Deuterium/hydrogen ratio analysis and characteristics of hydrogen in natural gases

Abstract

The energy and material carried by deep fluids (C, H, and catalytic substances) can facilitate the hydrocarbon generation by activation and hydrogenation in high-mature hydrocarbon sources. However, As H2 in natural gas is generally at trace level, the isotopic measurement is so difficult that less δD‰ of H2 were reported to trace the inorganic hydrogen source. We developed a hydrogen preconcentration equipment to separate and enrich the trace amount of hydrogen in the natural gases by the molecular sieve trap at different temperatures. The enriched hydrogen was carried into GC-IRMS system by carrier gas to measure the isotope composition. This on-line continuous-flow process eases isotope analytical bottleneck of the minor hydrogen in natural gases. A series of manual samples were measured, in which the H2 content and isotope ratio could be precisely detected. The results show that the method has a good repeatability and linearity. Using this method, δD‰ of H2 in gas samples from Ordos Basin and Jiyang Depression were measured, Although those samles are all from region where the deep fluid is active, Concentration of H2 are below 2.0×10−4 (V/V) and their δD value is −712‰∼−628‰, showing larger isotopic fractionation of hydrogen under deep fluids and organic-inorganic interaction.