| Based on geochemistry, the paper was mainly about the geochemical characters of crudeoils in Banqiao Sag. Combined with the source rocks research, the oil was categorized intoseveral families by the method of oil-source correlation. All of this is helpful to study the oilgeneration, migration and accumulation.Firstly, the source rocks`geochemical characters were studied involving with the types,abundance and maturity of organic matter. In the studied area, it exist two effective sourceformations, Sha-1formation and Sha-3formation. The study shows that the Sha-1formationwas formed in salt water sedimentary environment and Sha-3formation formed in fresh watersedimentary environment. The organic matter of Sha-1was mainly from phytoplankton andSha-3`s organic matter mainly from higher plants. The study also shows that the source rocksof Sha-3were obviously affected by microbes.Secondly, the crude oils`geochemical characters were analyzed in details involvingbiomarker, aromatic hydrocarbon, physical property, group composition, carbon isotope andlight hydrocarbon. And then the oil was divided into four families, marked with Ⅰ, Ⅱ, Ⅲ andⅣ. The Ⅰ type oil was characterized with the highest saturated hydrocarbon, the heaviestcarbon isotope, a high rate of Pr/Ph, and high abundance of sterane and terpane. The obviouscharacter of Ⅱ type oil was biodegradation. The Ⅲ type oil was with higher saturatedhydrocarbon, the lightest carbon isotope, a low rate of Pr/Ph, and moderate amount of steraneand terpane. And the Ⅳ type oil was of high amount of nonhydrocarbon and asphaltic, lightcarbon isotope, and no4-methyl sterane exist.The study of oil-source correlation shows that the oils in Banqiao Sag were from bothsingle source and multiple sources, and the latter with a higher probability. The study showsthat the Ⅰ type oil is only from Sha-3source rocks, the Ⅱ type is biodegradation oil, the Ⅲtype oil is from multiple sources, and the Ⅳ type oil is only from Sha-3sources rock inTanggu region. |
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