长岭断陷南部地区断陷层油气成藏机制及勘探潜力

Reservoir-forming mechanism and its exploration potential of Songliao Basin in the southern area of Changling Depression

利用天然气组成、轻烃指纹、碳同位素和生物标志化合物以及储层流体包裹体等地球化学特征,结合地质条件以及生烃史-热史模拟研究长岭断陷南部的龙凤山地区油气成因及成藏过程,揭示其油气成藏机制。结果表明:龙凤山地区断陷层天然气属于腐殖型和腐泥型的混合气,且为裂解气和干酪根热降解气组成的混合气,油气源主要为本地的沙河子组烃源岩,原油成熟度低于天然气,为同一油源不同热演化阶段的产物,属于次生凝析气藏,成藏表现为"近源多向供烃,复合输导,早期干酪根热降解成气与晚期原油裂解成气"的多期成藏模式;长岭南部地区发育优质烃源岩、营城组末期形成的反转构造提供了圈闭条件,具备较好油气输导条件、存在多期油气充注,油气勘探潜力大。

The hydrocarbon genesis and reservoir-forming of Longfengshan in the southern Changling Depression was investigated using the geochemical characteristics of natural gas composition, light hydrocarbon fingerprint, carbon isotopes and biomarker, as well as the reservoir fluid inclusion. Also the geological condition and hydrocarbon generation-thermal histories were combined to study the reservoir-forming mechanism. The results show that the genesis of gas in Longfengshan sub-sag is a gas mixture composed of humic and sapropelic gas which consists of oil cracked gas and kerogen thermal degradation gas. It is also found that the natural gas and condensate of reservoir is mainly K1 sh Formation source rock, in which the maturity of oil is lower than that of natural gas. This is the product of different thermal evolution stages of the same oil source, which belongs to the secondary condensate reservoir. The reservoir-forming exhibits the multi-stage reservoir model of ＂ single source for hydrocarbon, multi-type carrier system and early kerogen catalyzed gas accumulation and late oil cracked gas accumulation＂. The developed excellent source rocks and the formed tectonic inversion in the southern Changling Depression supply trap conditions, which present good fluid transporting conditions and multi-period hydrocarbon accumulation showing great potential for oil and gas exploration.