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莺歌海盆地是一个新生代形成的富含天然气的沉积盆地,其上第三系及第四系下部沉积岩系中发育有大面积连片成带的泥拱背斜构造。上第三系莺-黄组是浅埋的最主要天然气储集层,所产气体普遍含有CO_2,有一部分气井产高浓度的CO_2。高浓度CO_2天然气主要分布在中央泥拱构造带。分析了莺-黄组所产天然气的地球化学特征,并考虑到南中国海地区在新生代分别经历了4期明显的火山作用、热作用和裂谷作用,莺歌海周边地区广泛发育有中酸性火山岩系,盆地中央上第三系和第四系下部发育有大面积的高温高压泥拱,盆地第三系海相沉积岩系中普遍含有碳酸盐矿物,莺-黄组中下部及梅山组中钙质含量>10％,中央泥拱带具有高地温(>4℃/100)的地质地球物理特征,认为莺歌海盆地的莺-黄组中CO_2是中中新世和第四纪初期由盆地基底花岗岩系热脱气作用和2000～5000m及其以下第三系沉积岩系中的碳酸盐矿物热分解作用或低温水解作用联合贡献的,CO_2的贡献量分别为15％～100％和0～85％。
Yinggehai Basin is a Cenozoic sedimentary basin rich in natural gas. In the Upper Triassic and Quaternary sedimentary rock series, there is a large-scale contiguous mud-claw anticline structure. On the Tertiary Ying-Huang Formation, the most important natural gas reservoir of shallow burial, the produced gas generally contains CO 2, and some gas wells produce high concentration of CO 2. High concentrations of CO_2 natural gas are mainly distributed in the central mud arch zone. The geochemical characteristics of natural gas produced in Ying-Huang Formation are analyzed. Considering that the South China Sea region experienced four obvious volcanism, thermal and rifting in the Cenozoic, respectively, there are a large number of areas around Yinggehai Acidic volcanic rocks, the Central Tertiary and Quaternary Lower Cenozoic developed a large area of high temperature and pressure mud arches, marine sedimentary rocks in the Tertiary generally contain carbonate minerals, Ying - yellow middle and lower Meishan group calcium It is thought that the CO_2 in the Ying-Huang Formation in the Yinggehai Basin is dominated by the basement granite in the basin during the early Miocene and the early Quaternary. The geological and geophysical characteristics of the central mud arch with high geotemperature (> 4 ℃ / 100) And the contribution of CO 2 contributed 15% ~ 100% and 0 ~ 85% respectively to the combined effect of thermal degassing and thermal decomposition or low temperature hydrolysis of carbonate minerals in the Tertiary sedimentary series below 2000 ~ 5000 m. .