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珠江口盆地珠三坳陷发育早期为断陷湖泊发育期(古新世—早渐新世).勘探证实该时期是坳陷内主要烃源岩形成期.珠三坳陷古湖泊的演化经历了三个阶段:早期山间湖泊阶段、中期湖泊鼎盛阶段和晚期湖泊萎缩阶段,总体来说三个阶段的湖水性质为低矿化度、低CaCO_3含量的淡水,但生物发育以及沉积物供给等条件有所不同,湖泊鼎盛阶段浮游藻类大量发育,水体的垂直分层使有机质得到了保存,形成了本坳陷最好的生油岩;湖泊萎缩阶段大量陆源碎屑进入,广泛发育湖沼相沉积,形成了以煤系地层为主的气源岩.古湖泊不同阶段形成的两套烃源岩,决定了坳陷内存在两套油气体系.
The early development of the Zhujiang Depression in the Pearl River Mouth Basin is characterized by lacustrine rift lacustrine development (Paleocene-Oligocene) .Performance exploration confirmed that this period was the main source rock formation in the depression. The evolution of the ancient lakes in the Zhu 3 sag Three stages: the early mountain lakes, the mid-lakes heyday and the late lakes shrinking. Generally speaking, the three stages of the lake are low salinity and low CaCO_3 freshwater, but biological development and sediment supply The conditions are different. In the heyday of the lake, a large number of phytoplankton are developed. The vertical stratification of the water body can preserve the organic matter and form the best source rock in the depression. A large number of terrigenous debris enter the lake during the shrinkage stage and the lacustrine facies sedimentation , Forming gas source rocks mainly dominated by coal measures.The two sets of source rocks formed at different stages of the ancient lakes determine that there are two sets of oil and gas systems in the depression.