青藏高原羌塘盆地油源及运移过程

OIL SOURCE AND HYDROCARBON MIGRATION PROCESS IN QIANGTANG BASIN,QINGHAI-TIBET PLATEAU

羌塘盆地隆鄂尼西J2b、昂达尔错J3s、西长梁J3s及安多114道班J3s油苗和比洛错J2x富烃页岩及安多114道班J3s深灰色灰岩均具有重排甾烷含量相对较高、孕甾烷含量低、三环萜烷和γ—蜡烷含量较低、Pr/Ph较高、碳同位素相对较重的特征。隆鄂尼西J2b及昂达尔错J3s油苗主要来自本区J2x潟湖相富烃源岩;安多114道班J3s及西长梁J3s油苗主要来自本区J3s海相盆地内台凹相深灰色灰岩及富烃页岩。盆地中部含油白云岩及安多114道班J3s灰质角砾岩中存在“轻质活油”和“固体沥青”。“固体沥青”是第一次油气运移聚集成古油藏的产物;发荧光的“轻质活油”则是再次埋深或构造运动所导致的第二次或第三次油气运移聚集成藏的产物,它们经历过2次(或2次以上)油气生成和运移的过程。

The oil seepages from the formations of J2b in West Longeni, J3s in Angdaercuo, J3s in West Changliang and J3s in the area of No. 114 Anduo road maintenance squad as well as the J2x hydrocarbonrich shale in Biluocuo and the J3s dark-gray limestone in the area of No. 114 road maintenance squad are characterized by high rearrangement sterane content, low pregnane, triclene and gammacerane contents, high ratio of Pr/Ph as well as heavy carbon-isotope. The oil seepages in the formations of J2b in West Longeni and J3s in Angdaercuo originate from the J2x lagoon-phase hydrocarbon rich source rock in their corresponding areas. The oil seepages in the formations of J3s in the areas of No. 114 Anduo road maintenance squad and West Changliang originate from the J3s platform facies dark-gray limestone and hydrocarbon-rich shale. There are ＂light active oil＂ and ＂solid bitumen＂ in the oil-bearlng dolomite in center of the basin and in the Jas lime-rubble rock in No. 114 Anduo road maintenance squad area. The solid bitumen is product of the first hydrocarbon migration and accumulation. The fluorescent light active oil is product of the second or third hydrocarbon migration and accumulation causing by reburial or tectogenesis. They have undergone two or more hydrocarbon generation and migration processes.