复杂断陷盆地沉积充填演化特征与油气聚集——以塔木察格盆地为例

Sedimentation-filling characteristics and hydrocarbon accumulation in complex rift-subsidence basin: taking Tamtsag Basin as an example

塔木察格盆地是一个经历了多期构造演化形成的复杂断陷含油盆地,为了深入认识该盆地的油气聚集规律,通过对其地构造演化与沉积体系类型响应关系、同沉积断裂带及构造转换带对砂体的控制作用进行分析,明确了油藏类型及其分布规律。研究表明:塔木察格盆地经历了初始裂陷期"窄盆浅水"—强烈裂陷期"窄盆深水"—坳陷期"广盆浅水"的盆地演化过程,分别沉积充填了扇三角洲￣滨浅湖、扇三角洲￣水下扇￣深湖/半深湖、三角洲￣滨浅湖沉积体系;识别出5种控制沉积砂体类型及分布的同沉积断裂坡折带类型,构建了断裂坡折带、构造转换带控砂的砂分散体系模式;沉积充填体系类型的差异性及砂分散体系样式造成不同的油气聚集特征,形成了多层位构造油藏、岩性油藏的复式成藏组合特征。

Tamtsag Basin is a complex oil-bearing faulted basin which formed through multiple tectonic evolutions.In order to deeply recognize the law of hydrocarbon accumulation,analyzing the relationship between tectonic evolution and sedimentary system types and the control effect of synsedimentary faults and tectonic transfer zones on sand body,the types and distribution of reservoirs were defined.Researches indicate： Tamtsag Basin experienced evolution process from the initial rifting stage with narrow basin shallow water to the strongly chasmic stage with narrow basin deep water,and then to the depression stage with wide basin shallow water,and the sedimentary fillings separately are the fan delta-shore-shallow lake,the fan delta-submarine fan-deep lake,semi-deep lake,deltashore-shallow lake; five types of syndepositional fault break zone that control the sedimentary sand body types and distribution were identified; sand distributed system model that fault slope break belts and structural transposition zone controlled sand was constructed; the difference of sedimentary filling system type and sand distributed systems patterns caused different hydrocarbon accumulation characteristics,which formed multi-layer structural reservoir and lithologic reservoir duplex assemblage characteristics.