| 其他摘要 | The Tertiary source rocks are widespread in the East China Sea and play an important role in the formation of oil and gas in this area according to the exploration and studies. The dissertation chooses the Xihu and Taibei depressions as a case study. The characteristics of organic petrology, coal petrology, petroleum geology, geochemistry of oil and gas have been invested with state-of-the-art instruments such as Micro-FT. IR, TOF-SIMS, Py-GC and the heat simulation by adding water. The constitute, chemical composition and structure, characteristics and the potential generating hydrocarbon of coal measures source rocks have been studied in detail. The compositions of the Tertiary source rocks in the Xihu depression of East China Sea have been analyzed and it is confirmed that the Tertiary source rocks in this area mainly consist of Vitrinite, especially Vitrinite B (desmocollinite with hydrogen-rich) with a content up to 25～55%; Exinite with a content is often over 10% and Inertinite with a content usually less than 5%. The hydrogen-rich compositions are mainly Resinite and Vitrinite B. Especially the Resinite is abundant and usually has seepage bituminites at its edge which have genetic relationship with it. This is the direct symbol of hydrocarbon generating and accumulating by coal measures source rocks. Dull mudstone is mainly composed of mineral bituminite matrix and liptodetrinite. According to the characteristics such as the quality of generating hydrocarbon and the potential and content of generating hydrocarbon, it can be figured out that resinite and desmocollinite B are the chief hydrocarbon generating components of this coal measures source rocks. The chemical structures of resinite, cutinite, sporinite have abundant hydrogen-rich functional groups such as methyl, methylene, but resinite is comparatively abundant and is responsible for good hydrocarbon generating potential of this kind of source rock. A small amount of aliphatic functional group can be found in Desmocollinite B which explains the characteristics of generating more gas and less oil. According to the result of NIMR and TOF-SIMS, the hydrocarbon generating parameters of different macerals can be ascertained and estimated the relative importance of different macerals in hydrocarbon generating. The result indicates that the exinites in coal measures source rocks citribute most in generating oil. Resinite, one of most commonly found maceral in exinite is believed to have played the most important
role in generating oil. The importance of generating oil of democollinite is minor but it also has contributed to oil generating because of its rich content which makes up its limitation of quality. The studies of Py-GC of main macerals combined with the experiment of heat simulation by adding water have confirmed the hydrocarbon evolution track and the relative importance of different macerals in generating hydrocarbon. The result makes it clear that resinite generates lot of hydrocarbon before 300 ℃ while sporinite begins to generate hydrocarbon after 300 ℃ and the most peak period of generating hydrocarbon of the desmocollinite B is 400～500℃, which obviously lag behind the resinite and sporinite. We can establish hydrocarbon generating pattern of the Tertiary coal measures source rocks of the East China Sea Basin on the basis of the study of the evolution characteristics of hydrocarbon generating and the hychocarbon generating potential of main organic macerals. Compared with the coal of Perm-Carboniferous and Jurassic coals as well as Tertiary in Huangxian, Shandong province, the oil generating capacity of Tertiary coal measures source rocks of the East China Sea Basin is relatively lower, but the highest temperature of generating oil occurred earlier. This relates closely with the early stage of oil generates resinite. All of this indicates that the Tertiary coal measures source rocks of East China Sea Basin are more gas-prone than oil-prone, which determines the strategy exploration of natural gas. The study of the physic-chemistry and compound compositions of the oil and gas in the East China Sea Basin and the comparison with the relative characteristics of coal measures source rocks have indicated that both aspects have clear genetic relations, which explains why the coal measures source rocks are main source rocks of extracting oil and gas at present, especially why the resinite is main oil generating maceral. By studying the types, facies state, abundance, distribution, uniformity temperature and chemical composition(LAM) of organic inclusions, combined with the authigenic illite K-Ar dating in reservoir and synthetical study of the evolution of sedimentary structure and heat, we can ascertain the time and period of generation, migration and accumulation of the oil and gas in the Xihu depression. Tine result indicates that coal measures source rocks of Ming-Yuefeng formation in Taibei depression have only generated hydrocarbon one time before the formation of T°_2 structural layer with limited scale and amount. Coal measures source rocks of Huagang formation in the central Xihu depression have two times of bigger hydrocarbon generation with each being in T°_2, T°_1 structural layer, respectively, in which the period before the formation of T°_2 structural layer is the strongest. The Pinghu formation there had generated hydrocarbon one time before the formation of T°_3structural layer besides two times hydrocarbon generation actions in T°_2 and T°_1, but its peak hydrocarbon generating period was before the formation of T°_2 structural layer. The situation of western slope of Xihu depression is relatively unusual where the coal measures source rocks of Huagang formation is still in low mature and mature stages at present while the source rocks in Pinghu formation is in mature and high mature stages and the main hydrocarbon generation finished before the formation of T°_1, T°_0 structural layer especially before the formation of Too structural layer. According to the analysis of the relationship between the hydrocarbon generating time of different zones and analysis of structural evolution history, combined with the results of authigenic illite dating, we can ascertain that the earliest oil and gas accumulation of the uplift belt in Xihu depression happened in the Oligocene before 23Ma while in Huangyan zone it happened in the early and midle stage of Miocene. |
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