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鄂尔多斯盆地构造热演化对富氦天然气富集的控制作用初探

Preliminary Study On the Controlling Effect of Tectono-Thermal Evolution on Helium-Rich Natural Gas Enrichment in Ordos Basin

  • 摘要: 鄂尔多斯盆地众多气田中仅东胜气田等个别气田具备氦气资源前景,说明天然气与氦气的富集过程存在一定差异,而温度对这两种气体富集均十分重要。笔者从盆地构造热演化的角度探索天然气成藏与氦气富集之间的关系。通过统计鄂尔多斯盆地基底的氦源矿物及其氦封闭温度,结合盆地构造热演化史,分析烃源岩、氦源矿物分布及天然气生成和氦气释放的时空特征,讨论天然气与氦气的富集过程。结果表明鄂尔多斯盆地内气源岩以上古生界烃源岩为主,分布集中且埋藏较浅,氦源矿物以锆石、独居石和磷灰石为主,分布分散且埋藏较深,烃源岩生气与主要氦源矿物释放氦气的温度、时间重合度较高,二者的富集过程具有时空耦合关系。此外,由于天然气生成的量大且集中,氦气释放的量小而分散,在距离烃源岩沉降中心较近的原生气藏,氦气难以富集,而距离烃源岩沉降中心较远,距离氦源基底较近的次生气藏往往有利于氦气富集成藏。本次研究将构造热演化与天然气富集成藏和氦气释放结合开展研究,开拓新思路,对完善氦气资源调查评价体系具有指示意义。

     

    Abstract: Among the numerous gas fields in the Ordos Basin, only a few gas fields such as Dongsheng Gas Field have the potential for helium gas resources, indicating that there are certain differences in the enrichment process of natural gas and helium, and temperature is very important for the enrichment of both gases. This article explores the relationship between natural gas accumulation and helium enrichment from the perspective of basin tectonic thermal evolution. By analyzing the helium source minerals and their helium sealing temperatures in the basement of the Ordos Basin, combined with the tectonic and thermal evolution history of the basin, this study analyzes the distribution of hydrocarbon source rocks and helium source minerals, as well as the spatiotemporal characteristics of natural gas generation and helium release, and discusses the enrichment process of natural gas and helium. The results show that the upper Paleozoic hydrocarbon source rocks in the Ordos Basin are mainly distributed and shallowly buried, and the helium source minerals are mainly zircon, monazite and apatite, which are dispersed and deeply buried. The temperature and time coincidence of the gas gas in the source rocks and the helium released by the main helium source minerals are high, and the enrichment process of the two has a spatio-temporal coupling relationship. In addition, due to the large and concentrated amount of natural gas generated and small and dispersed amount of helium released, it is difficult to enrich helium in the primary gas reservoir near the settlement center of the source rock, while the secondary gas reservoir far from the settlement center of the source rock and near the base of the helium source is often conducive to the rich and integrated accumulation of helium gas. In this study, structural thermal evolution is combined with natural gas rich accumulation and helium release, which opens up new ideas and has certain significance for improving the helium resource investigation and evaluation system.

     

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