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Study On Sedimentary Characteristics And Subtle Traps Prediction Of Dongying Formation In Shenxian Depression, Jizhong Sub-basin

Posted on:2011-03-30Degree:MasterType:Thesis
Country:ChinaCandidate:X C SunFull Text:PDF
GTID:2120360302492819Subject:Mineral prospecting and exploration
Abstract/Summary:PDF Full Text Request
Since Paleogene, the lake basin was small in Shenxian depression of Jizhong subbasin. The development of Shenxian depression was controlled by two contemporaneous faults and its rift system was complicated. During the deposition of the Dongying formation, inherited structures were prevalent. Lake basin was at the transformational stage of fault depression when the fault was developed with small amplitude and moderate tectonic action and more than 1000m fluvial sediments were deposited. The main type of sandstone was fluvial channel sand. At the end of Dongying formation, Shenxian depression had regional uplift by the impact of regional uplift action and suffered denudation, which formed regional unconformity. At this time, structural framework was essentially formed.After several years of exploratory development, Shenxian depression has entered the high mature stage of exploration. Structural trap was the main trap discovered previously and lithologic trap was found less, which restricted the further exploration. Therefore, in this thesis, following the "superposition" path the petroleum play were determined on the basis of sequence features and sedimentary facies distribution characteristics, combined with facies belt, fault development features, hydrocarbon distribution and mudstone capping formation .subtle traps were found by the correlation theory, which had important theoretical and practical significance for further exploration and production. The achievements of this thesis were as follows:1) On the basis of the full analysis of previous research results and regional geology setting, Dongying formation was divided into three long-term cyclic sequences and six medium-term cyclic sequences applying the theory of high-resolution sequence stratigraphy and using the data of well cores, logging profiles, logging curves, seismic and so on. Following base level cyclic sequences subdivision of different hierarchies in single well, the high resolution chronostratic framework was established by isochronic strata correlation in the long-term cyclic sequence, which laid a foundation for studying depositional system.2) The provenance of Dongying formation has multiple directions by the analysis of Regional geological data, palaeogeomorphology, rock and mineral composition data. The provenance has four major source directions: north, southwest, south, southeast.3) Shenxian depression Dongying Formation facies were mainly dominated by braided fluvial, the meandering fluvial and the braided river delta were also developed. In 1st member and 2nd member of Dongying formation, the depression region covered by the braided fluvial, channels were developed very well, and the channel distribution was very continuous. The braided fluvial was mainly developed in the 3rd member of Dongying formation, the braided river delta was only developed in the Yuke and Hubei area, and the delta plain was the main fades, the delta front and the lacustrine deposits was very small.4) After the study of the microfacies of 1st member and 2nd member of Dongying formation. Five types of the microfacies were developed, they include channel bars, point bars, flood sand, crevasse splays, flood plain. The microfacies distribution had the transition characteristics of the meandering and braided rivers.5) Under the guidance of the subtle traps theory, integrated four major elements: sedimentary facies distribution, fault characteristics, distribution of source rocks and shale cap, to predict play and subtle trap zone of the Dongying Formation, the play distribution was controlled by sedimentary facies and fault obviously. On the basis of the evaluation of the play, two subtle traps were predicted.
Keywords/Search Tags:sequence features, sedimentary facies, play, subtle traps, Shenxian depression
PDF Full Text Request
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