Abstract: Faulted basins are important oil and gas production bases in China. With the progress of hydrocarbon exploration, the proportion of the proved conventional oil and gas resources in the shallow and middle layers (depth<3 500 m)has exceeded 60 % , and hydrocarbon resources in tectonic traps of the uplift area are exhausted after years of exploration. There is an increasing difficulty in exploring large-scale oil and gas reservoirs, and the focus is shifted to the exploration of middle and deep layers. Based on the researches of hydrocarbon generation, sedimentation, reservoirs and source-reservoir matching relationship in the Bohai Sea area, the paper systematically summarizes the petroleum geological conditions for tight oil and gas accumulation, which, in combination with the exploration practice of tight oil and gas, an analysis is conducted on the exploration potential of shale oil. The results show that under the control of fault activity, lake level rise and fall, and source supply intensity, there are four types of tight reservoir sedimentation in the middle and deep Paleogene layers, including near-source fan delta in steep slope zone, saline medium braided river delta, sublacustrine fan in slope and depression zone, and carbonate deposition in arid and uncompensated lake basin. When the burial depth exceeds 3 500 m, the reservoir is gradually densified under compaction, and the tight reservoir mainly exhibits the physical characteristics of low and ultra-low porosity and permeability. Deep burial depth, complex composition, and carbonate cementation are the main reasons for the development of tight reservoirs, and dissolution pores and fractures are the main storage spaces. There is relatively large accommodating space in deep depression areas during the pan-lake period, which is conducive to the formation and preservation of organic-rich shale, boasting of superior source rock conditions. The exploration practice of tight oil and gas in the Paleogene reservoirs has confirmed that the Bohai Sea area has the potential for large-scale exploration of tight lithological oil and gas reservoirs, and superior conditions for the development of shale oil as well as enormous resource potential. These unconventional oil and gas resources can provide an important foundation for sustainable exploration and discovery in Bohai oilfield.

Key words: Bohai Sea area, Paleogene, tight oil and gas, shale oil, exploration potential

摘要： 断陷盆地是中国重要的油气生产基地。随着油气勘探开发的日益深入,中—浅层(深度<3 500 m)常规油气资源探明程度超过60 % ,凸起区构造圈闭勘探殆尽,寻找大规模油气藏的难度增加,勘探重点逐步转向中—深层。通过对渤海海域生烃、沉积、储层及源-储匹配关系等研究,系统梳理了致密油气成藏的石油地质条件,结合致密油气勘探实践分析了页岩油勘探潜力。研究结果表明:受断陷活动、湖平面升降和物源供给强度控制,古近系中—深层发育近源陡坡带扇三角洲、咸水介质辫状河三角洲、斜坡—凹陷区湖底扇、干旱欠补偿湖盆碳酸盐岩沉积4类致密储层沉积类型,当埋深大于3 500 m后,储层受压实作用控制而逐渐致密化,致密储层主要表现为低孔—特低孔、低渗—特低渗的物性特征,埋深大、成分复杂、碳酸盐胶结是储层致密的主要原因,溶蚀孔隙与裂缝是主要的储集空间。深凹区在湖泛期具有相对较大的可容纳空间,有利于富有机质页岩的形成和保存,具备优越的源岩条件,古近系致密油气的勘探实践证实渤海海域具备大型致密岩性油气藏勘探潜力,同时页岩油发育条件优越且资源潜力巨大,这些非常规油气为渤海油田可持续勘探发现提供了重要的资源基础。

关键词: 渤海海域, 古近系, 致密油气, 页岩油, 勘探潜力