阿根廷科罗拉多盆地油气地质特征与勘探潜力

Petroleum Geological Characteristics and Exploration Potential of Colorado Basin, Argentina

阿根廷东部大西洋沿岸的科罗拉多盆地是一个勘探程度较低的被动陆缘盆地,已钻的多口探井具有油气显示。该盆地主要经历了3个演化阶段:前裂谷期、同裂谷期和后裂谷期,其中后裂谷期又可划分为热沉降阶段和被动陆缘阶段。同裂谷期盆地内形成了地堑和半地堑构造,使得中央坳陷沉积地层厚度达到15 km。通过钻井和地震解释资料,结合构造和沉积相分析,认为盆地内存在成熟的油气生成、运移、聚集和保存条件。最有利的成藏组合位于盆地东部同裂谷期Colorado组,以下白垩统湖相页岩为烃源岩、浅海相砂岩为储层,主要为地层圈闭。勘探主要风险在于油气能否从生烃凹陷长距离运移到盆地边缘储层,以及顶部盖层能否起到足够的遮挡作用。

The Colorado basin in the Atlantic coast of eastern Argentina is a less explored passive continental margin basin with a number of exploration wells have been drilled with hydrocarbon displays.The basin has mainly experienced three evolution stages:pre rift period,synrift period and post rift period.The post rift period can be divided into thermal subsidence stage and passive continental margin stage.During the synrift period from Late Jurassic to early Cretaceous,the rift extension formed graben and half graben structures,creating a large amount of accommodation space,and the thickness of sedimentary strata in the central depression reached 15 km.According to drilling and seismic interpretation data,combined with structural and sedimentary facies analysis,it is considered that there are sufficient conditions for oil and gas generation,migration,accumulation and preservation in the basin.The most favorable play is the Colorado formation in the eastern part of the basin.The lower Cretaceous lacustrine shale is the source rock,and the shallow marine sandstone is the reservoir,which is mainly stratigraphic trap.The main risk of exploration lies in whether oil and gas can migrate from hydrocarbon generating depression to the reservoir at the edge of the basin for a long distance,and whether the top cap rock can prevent hydrocarbon from escaping.