川中须家河组致密气运移地球化学示踪
Geochemical tracing of tight gas migration in Xujiahe Formation in central Sichuan Basin
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摘要: 致密气成藏研究近年来备受关注,天然气在致密储集层中能否大规模运移是所关注的焦点之一。从天然气地球化学角度,以川中须家河组典型致密气藏为研究对象,用天然气组分参数对川中须家河组致密气进行地球化学示踪研究,来回答天然气能否在致密储集层中发生大规模运移的问题。川中须家河组气藏平面上大面积断续分布,纵向多个独立气藏互相叠加。研究表明,在横向上,川中须家河组相邻气田之间,相同层系的天然气组分参数有明显差异,天然气没有发生横向运移现象。在纵向上,须家河组内上、下气藏之间天然气地球化学特征具有明显差异,这种差异不符合天然气运移分馏规律,说明天然气也未发生明显的垂向运移。换言之,须家河组致密气是原地或近距离聚集成藏,天然气没有经过大规模运移。Abstract: The research on the accumulation of tight gas has attracted much attention in recent years,and whether nat-ural gas can move in large volumes in a tight reservoir is one of research focuses. In this paper,from the perspective of natural gas geochemistry,the typical tight gas reservoirs in the Xujiahe Formation in central Sichuan are studied to an-swer the question of whether natural gas can be transported in a large scale in tight reservoirs,using the natural gas component parameters. Horizontally,the Xujiahe Formation gas reservoirs are widely distributed intermittently,and ver-tically,multiple gas reservoirs are superimposed. Studies have shown that in the horizontal direction,there are signifi-cant differences in natural gas component parameters,and no horizontal migration of natural gas in the same layer be-tween adjacent gas fields. Vertically,there are significant differences in the geochemical characteristics of natural gas between the upper and lower gas reservoirs in the Xujiahe Formation. This difference does not meet the law of natural gas migration and fractionation,indicating that there has been no significant vertical migration of natural gas. In other words,the tight gas in the Xujiahe Formation is formed in situ or at close range,and has not undergone large-scale mi-gration.