Development of reference materials for gas permeability

The article presents the development of reference materials of gas permeability of rocks (imitators) with traceability to Get 210–2019: State Primary Standard of Units of Specific Adsorption of Gases, Specific Surface Area of Pores, Specific Volume of Pores, Dimension of Pores, Open Porosity, and Coefficient of Gas Permeability of Solid Substances and Fabricated Materials. At the time of the beginning of this study, in the system of metrological assurance of gas permeability coefficient measurements, there were only reference materials of an approved type with traceability to the measurement results obtained in an interlaboratory experiment using gas permeability analyzers that were calibrated using the same reference materials, and reference materials with traceability to the State Primary Standard were absent. As a result, in the metrological practice of gas permeability measurement, there was no stable basis for comparison. This fact prompted the authors to research work in this area. The article considers the key stages of the process of reference materials development: analysis of similar reference materials of an approved type, selection of the starting material for reference materials, performing experimental research, and determining, on the basis of this research, the metrological characteristics of reference materials. Ceramic cylinders based on aluminum oxide were used as the starting material for reference materials; the method to measure the gas permeability coefficient is based on the method of stationary filtration. Measurements of the gas permeability coefficient were carried out on samples with different gas permeability using nitrogen and helium gases. Based on the results of these measurements, for each sample, the gas permeability coefficients were calculated at the given reverse pore pressure and the absolute gas permeability coefficient. As a result of the study, a set of reference materials of gas permeability of rocks (imitators) GSO 11546–2020 /GSO 11550–2020 was approved, the range of certified values is (0.1 10^–3 – 5) μm² , and the expanded uncertainty of certified values Uo (k = 2, P = 0.95), is 3 %. The authors believe that the GSO 11546–2020 / GSO 11550–2020 dataset will ensure metrological traceability and reliability of gas permeability coefficient measurements. As a result, it will bring practical relevance to a petrophysical research laboratory.

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