高原咸化湖盆岩性油气藏富集规律——以柴达木盆地西南区为例  

Enrichment Regularity of Lithologic Reservoirs in Plateau Saline Lacustrine Basin:Taking the Southwestern Qaidam Basin for Example

作　　者：施辉[1] 刘震[1] 连良达[1] 毛亚昆[1] 张勤学 杨乾政 吴瑾 

机构地区：[1]中国石油大学(北京)地球科学学院,北京102249 [2]中国石油青海油田分公司,甘肃敦煌736202

出　　处：《天然气地球科学》2013年第4期701-711,共11页Natural Gas Geoscience

基　　金：国家科技重大专项(编号:2011ZX05002)资助

摘　　要：柴达木盆地自新生代以来长期处于青藏高原隆升背景之下,持续分阶段的隆升导致盆地的古海拔变高、湖盆封闭、气候干寒和盐源充足,形成典型的高原咸化湖盆,以"深水成盐"模式为主,湖内"双扩散对流"在斜坡底部能量突变带附近(如断裂下盘)能够快速堆积大量与盐类共生的烃源岩,该类烃源岩有机碳含量虽低,有机质类型却好,具有较高的烃类转化率和保存条件,能够成为优质烃源岩。高原咸水环境有利于发育丰富的水下分流河道、河口坝和滩坝砂体,常分布于坡折带以下;该类型湖盆具有"自我封闭"的地层流体,储层胶结作用又普遍发育,极易形成物性尖灭成因的岩性圈闭,岩性油气藏形成的关键取决于断裂—砂体的油气输导能力。高原咸化湖盆具有典型的"坡折带控砂"和"断裂控藏"的地质规律,岩性油气藏主要富集于坡折带以下,输导断裂发育的区带。The altitude in Qaidam Basin has getting higher since Cenozoic because the basin has been in the structure setting of the Tibetan Plateau continuous and periodical uplifting,which makes the basin have a close, dry and cold environment and abundant salt source. This typical plateau saline lacustrine basin gener-ally precipitates salts in relatively deep water. The source rocks developed with the salts in the zones,which usually have hydrodynamic break, such as footwall of large syndepositional fault, due to the double-diffu-sive convection. Although the TOC of source rocks in this type basin is widely low, excellent kerogen types, high hydrocarbon conversion rate and good preservation conditions still can make them as high-quali- ty source rocks. Plateau saline lake has a favorable environment to develop sandbodies of underwater dis- tributary channel, estuary bar and beach bar, which usually distribute below the slope break belts. It is easy for it to develop lithologic traps because the reclusive fluid system and strong cementation. So the key point of hydrocarbon accumulation is the carrying capacity of fracture-sand conducting system. It is obvious that slope break belts controlling the sandbodies and hydrocarbon accumulation along the fractures in plateau saline lake basin. In summary, the favorable areas for lithologic reservoir are below the slope break belts with rich conducting fractures.

关 键 词：高原咸化湖盆 岩性油气藏 坡折带 成藏模式 柴达木盆地西南区 

分 类 号：TE122.1[石油与天然气工程—油气勘探]