大型油气系统形成的盆地动力学背景

找寻大油气田的急迫任务带动了当今新一轮战略性、区域性的基础地质和石油地质研究.在盆地中识别富生烃凹陷及其所控制的油气系统具有关键意义.没有富生烃凹陷就没有大油气田赖以形成的首要基础.富生烃凹陷及大型油气系统的形成又有其特有的盆地动力学背景, 认识后者对前者的控制关系可提供战略性预测.渤海湾盆地作为中国东部陆上及海域伸展类盆地最重要也最典型的代表, 其数十年勘探和研究历程揭示了富生烃凹陷、大型油气系统和盆地动力学过程的内在联系.岩石圈伸展和裂陷的背景下, 盆地内隆坳分异的构造格架、快速沉降、高地温和异常高压系统提供了富生烃凹陷和大型油气系统形成的构造背景, 与古近系中晚期有利的古气候、古环境条件匹配形成了最有利生烃的超富养湖盆类型.根据多个富生烃凹陷的典型研究提出了大型油气系统形成的模式, 进一步分析了富生烃凹陷形成背景的多样性.值得指出的是, 目前所知西北地区大型叠合盆地中最重要的富生油凹陷, 如准噶尔盆地的二叠纪中央凹陷、塔里木盆地的满加尔凹陷可能都形成于伸展和裂陷背景下, 中新生代则以挤压、挠曲占优势.提出用当代盆地动力学和油气系统的思路与方法重新认识含油气盆地及其油气系统演化的动力过程, 进行新一轮基础性、区域性研究, 为发现新领域、找寻大油气田提供地质理论基础. 

Basin Geodynamics Background of Formation of Huge Petroleum Systems

A new stage of the basic and strategic research of petroleum geology has already started in recent years for discovering significant hydrocarbon accumulation in China. Geologists are facing great challenge and opportunities in this decade and the near future. A critical research field is to recognize the hydrocarbon-rich depressions and their relative petroleum systems in petroliferous basins. Based upon case studies of the Chinese basins, all hydrocarbon-rich depressions have their special basin dynamics background. The Bohaiwan basin is a most important representative one in eastern China. During rifting phase structure framework comprised by a number of half-grabens and associated horsts, rapid subsidence, high geothermal and (overpressured) chambers within source rocks offered excellent conditions for the formation of huge petroleum systems under the lithospheric extension setting. Optimum paleo-climite and lake types in Eocene time may be favorable for the formation of high quality oil source rocks. Two concept models on petroleum system in the Bohaiwan rift basin have been proposed based upon the integrated research of basin evolution and case studies of hydrocarbon accumulation in typical depressions. It is worthy to note that most of important hydrocarbon-generating depressions in large scale superpositional basins of northwest China are also formed in extensional setting, such as the Permian central depression of the junggar basin, the Manjiaer depression of the Tarim basin. The research results elaborate the dynamic processes of hydrocarbon-generating depressions and provide an important theoretical base for the exploration of large oil and gas fields.