黄骅坳陷石炭-二叠系凝析油气地球化学特征及来源分析

深层油气勘探是未来油气资源的重要接替领域。渤海湾盆地下伏石炭-二叠系煤系烃源岩自油气勘探取得新突破以来，一直是深层油气领域研究的热点。黄骅坳陷新部署的QG8井奥陶系碳酸盐岩储层和YG1井二叠系砂岩储层获高产凝析油气流，其来源判别问题是深层油气勘探的关键。针对QG8、YG1井凝析油气开展的生物标志化合物、有机碳稳定同位素和原油物性研究表明：两口井的凝析油均为低黏度、低密度的典型轻质原油，具有姥鲛烷优势（Pr/Ph>2.8），QG8井凝析油饱和烃δ¹³C为-29.1‰、芳烃δ¹³C为-26.8‰；天然气δ¹³C₁偏重，介于-39.7‰~-36.4‰之间，干燥系数大于0.8，重烃可达16.2%，为偏干湿气。QG8与YG1井凝析油特征与黄骅坳陷石炭-二叠系煤系烃源岩（饱和烃δ¹³C为-29.26‰~-26.87‰，芳烃δ¹³C为-26.62‰~-24.15‰）及KG4井原油物性（0.757 1~0.840 2 g/cm³）相近，天然气特征则相似于济阳坳陷GBG1井的煤成气（δ¹³C₁为-43‰~-35‰），表明高产的凝析油气来自石炭-二叠系煤系烃源岩。证实渤海湾盆地深层石炭-二叠系煤系具有生烃潜力和油气勘探前景。

Geochemical Characteristics and Source Analysis of Carboniferous-Permian Condensate Oil and Gas in Huanghua Depression

Deep oil and gas exploration is an important replacement area for oil and gas resources in the future. Since the oil and gas exploration of the Lower Carboniferous-Permian coal-series source rocks in Bohai Bay basin has made new breakthroughs, it has become a research hotspot in the deep oil and gas field. The high-yield condensate gas flow has been obtained in the newly deployed Well QG8 and Well YG1 in the Dagang exploration area, and the source identification is the key to deep oil and gas exploration. The analysis result indicates that the condensate from well QG8 and Well YG1 is light oil with low viscosity and density. The condensate has high pristane (Pr/Ph>2.8),and the stable carbon isotope (δ¹³C) of n-alkanes and aromatic hydrocarbons of Well QG8 condensate is -29.1‰ and -26.8‰ respectively. The δ¹³C₁ of natural gas is heavier, ranging from -39.7‰ to -36.4‰ with drying coefficient more than 0.8,and the heavy hydrocarbon content is higher, up to 16.2%,belonging to wet gas prone to dry. It is found that the characteristics of condensate oil and gas of Well QG8 and Well YG1 are similar in stable carbon isotopes in extracts (saturated hydrocarbons δ¹³C=-29.26‰—-26.87‰, aromatic hydrocarbons δ¹³C=-26.62‰—-24.15‰, natural gas δ¹³C₁=-43‰—-35‰,and crude oil physical properties of density is 0.757 1-0.840 2 g/cm³), indicating that the condensate oil and gas come from the Carboniferous-Permian coaly source rocks. It is confirmed that the Carboniferous-Permian coaly source rocks in Bohai Bay basin have hydrocarbon generation potential and oil-gas exploration prospect.