莺山—庙台子地区天然气地球化学特征及成因类型

Geochemical characteristics and genetic types of natural gas in Yingshan-Miaotaizi area

松辽盆地北部莺山—庙台子地区主要发育两套气源岩,深层气源岩沙河子组以腐殖型有机质为主,已达过成熟阶段,中浅层气源岩青山口组以腐泥型有机质为主,目前为未熟—低熟阶段。该地区在中浅层扶、杨油层发现了三站、四站和五站等气田,深层见天然气显示。天然气地球化学特征研究表明,该地区深层天然气以煤型气为主;扶、杨油层天然气以煤型气和油型气的混合气为主,同时混有原油伴生气和生物成因气;萨尔图和葡萄花油层天然气以生物气为主。此外,还根据甲烷碳同位素值计算出扶、杨油层天然气混合比例,表明扶、杨油层混合气中有39%～81%是来自深层的煤型气。研究结果将对该区进一步的天然气勘探有所帮助。

Yingshan- Miaotaizi area developed mainly two sets of gas source rocks in North Songliao Basin. Humic organic matter is mainly in deep gas source rock of Shahezi Formation, has reached the over- matured stage. Sapropel organic matter is mainly in middle- shallow gas source rock of Qingshankou Formation, at present has reached the immature to low- matured stage. Fuyang oil layer in this area have found gas fields of Sanzhan,Sizhan,Wuzhan etc;deep layer can only see natural gas shows. Based on study of gas geochemical characteristics,deep natural gas in this area is mainly coal- type gas; Fuyang oil layer natural gas is mainly mixed gas of coal- type and oil- type,at the same time there exist biogas and associated gas;Shaertu and Putaohua oil layer natural gas is mainly biogas.This paper calculates mixed gas ratio of Fuyang oil layer by carbon isotope value of methane.The result shows 39～81 percentage of the gas is from the coal- type gas of deep layer.The result is helpful for exploration of natural gas in the next stage.