盐城朱家墩气田气源及发现意义

盐城凹陷位于苏北盆地盐阜坳陷的东南部，南邻建湖隆起，西北与塘洼－大喇叭凸起相接，东至黄海，由两个呈南东倾的箕状凹陷组成（见图1）。凹陷内中、新生界厚逾5000m，钻井揭示的地层自下而上有：古生界，中生界上白垩统浦口组（K2p）、泰州组（K2t），下第三系阜宁组（E1f)、戴南组（E2d）、三垛组（E2s），上第三系盐城组（Ny）和第四系东台组（Qd)。凹陷由南向北被二级断层分割成3个次级构造单元，即南洋次凹、中央隆起和新洋次凹。朱家墩构造位于南洋次凹深凹带，是盐二、盐三两条北掉断层夹持的断背构造，高点埋深3740m，构造面积24km^2。

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.