琼东南盆地天然气成因类型及其烃源探讨

Origin mechanism and source rock for natural gas in Qiongdongnan Basin,South China Sea

综合天然气组分、碳同位素组成、轻烃特征、生标化合物分布特征和相关地质资料,对琼东南盆地的天然气成因类型及其烃源进行了分析,其结论认为:盆地东部非烃气含量高,多为CO2和N2,烃气含量不等,多为湿气;盆地西部烃气含量高,多数为干气。盆地中的天然气为混合成因有机成因气,油气主要来源于渐新统的煤系烃源岩和滨海沼泽相烃源岩,始新统中深湖相源岩对盆地晚期生成高成熟—过成熟的原油裂解气有一定的贡献。

Origin mechanism and source rock of natural gas in the Qiongdongnan Basin have been studied according to natural gas composition,stable carbon isotope ratio,light hydrocarbon feature,biomarker and other related geological data.In the east of the basin,non-hydrocarbon gases（mainly CO2 and N2） are in high content and hydrocarbon gas（usually wet ones） are in low content.Gases from the west of the basin are usually dry gases rich in hydrocarbon.Gases in the basin are organic origin,and mainly generated from coal bed source rocks and coastal swamp source rocks of Oligocene.The deep lacustrine source rocks of Eocene also contributed to generate high-mature and over-mature oil-cracking gases.