柴达木盆地北缘冷湖地区侏罗系—古近系储层流体包裹体特征与油气运移

Reservoir Fluid Inclusion Feature of Jurassic-Paleogene Age from the Northern Qaidam Basin and Its Implication on Hydrocarbon Migration

柴达木盆地北缘冷湖地区的侏罗系—古近系储层是柴北缘地区的重点勘探对象,通过对采自该区7口典型钻井中的储层岩心样品进行流体包裹体分析,揭示了油气运移的一些基本特征。首先,根据储层含油气包裹体丰度的差异,认为冷湖地区并不存在从五号→四号→三号构造的顺层油气运移指向,油气主要自昆特依凹陷呈放射状向构造带运移。其次,储层油气包裹体类型的差异表明,深部侏罗系储层中曾经接受过一期成熟度较低的石油充注,但规模可能有限;冷湖地区可能并不存在大规模的天然气聚集;原油普遍遭受过水洗降解等次生变化。最后,综合包裹体岩相学和显微测温结果,提出本区侏罗系—古近系储层中目前所发现的油气大多为中新世后形成。这些认识为区域油气深入勘探提供了重要的基础参考信息。

The Jurassic-Paleogene reservoir of the Lenghu area is a key object of petroleum exploration in the northern Qaidam Basin. In this paper, a detailed fluid inclusion study was carried out based on seven typical wells collected from the Lenghu area. This leads to some novel and deeper understanding of hydrocarbon migration in the study area. Firstly, according to oil inclusion abundance, it is suggested that there is not a hydrocarbon migra- tion direction from Structure No. 5, to No. 4 and to No. 3. Hydrocarbons sourced form the Kunteyi sag migrated radiatingly. Secondly, oil inclusion type indicates that some low-maturity hydrocarbons have accumulated in the Jurassic reservoir with not large volumes. Additionally, gas has little possibility to accumulate here and it is com- mon that reservoir oils have been secondarily altered. Lastly, combined inclusion petrography and microthermome- try, it is proposed that the presently explored oil-gas was mostly formed since Miocene.