渤海湾盆地重点凹陷断裂活动-超压协同演化及其控制的油气运移动力学机制

Dynamics of petroleum accumulation is the central issue and an important area for the further development of petroleum geology. It focuses on the development and evolution of basin energy field and its control on the kinetic and dynamic processes of petroleum generation, migration in sedimentary basins. The major types of basin energy field include three ones: overpressure-dominated, tectonic activities-overpressure controlled and hydrostatic pressure-tectonic activities controlled. In this project, some important depressions of the Bohai Bay Basin (including depressions of Western Liaohe, Central liaodongwan, Bozhong, Huanghekou, Laizhouwan) were selected for the frontier studies, i. e. the fault activities-overpressure co-evolution and the dynamic mechanism of petroleum migration for the basin. The fault activities-overpressure co-evolution will be quantitatively deciphered through distinguishing the spatio-temporal differences of fault activities among the depressions, combined with paleo-pressure reconstruction using fluid inclusion thermodynamic modeling. The regimes of fault activities-overpressure during the major phases of hydrocarbon generation and expulsion in the depressions will be determined and compared for establishing their dynamic mechanisms of petroleum expelling and migration, consequently trying to explain differential effects of fault activities-overpressure co-evolution on the petroleum-expelling efficiency and the hydrocarbon occurrence among the depressions.

油气成藏动力学是石油地质学研究的难点与发展趋势，其核心研究内容是能量场演化及其控制下的生烃动力学和油气运移动力学。含油气盆地能量场环境主要包括超压主导型、构造活动-超压联控型、常压-构造活动型。本项目针对构造活动-超压联控型盆地能量场发育演化及其油气运移动力学机制这一前沿研究领域，以渤海湾盆地重点凹陷(包括辽河西部凹陷、辽中凹陷、渤中凹陷、黄河口凹陷以及莱州湾凹陷)为研究对象，基于重点凹陷断裂活动时空差异分析，采用流体包裹体热动力学模拟技术恢复古压力，揭示重点凹陷断裂活动-超压协同演化及其差异。分析重点凹陷烃源岩主生排烃期断裂活动、超压状况及其差异，阐明重点凹陷烃源岩排烃与油气运移动力学机制及其差异，探索断裂活动-超压协同演化差异对源岩排烃效率与油气分布的影响。

阐明了渤海湾盆地断裂活动与超压发育演化之间的协同关系，即在断裂活动薄弱带泥岩较强欠压实，砂岩(强)超压发育，压力系数接近2.0，断裂活动强烈带，尽管泥岩欠压实，但砂岩近于正常静水压力；基于大民屯凹陷研究，建立了超压主导以及超压-应力主导环境烃源岩排烃动力学模式。基于生热烃模拟实验，建立了渤海湾盆地主力烃源岩生烃模型，液态烃高峰在Ro%为0.9，气态烃高峰为1.2，原油大量裂解成气起点为1.3；为动态成藏分析提供了更准确的生烃史。依据渤海海域近100条主干断层与油气圈闭相关断层活动 (尤其新构造运动) 强度计算及其与油气富集的关系分析表明，断裂活动速率>25m /Ma断层起输导作用，<10m /Ma断层起遮挡作用，建立“主断层输导、次要断层遮挡的黄金搭档”油气输导富集模式；揭示了QHD29-2油气藏断层分段式输导与遮挡油气成藏机制及其地球化学标志；阐释了渤海湾盆地渤中坳陷及其周缘凹陷与凸起带油气主要富集于新近系，其他地区主要富集于古近系的油气分布规律；该模式对于渤海湾盆地断层圈闭有效性判别具有实际参考价值。