南海北部大陆边缘琼东南盆地有利油气聚集带及勘探方向

琼东南盆地处于欧亚板块、印-澳板块及太平洋板块三大板块交汇区,新生代构造沉积演化及油气地质条件较复杂。盆地基本构造格架具有下断上拗及南北分带、东西分块的特征,造成了盆地凹陷构造展布格局,以及地层、层序系统与沉积体系发育,有效烃源岩类型及其分布,储、盖层发育及其展布特征,油气运移输导特征以及油气成藏主控因素等均存在较大的差异。根据盆地构造演化与沉积充填特征,结合该区油气勘探实践,笔者总结出环崖南凹陷有利油气聚集带、宝岛凹陷北坡有利油气聚集带、2号断裂带有利油气聚集带、南部隆起(低凸起区)有利油气聚集带四大有利油气聚集区,且根据这些有利油气勘探区带油气地质特征,重点对主要烃源岩、储盖组合类型、油气输导条件及油气运聚成藏模式等进行了深入分析探讨,在此基础上阐明了不同油气聚集带的成藏主控因素,指出了有利油气勘探方向,为该区进一步油气勘探部署及油气资源预测评价等提供了参考与借鉴。

THE FAVORABLE PETROLEUM ACCUMULATION BELTS AND EXPLORATION TARGETS IN QIONGDONGNAN BASIN ON THE MARGIN OF NORTHERN SOUTH CHINA SEA

The Qiongdongnan Basin is located in the juncture of the Pacific plate, India-Australia plate and Eurasian plate, and characterized by complex Cenozoic tectonic and sedimentary evolution and petroleum geology. The basic tectonic pattern in "E-W zonation and S-N segmentation" made the depressions of the basin different in the distribution of valid source rocks, petroleum accumulation conditions, stratigraphic and sedimentary system and structural framework. Based on the tectonic evolution and sedimentary filling history, combined with oil and gas exploration practice in the basin, we generalized four favorable petroleum accumulation belts, including the Yanan sag and its surrounding area, the northern area of Baodao sag, the No.2 Fracture tectonic belt, and the southern uplift (low uplift) area. According to the petroleum geological features, this paper analyzed in depth the source rocks, reservoir-cap assemblages, petroleum conduction and migration conditions as well as hydrocarbon accumulation models of each favorable petroleum accumulation belt, and main accumulation controlling factors of each belt were also figured out based on above work. Finally, we proposed the prospecting targets of the basin, so as to provide some clues for the future oil and gas exploration and resources assessment.