渤海海域秦南凹陷油气地质特征及勘探潜力

Hydrocarbon Geological Characteristics and Exploration Potential of Qinnan Depression in Offshore Area of Bohai Sea

秦南凹陷是渤海海域勘探程度最低的凹陷之一,前期勘探成果不理想,凹陷的生烃能力一直受到质疑。通过对秦南凹陷油气地质特征研究表明:秦南凹陷内小型次洼已具备较大的生排烃能力,凹陷中心的东洼和中洼烃源岩分布范围更广、体积更大、埋藏更深,应具有更大的生排烃能力;凹陷的结构类型控制油气优势运移方向;稳定分布的东二下段泥岩沉积控制了油气富集层位;长期活动断层的发育位置及程度控制了新近系油气成藏的区域与富集程度;主要发育了自生自储、早生晚储、下生上储近源成藏3种成藏模式。研究认为,石臼坨凸起北侧斜坡区、秦南凸起东侧斜坡区以及秦南Ⅰ、Ⅱ号断裂附近为有利勘探区域,具有较大勘探潜力。

Qinnan depression is one of the depressions in offshore Bohai Bay Basin where exploration maturity is the lowest. The previous exploration effect of the depression was not satisfactory with its hydrocarbon sourcing capacity questioned. Source rock is more extensively distributed and more deeply buried in Dongwa and Zhongwa, the central areas of the depression, with a larger thickness. Therefore, the central part of the depression has a higher capacity for hydrocarbon sourcing and expulsion. The structural type of the depression controlled the direction of advantageous oil and gas migration. The steadily-distributed mudstone deposit of the second member of Dongying Formation controlled the oil and gas abundance level. The development locations and degrees of long-term active faults controlled the areas and abundance degrees of the Neogene hydrocarbon accumulations. There were mainly three accumulation patterns in the region - the self- sourcing and self-storing pattern, the early-sourcing and late -storing pattern and the lower-sourcing and upper-storing near-source pattern. The study indicates that the slope zone north of Shijiutuo uplift, the slope zone east of Qinnan uplift and the areas near Qinnan Ⅰ fault and Qinnan Ⅱ fault are the favorable exploration zones with a great potential for exploration.