渤中坳陷超压-构造活动联控型流体流动与油气快速成藏

渤中坳陷是东营组沉积期及其之后渤海湾盆地沉降-沉积速率最高的地区, 亦是晚期断裂活动最强烈的地区.较高的沉降-沉积速率产生了重要的成藏物质效应: (1) 持续的较快速沉降-沉积使东营组发育较深湖-深湖相泥岩并成熟, 从而使渤中坳陷发育沙河街组和东营组2套有效源岩; (2) 较高的沉降-沉积速率引起的压实不均衡及伴生的源岩快速生烃引起较强的超压, 超压对有机质热演化的抑制作用使沙河街组源岩生、排烃滞后, 从而使沙河街组和东营组在晚期同时保持在较有利的生、排油阶段, 这是渤中坳陷油气资源丰富和油气晚期快速成藏的物质基础.较强的超压和强烈的断裂活动决定了超压-构造活动联控型流体流动, 进而决定了油气幕式快速成藏过程和油气分布: 油气主要富集于新近系, 新构造运动控制油气分布 

Overpressure-Tectonic Activity Controlled Fluid Flow and Rapid Petroleum Accumulation in Bozhong Depression, Bohai Bay Basin

Since the beginning of the deposition of Dongying Formation, the Bozhong depression has had the highest subsidence-sedimentation rates and the strongest late-stage (since 5.1 Ma) fault activity in the Bohai Bay basin. High subsidence-sedimentation rates have had very important "material" effects on petroleum accumulation. On one hand, both Dongying and Shahejie formations comprise effective source rocks in the Bozhong depression because of much thick overlying strata, whereas only Shahejie Formation is taken as effective source rocks in almost all other depressions in Bohai Bay basin. On the other hand, strong overpressure caused by compaction disequilibrium due to rapid subsidence and sedimentation retarded organic matter maturation especially hydrocarbon thermal destruction and delayed petroleum expulsion, which made both Shahejie and Dongying formations remain in a favorable conditions for petroleum generation and expulsion during late stage (since (5.1 Ma)). The "material effect" is a key for the rapid petroleum accumulation around Bozhong depression. The combination of strong overpressure and strong faulting during late stage controlled fluid flow as a result of episodic petroleum accumulation. Hence, such a process controls the distribution of petroleum occurring in Neogene strata.