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Structure Evolution And Hydrocarbon Potential In Ruoergai Area

Posted on:2007-01-04Degree:MasterType:Thesis
Country:ChinaCandidate:Q Y SongFull Text:PDF
GTID:2120360182982558Subject:Mineral prospecting and exploration
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Ruoergai area lies in the south of Xiqinling. And the Kunlun-Qinling orogeny is themost significant fault-intracontinental subduction zone in China mainland. The orogeny tendsfrom east to west and it westwards to be linked to the Middle East, Central Asia. The entireframework is quite similar to the Middle East pattern where a great deal of oil&gas filedswere discovered, they all belong to Thetys area. Basement of Ruoergai area is similar toYangtze massif. Ruoergai area was a passive continental margin that face light pitchnorthward in early Palaeozoic, developed the rock series of the basin facies and shelf faciesover 5000m thick..it was carbonate tableland in late Palaeozoic, and widely covered marinefacies layers of Triassic. So the area is the important prospect of oil and gas.With Regional seismic profiles, the major structural layer systems are divided anddissect structure features in Ruoerge area. In the process of its evolution, it causedjuxtaposition of different structure-layer composites in the horizontal direction andsuperimposition of different structure-layer composites in vertical direction. At the evolutionof its regional structure, it Experienced two major tension-compression stages of development.First, after the old China landmass dismembered in late Proterozoic, the Tianshan-QilianMountain-Qinling Ocean, which separates the Yangtze massif from North China massif,formed in early Palaeozoic, and passive continental margin basin developed in the north ofRuoergai area. The Yangtze landmass collided with North China landmass due to Caledoniansubduction which happened after the ocean basin closed with Paleotethys subduction atEarly Palaeozoic. At last it developed Caledonian orogeny and caused borderland basinreversing. Second, from late Palaeozoic, with Paleotethys expansion and in the west of theYangtze landmass rifts appeared and then some small ocean crusts generated in the rifts. Thewest(south) of Ruoergai area was growing pull-apart continental margin and in basins itdeveloped turbidity current deposit . Otherwise with Paleotethys closing in late Triassic period,the pull-apart continental margin reversed in Indo-China movement creating Indo-Chinafolded orogeny. With the new tethys diving, India landmass collided with the Eurasiancontinent and the area turned to be uplifted together with Tibet Plateau. Eastern boundary ofRuoergai massif affected by the Longmenshan orogeny and developed intracontinental foldedorogeny, at last formed the structure framework now. In this structure conversion process, itshows multicycle characteristics in the area.The area lies in the south of the main oil zone of early Palaeozoic, is a belt of transitionfrom basin facies to continental shelf facies, it has favourable conditions for genetic potential.The layer of late Palaeozoic has not come out to the day. But according to the regionalenvironment analysis, it is a stable carbonate rock tableland. At the same time, the MT sectionthrough the southwest of the Jiuzhi-Aba-Longriba shows that there are late Palaeozoic layersand they are kept well at the region, covered by Triassic layer. In the late Palaeozoic layer,there are many carbonate reef, bank and sand to grow the reservoir bed that went through theinterruption in deposition, fresh water leaching and corroding to improve the conditions ofreservoir and fracture without displacement in early Carboniferous Period and late PermianPeriod. Constructed the carbonatite reservoir bed of late Palaeozoic.Based on the structure evolution and relationships of oil source rock, reservoir bed andcover rock analysis in Ruoergai area, we can draw a conclusion that Tangke uplift zone andHongyuan hollow zone are exploring target of profitability.
Keywords/Search Tags:Structure evolution, Tectono-stratigraphical division, Structure style, Array of oil source rock, reservoir bed and cover rock, Hydrocarbon potential
PDF Full Text Request
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