Research On Petroleum Accumulation In Mesozoic-Paleozoic,southern Jiangsu,lower Yangtze Region

Southern Jiangsu area is in the east of the low Yangtze area,which is on the north of the Wubao-Bozhen fracture, south of the Zhouwang-Wusu fracture and west of the Jiangning uplift. The exploration acrease is about 45,000km2. The area had come through many times reformation of tectonic cycle, the tectonic distortion of marine facies Mesozoic group and Protorozoic erathem were very intricate. The essay is based on extensive data collection and results of previous studies, combined with the core observation, lab test, and analysis of well-logs, in order to research the petroleum accumulation conditions of marine facies Mesozoic group and Protorozoic erathem, and took apart pool character and a period of time, and discussed control factor of pool, and took potential analysis of shale gas resource.There are four oil source rocks, two kind reservoirs of marine facies carbonate rocks and terrestrial facies clastic rocks, cap rock of muddy rocks and evaporitic rocks extensively develop. They lead to four types of reservoir formation combinations, which are Paleozoic source and Cenozoic reservoir, Cenozoic source and Paleozoic reservoir, stratigraphic unconformity reservoir and insider reservoir. It had five times courses of making hydrocarbon: the Caledonian period, the Hecynian-early Himalayan period, late Himalayan-middle Yanshanian period, late Yanshanian period and the Cumigration period. By the analysis of Huangqiao and Jurong oil-gas reservoir, we can draw the conclusion that there had been a massive destruction to the earlier oil and gas store during the late Himalayan-middle Yanshanian period in Sourthern Jiangsu area, the existing oil and gas store were formed by hydrocarbon regenerations of marine facies Mesozoic group and Protorozoic erathem..Based on the analysis course of making hydrocarbon and evolvement, oil and gas show and character of oil and gas store, after we researched the type of oil and gas store formmoment, and discussed control factors of form oil and gas store, then predicted and evaluated the favorable belt for oil and gas accumulation of Southern Jiangsu area. We consider there are multi-type of store that connected with marine faeies Mesozoic group and Proterozoic erathem. There are three main oil and gas pool’s types that are Paleozoic source and Cenozoic reservoir, Cenozoic source and Palcozoic reservoir, Paleozoic source and Paleozoic reservoir. Huangqiao carbon dioxide gas store is divided to mantle souce gas & organic gas and inorganic gas pool’s types. There are two mements of form oil and gas store that Caledonian to Indosinian before and late yanshanian to Himalayian, thereinto. Formative oil and gas store in the last moment have real sense. The main control factor of forming oil and gas store include three ways: One is that Indosinian to early yanshanian movement breached early oil and gas store; Two is that the center of making hydrocarbon control distributing of oil and gas store, the center of later making hydrocarbon have important sense. Three is that the overcast of terrestrial Mesozoic group have important action for current oil and gas stores.By the analysis of hydrocarbon source rocks, we can draw the conclusion that the Mufushan group of lower Cambrian and Longtan group & Da long group of upper Permian were the layers with richest organic shales in Southern Jiangsu area. It is estimated by volumetric method that the shale-gas resources amount of the lower Cambrian is 1.23×1012m3 and the shale-gas resources amount of Longtan group & Da long group in upper Permian is 1.93×1012m3, which indicates a great shale-gas resources potential. According to prelimunary prediction, the favorable areas for shale-gas exploration of Mufushan group in the Southern Jiangsu area is Taizhou-Jurong area and Yixing-Suzhou area; while the favorable areas for shale-gas exploration of Longtan group and Dalong group in the Southern Jiangsu area is Jurong-Nanjing area and Yangzhong-Taixing area.