准噶尔盆地石炭-二叠系方解石脉的碳、氧、锶同位素组成与含油气流体运移

在准噶尔盆地当前油气勘探的重点目标区西北缘和腹部地区，油气主要源于深部石炭系—二叠系。通过对其中的典型水岩反应产物，即裂隙方解石脉进行碳、氧、锶同位素组成分析，尝试讨论了油源流体运移的基本特征。实验结果表明，25件方解石脉样品的δ13CPDB位于－21.5‰~ 5.2‰之间，δ18OPDB(δ18OSMOW)在－8.1‰～－22.3‰(22.6‰~ 6.9‰)之间；20个87Sr/86Sr比值分布在0.703 896～0.706 423之间。据此，结合样品地质产状和区域地质背景，提出本区含油气流体在运移过程中伴随着深部热流体的影响，它们在流经石炭—二叠系时，对火山岩层的溶蚀使得流体岩石相互作用产物，即方解石脉的同位素组成反映出火山岩地层的地球化学标记。该认识表明，在今后的区域储层成岩演化和油气运移研究工作中，应充分考虑这类深部热流体作用的影响。

Carbon, Oxygen and Strontium Isotope Composition of Calcite Veins in the Carboniferous to Permian Source Sequences of the Junggar Basin: Implications on Petroleum Fluid Migration

The presently explored oil and gas in the central and northwestern Junggar Basin are mainly derived from Carboniferous Permian sequences. In this paper, we try to understand the basic features of petroleum fluid based on analyses on carbon, oxygen and strontium isotope composition of typical calcite veins hosted in source sequences. δ13CPDB  of 25 typical calcites ranges from －21.5‰ ~ 5.2‰, and δ18OPDB(δ18OSMOW) locates between －8.1‰ and -22.3‰(22.6‰ ~ 6.9‰). On the other hand, 20 87Sr/86Sr data (0.703 896~0.706 423) are all below the average value of modern seawater (0.709 073). Combined these isotope data and their geologic background, it is suggested that the petroleum fluid in the basin is a mixture of deep sourced hot fluid and oil gas water. It carried volcanic characters by dissolution on the volcano and clastic rocks during hydrocarbon generation and migration. This result indicates that the effect of deep sourced hot fluid must be given enough consideration in the future study of reservoir diagenesis and petroleum migration.