廊固凹陷古近系隐蔽油气藏形成条件及成藏规律

Hydrocarbon generation conditions and rules of the Palaeogene subtle reservoirs in Langgu sag

隐蔽油气藏是廊固凹陷重要的勘探方向。该区古近系隐蔽油气藏的分布范围广,纵向上含油层系多,主要发育岩性尖灭、岩性透镜体等岩性油气藏,以及构造岩性、地层岩性复合型油气藏。该文立于层序地层学的成果分析了全区隐蔽油气藏的形成条件,并按构造带分析了主要的成藏规律:陡坡带是形成上倾尖灭岩性油藏的的有利部位,并发育构造岩性复合型油气藏;洼槽带的生储条件较好,是岩性透镜体油气藏发育的最有利部位;缓坡带受断层控制,主要形成断块-岩性型油藏,在构造主体和沿主要油源断层纵向形成复式聚集带。

Subtle reservoirs are the highlights for the exploration work in Langgu sag. The Palaeogene subtle reservoir distributes in large scale within this region, and contains many oil-bearing layers laterally; the reservoir types are mainly lithologic hydrocarbon reservoirs such as lithologic pinchout hydrocarbon reservoirs and lithologic lenticular hydrocarbon reservoirs and complex hydrocarbon reservoirs such as structural lithologic reservoirs and strata lithologic reservoirs. On the basis of sequence stratigraphic achievements, it is studied in this article that the generation conditions of subtle hydrocarbon reservoirs within the whole area and the dominate generation rules according to structure belts. It is pointed out that the slope break is a preferable position for the formation of updip pinchout hydrocarbon reservoir, and develops structural lithologic complex reservoir. Troughs are ideal positions for the formation of lithologic lenticular reservoirs with good oil bearing and accumulating abilities. The gentle slopes controlled by faults mainly contributed to the formation of fault-lithologic reservoir, which forms complicated accumulation zone in the main part of structure or laterally along the main oil source faults.