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Deposition System And Oil Accumulation Research Of Yanchang Formation In Triassic, Ordos Basin

Posted on:2005-11-07Degree:DoctorType:Dissertation
Country:ChinaCandidate:H YangFull Text:PDF
GTID:1100360155458544Subject:Paleontology and stratigraphy
Abstract/Summary:PDF Full Text Request
This paper investigates the Yanchang formation in Triassic system of Ordos basin, using theories as sedimentology, petroleum geology, geophysics, et al., based on abundant outcrop sections, well drilling and seismic data. This paper also systemly investigates the characteristics of deposition systems in Ordos basin, sedimentary microfacies of the leading pay formations, sand bodies and its distributions, and reservoir characteristics, adopting the technique methods of academic research combined with practice research and macroexaminations combined with microexaminations. From the analysis of paleocurrent data, light minerals data and heavy minerals data of Ordos basin's fringe , we conclude that main deposition systems developed in Yanchang Formation include northeast and southwest deposition system. The distributions of the sand bodies are controlled by deposition system. Southeast deposition system's sand bodies' configuration that have low component and textural maturity presents a band shape of east-west and northeast-southwest trend from Huanxian to Zhengning. Northeast deposition system's sand bodies which have a good continuity presents a northeast-southwest trend in the plane .Having an overview on the evolvement from member 10 to member 1 of Yanchang formation, Ordos lacustrine facies basin expanded gradually and then shrinked. The siliciclastic Yanchang formation which characterized by fluvial-lacustrine facies was cumulated in the period of continuant sagging and stable subsiding of Ordos basin. Ordos lacustrine facies basin expanded to its height at member 7 stage, Then, the basin came to shrinking as the continuant infilling of fluvial. This paper discusses the developoment characteristic, lithology and properities of different delta of different stage, and analyses and contrasts the oilness of different delta.Delta sandstone and the regional big westleaning monocline make of a best combination. Bottomland, swamp and bight depositions above the sand bodies make for the accumulation and preservation of oil and gas. Turbidites at the frontpage of braid river delta sand bodies and fan delta front sand bodies are favorable reserviors for oil and gas accumulating. Accumulating patterns of different delta deposition system are put forward. Based on the deposition systems and sand bodies forcasting combined with accumulating rules, potential areas can be identified.
Keywords/Search Tags:Ordos basin, Triassicm, Yanchang formation, deposition system, delta, sedimentary facies, petroleum deposit, turbidite fan, sand bodies distribution, potential area
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