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研究天然气中Ｎ２的成因与富集有助于了解含油气盆地烃源岩的热演化阶段和天然气成藏史，有助于了解盆地的油气资源潜力，以便指导油气资源评价和降低勘探风险。地下Ｎ２的潜在来源很多，每种来源对天然气的可能贡献是都不尽相同。天然气中Ｎ２的主要成因有：（１）沉积有机质在过成熟阶段高温裂解产生的Ｎ２；（２）沉积岩中铵粘土矿物变质作用释放了Ｎ２；（３）沉积有机质在成熟阶段经热氨化作用形成的Ｎ２；（４）沉积有机质在未

ORIGIN AND ENRICHMENT OF NITROGEN IN NATURAL GAS

??The research on the origin and enrichment of nitrogen in natural gas is conductive to understanding the thermal evolution level of hydrocarbon source rock,gas reservoir formation history and resource potential in oil-and gas-bearing basin so as to guide oil&gas resource evaluation and to reduce exploration risk.There are various nitrogens underground and each probable contribution to natural gas is different.The major origins of the nitrogens in natural gas include:??the nitrogen produced by the pyrolysis of organic matter in postmature phase with high temperature (??300);??the one released through the metamorphism of clay minerals containing ammonium in sedimentary rocks;??the one formed by the thermal ammoniation of sedimentary organic matter in mature phase;??the one formed by microbial ammoniation of sedimentary organic matter in immature phase;??the one coming from atmospheric air;??the original nitrogen coming from the ultra-deep part of earth crust and the outer mantle;and?? the nitrogen formed by the chemical reduction and microbial reverse nitration of the nitrate in evaporite rocks.The reasons for the enrichment of nitrogen in natural gas may be:??the enriched nitrogen and enriched methane originated in different ways or at different stages in the same way and they were not mixed in the processes of the migration,accumulation and preservation;and ??because of migration the nitrogen content is low in natural gas and the geological-chromatographic differentiation has effectively happened between the nitrogen and methane.