Geochemical characterization of crude oils from Offshore Taiwan

• Main Authors: Chi-Hsun Hsieh, 謝奇勳
• Other Authors: Yuen-Chih Ting
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/kb588u

碩士 === 國立臺北科技大學 === 資源工程研究所 === 100 === 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.