are developed. The uncertainty budgets for measuring the gross and net volumebasis-specific calorific values of natural gas have been developed for the practical implementation of the methodology. The results of experimental studies of samples of one of the natural gas fields are given and the objective values of the gross and net volumebasis specific calorific with estimates of extended uncertainty are obtained.