- 學位論文
台灣海域原油的地球化學特徵研究
Geochemical characterization of crude oils from Offshore Taiwan
摘要
台灣第三紀盆地至今主要的油氣發現為天然氣及伴生的凝結油，另外也鑽獲少數的原油，包括台西盆地B地塊上第三系及台西盆地D地塊及澎湖盆地下第三系的原油。原油的發現在台灣較為罕見，在地球化學及石油探勘上具有重要的意義。 本研究選取5個代表性油樣包括4個原油及1個凝結油，進行地球化學研究，包括化學族組份、碳氫化合物組成、生物指標分佈的地化特性鑑定，並探討其在石油探勘上的意義。 研究結果顯示台灣海域台西盆地D地塊及澎湖盆地下第三系同張裂期地層所鑽獲的高蠟質原油具有類似的地化特性，油樣成熟度不高，飽和烴含量高，均含有4-甲基甾烷生物指標，屬於湖相生油岩的產物。此等湖相油樣證實台西盆地及澎湖盆地下第三系同張裂期有湖相石油系統的存在，此湖相生油岩地化特性可對比到珠江口盆地的始新世文昌組生油岩，品質良好，具產油潛能。 台西盆地上第三系後分離期地層的油樣明顯與台西盆地D地塊及澎湖盆地下第三系的湖相原油不同，含有大量高等植物來源的生物指標，產自陸相有機質，主要源自早中新世含煤地層的陸生植物有機質生油岩，台西盆地B地塊E構造木山層油樣研判為初成熟煤成油，北寮層油樣為初成熟的煤成油與成熟的陸相凝結油混合，台西盆地B地塊氣田石底層的天然氣所伴生的凝結油帶有煤樣特徵。
並列摘要
In addition to commercial amount of natural gas with condensates, crude oils have been discovered in the syn-rift Paleogene formation of the Taihsi Basin and Penghu Basin and in the Neogne formation of the Taihsi Basin, respectively. The geochemical characterization of these crude oils may indicate their source organic matter and maturation level, and therefore are meaningful from the viewpoint of petroleum exploration. Five oil samples, i.e., four crude oils and one condensate, were studied for their geochemical characteristics based on the chemical group composition, hydrocarbons composition revealed from gas chromatography, and the biomarker distributions from the gas chromatography-mass spectrometry. The results show the oils from the syn-rift Paleogene formation of the Taihsi Basin and Penghu Basin share similar geochemical characteristics. They are high waxy and comprised of high content of saturated hydrocarbons with biological markers derived from phytoplankton. The occurrence of 4-methyl steranes implies these oils generated from source rocks of lacustrine environment with low maturity. The oil samples of the post-rift Neogene formation of the Taihsi Basin shows geochemical characters significantly different from those of the syn-rift Paleogene formation of the Taihsi and Penghu Basins. The crude oil sample from the early Miocene Mushan Formation of the E structure, Taishi Basin, was distinguished as a low-mature oil generated from coals. The crude oil sample from the early Miocene Peiliao Formation is the mixture of the coal derived oil and mature oil from terrestrial source rocks. The condensate sample of the Shiti Formation from the gas field of the B Block, Taishi Basin is of low maturity and contains a lot of terrigenous biomarkers. The existence of the lacustrine oils confirms the lacustrine petroleum system of the syn-rift sequences in the Taishi and Penghu basins. This petroleum system differs from the post-rift coal-bearing petroleum system of the Neogene formation.