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The Tectonic And Sedimentary Evolution And Its Relationship To Gas Accumulation Of Lower Paleozoic In Ordos Basin

Posted on:2004-04-01Degree:DoctorType:Dissertation
Country:ChinaCandidate:B DangFull Text:PDF
GTID:1100360092998612Subject:Mineral prospecting and exploration
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Ordos Basin is a polycyclic superposition basin that is formed in an earlier geological history and has experienced a longer evolution. At the same time, it is the second largest sedimentary basin on land in China that possesses abundant oil and gas resources and has bright prospects in oil and gas exploration. It has been becoming one of the important tactical areas in oil and gas exploration in China. The amount of oil and gas resources and the degree up which it is proven will directly influence the Chinese petroleum industry. In order to summarize the rules of hydrocarbon accumulation and distribution in Ordos Basin objectively, it is necessary to research the tectonic sedimentary evolution and the accumulation of natural gas.The research base on the theories of plate tectonics, use the method that oil and gas basin is analyzed integrally, dynamically and comprehensively, and obey the principle that intersection, superposition and compound of the three tectonic domains (the paleo-Asian, the Tethyan and the circum-pacific) control and influence the formation and development of Ordos Basin in different tectonic stages. The investigation in the field was combined with research indoors. By classifying tectonic sequence, confirming corresponding prototype basin, analyzing paleo-tectonic stress fields in different periods, plotting correlative tectonic map based on 297 explore wells, and analyzing the traits of the remaining depressions producing hydrocarbon and their migration rules in the Ordovician, the author studied the basement of the basin; the fault system of the basin; the tectonic-sedimentary evolution of the basin and its circumference areas; the prototype basin and corresponding dynamics background; the paleo-tectonic pattern and its evolution in the layers of producing gas in different periods of Ordovician; the superposition relationship among the different period basins formed by different stress fields; the reformation of the basin and the formation, redistribution and final emplacement of the gas pools. Some conclusions are listed as follows:The plateform cover cap of Ordos Basin and its circumference areas can be divided into five tectonic sequences. The tectonic evolution of Ordos Basin can be classified in six stages: the basement formation phase (from Archeozoic to Paleoproterozoic); the aulacogen phase (from Mesoproterozoic to Neoproterozoic); the North China continental sea phase (from Sinian to early-Paleozoic); the north china intracratonic depression phase (from late-Paleozoic to early Mesozoic); large Ordos inland basin phase and the formation of independent Ordos Basin (Mid-Late Mesozoic); fault basin phase around the Ordos Basin (Cenozoic).The different evolution stages of tectonic sedimentary development were controlled by the different tectonic dynamic systems. The main continent rift developed in Mid-Late Proterozoic; the paleo-Asian tectonic dynamic system played an important role in the Paleozoic period; the combination of Tethys-paleopacific tectonic dynamic system influenced the basin in Mesozoic. During that period, the Tethyan dynamic system affected the basin in the early stage (T) while paleo-pacific dynamic system affected it in the latter stage (Js-K); the new Tethyan -circum pacific tectonic dynamic system dominated in Cenozoic period.The fault system of the Ordos Basin includes the basin-surroundings fault system, the basement fault system, the platform cover fault system, and the platform cover fracture system. The basement fault system was developed by two sets, the NE direction fault and the EW direction fault, which closely connect with the oil and gas accumulation.The fracture system was mainly made up of vertical fractures which were developed in different phases and showing themselves by plane X-conjugate joint systems. The current fracture character is the result of the Himalayan movement. The development of the fractures has obviously improved the character of reservoirs of Ordos Basin and controlled the accumulation of oil and gas.There...
Keywords/Search Tags:Ordos basin, tectonic sedimentary evolution, fault system, tectonic stress fields, Paleo-structure, lower Paleozoic, Ordovician, accumulation of natural gas
PDF Full Text Request
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