Gas source of Zhujiadun gas field, Yancheng basin and its discovery significance .

Zhujiadun gas field was discovered recently in Jiangsu. The oil gas produced fr om Tertiary sandstone is divided into three fractions: natural gas, light hydroc arbon and condensate. Gas and light hydrocarbon have humic and over mature feat ure, and condensate has sapropelic and low maturity feature geochemically. It is considered that the gas came from the underlying Palaeozoic source rocks, and condensate came from sapropelic kerogen in Upper Cretaceous source rocks. In th e subsidence period of the Cenozoic basin, the hydrocarbons generated secondaril y by Palaeozoic source rocks migrated upward and passed through fault to Tertia ry reservoir. The discovery of this gas field and special forming mechanism of t he gas pool widely opened the mind of the explorers.