| This paper studies the Triassic System of Luoyi District and mainly focuses on the upper Triassic. With the theoretical guidance of sequence stratigraphy, sedimentology and reservoir geology and based on the building of sequence stratigraphic framework, this paper analyzes the spatially distributing feature of sedimentary system in Triassic System combing the data of well logging, drilling well, core and outcrop. On the study of reservoir, this paper mainly uses the data of casting thin sections, sem to study the characteristics of reservoir. This paper ensures the controlling factor of the reservoir and classification of the reservoir. In the end, this paper predicts the favorable facies belt combing the study of characteristics of the sedimentary and reservoir. This paper altogether includes six chapters:The first chapter introduces the objective and significance of topic selection and the research situation on the sequence strarigraphic, sedimentology, and reservoir of the study area. The exploration situation and existing problems are also described. This paper uses the comprehensive analysis of sequence-sedimentary-reservoir. With the help of previous study, this paper develops the sequence strarigraphic framework, studies the spatially distributing characteristics of the depositional system and analyzes the reservoir characteristics. These study all contribute the division of the favorable facies belt.The second chapter introduces the regional geological characteristics of Luoyi District. Luoyi District belongs to the southern north China basin, a Meso-Cenozoic basin developed on the basement of the North China Platform at later Indo-Chinese epoch with the northeast trending. Luoyi District experienced multi period tectonic evolution after the sedimentation in the Triassic stage, such as the extrusion movement in late Indo-Chinese epoch, the uplift and erosion in Yanshan stage, the extensional faulted depression in early Himalayan stage and the depression in late Himalayan stage. Luoyi District experienced the river-lake-delta sedimentation in Triassic stage and the extrusion deformation in Yanshan stage. The four areas of Luoyi District which includes Luoyang, Yiyang, Luoning and Yichuan accept thick sedimentation in Lower Tertiary as the fault depression of Himalayan movement. Nowadays, the residual layer of Triassic mainly distributes in Yichuan, Yiyang and Yima area of Luoyi District.The third chapter mainly analyzes the construction of sequence stratigraphic framework. Based on the tectonic background of this district and the previous sequence stratigraphic division, this paper studies the typical seismic reflection characteristics and the identification marks of the sequence boundaries in well logging as well as the fine calibration horizon, and this paper finally constructs the isochronous stratigraphic framework, divides the Triassic into thirteen third-order sequence and summarizes the sequence style and the characteristics of different third-order sequence. This paper also identifies the sequence boundaries and framework on the outcrop. On the basis of construction of the sequence framework and the time-depth conversion, this paper finishes the residual stratum thickness of Triassic and analyzes the distribution features. In the end,this paper summarizes that the distributing area of the residual thickness of the upper Triassic is small but with thick stratum, while the distributing area of the middle and lower Triassic is big but with thin stratum.Sedimentary system is studied in the chapter four by means of the sedimentology research method of "point-line-plane-body-time". Starting from the core and outcrop observation, including color, granularity, separation, rounding, fossils, microelement, graded and bedding,the paper analyzes the regional sedimentary fancies at point, which laid the foundation of establishing the corresponding relationship of lightfacies-electrofacies-sedimentary facies. It is three types of sedimentary systems:meandering river, delta and lake that can be mainly distinguished in the Luoyi District in the research zone from single well sedimentary facies, connecting well sedimentary facies, electrofacies analysis and distribution system of sand. The subfacies which are identified from the meandering river include riverbed, embarkment and floodplain, the subfacies which are identified from the delta include delta plain, delta front and prodelta and the subfacies which are identified from the lake include shore shallow lake and semi-deep lake. This paper analyzes the source system with the data of imaging logging and dip logging. The result shows the main sources of the upper Triassic are from the Mount Xionger in southwest of Yichuan city and the Mount Zhongtiao in northern Yima city. In the early and middle Triassic period, the north of the district is higher than the north, and the east area is higher than the west, the main source is from the north. This paper finally ensures the distributing characteristics of sedimentary facies in Triassic and the meandering river mainly develops in the early and middle Triassic and the delta and lake mainly develops in the late Triassic. The lake level gradually grow from the early Triassic to the late Late-Triassic.The fifth chapter studies the characteristics of the reservoir. By using the data of casting thin sections, sem, analysis and test data of core, this paper analyzes the rock and mineral characteristics, the diagenesis, the pore structure, the four-property relationship and the physical characteristics. The rock styles of the upper Triassic are lithic arkoses, feldspathic litharenite sandstones and lithic feldspathic sandstones. The pore types are interparticle dissolution pore, intragranular dissolved pore and micro fracture and the reservoir belongs to the low porosity and ultra-low permeability reservoir. The main diagenesis types are compaction, cementation, dissolution, replacement. It is the compaction and cementation that reduces the primary pore space, while dissolution and replacement generated secondary porosity that improves reservoir quality. The low porosity and ultra-low permeability reservoir is controlled by the influence of the diagenesis, sedimentation and the tectonic progress. Through the analysis of the influence of the sedimentation to the reservoir,this paper believes the subaqueous distributary channel, the mouth bar and the distal bar could form better reservoir bodies. In the end,this paper classifies the reservoir of the upper Triassic based on the current classification and divides the reservoir of this district into four types. The I type is low permeability reservoir with the porosity of10%～12%and the permeability of1～19.1×10-3μm2. The Ⅱ type is ultra-low permeability reservoir with the porosity of8%-10%and the permeability of0.3-1～10×-3μm2. The III type is super-low permeability reservoir with the porosity of3.3%～8%and the permeability of0.08～0.3×10-3. The Ⅳ type is non permeability reservoir with the porosity less than3.3%and the permeability less than0.08×10-3μm2.The sixth chapter is about the division of favorable facies belt.Considering source rocks, reservoir, seal, accumulation as well as the matching relations between the various elements, the favorable facies belt of each layer of upper Triassic are divided. The favorable facies belt of the study area are mainly located in the areas between the delta front and the semi-deep lake, and the favorable reservoir mainly distribute in subaqueous distributary channel, mouth bar and distal bar. |
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