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A Study On Tentonic Characteristics In The Zifusi Sag Jiangling Depression

Posted on:2013-06-02Degree:MasterType:Thesis
Country:ChinaCandidate:L ZhangFull Text:PDF
GTID:2230330374976741Subject:Mineral prospecting and exploration
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Jianghan Basin is located in Hubei province, central of the Jianghan Plain,an area of36,360square kilometers,which is a typical inland salt lake fault basin in east of China and can be divided into11depression and4salient. Jiangling depression lying in the Jianghan Basin southwest, is the largest secondary tectonic unit in Jianghan Basin. Jiangling Depression have the tectonic framework ofblock shape in north-west direction and stripe shape in north-east directionas Wancheng fault as the boundary, and it developed a number of the fault depression, overall showing the tectonic framework of more uplifs and more depressin.Jiangling Depression get a certain breakthrough through years of exploration and research, but for a long time was thought that Meihuaiqiao Subsag had the best hydrocarbon generation, so the degree of exploration is very unbalanced, the understanding of sag’s hydrocarbon potential is inconsistent. The study area is located in Zifusi Sag and its surrounding, eastern of Jiangling Depression, which is one of the favorable hydrocarbon rich zones. But because of lacking of drilling data in Zifusi Sag, there has not been a clear understanding of the size and potential of hydrocarbon generation. Therefore, understanding and evaluation of exploration potential of Zifusi Sag, has very important significance for evaluation of hydrocarbon potential and finding oil and gas rich region of Jiangling Depression. Among them, the structure research is the basis of the oil and gas geological system, and the tectonic activity plays a very important role in controlling all aspects of hydrocarbon accumulati-on.This thesis have analyzed the structural characteristics and tectonic evolution of the research area on the premise of full collecting of the regional tectonic and sedimentary data, seismic data and drilling, logging data in study area. Based on the seismic interpretation of the measuringline in study area, the plan structural characteristics, fracture developmental characteristics and local structural features have been study, and the tectonic framework of Zifusi Sag have been divided; Based on distinguishing the unconformity and dividing the sedimentary cycle to divide the tectonic evolution stages of the study area, the characteristics of tectonic evolution have been researched according to recovery of the thickness of eroded strata by Magara’s mudstone SDT method and to make structural history profile; The relationship between the tectonic activity and oil and gas including the tectonic activity and the development of hydrocarbon source rocks, the effect of oil-gas migration and the local tectonic influencing on hydrocarbon accumulation and so on have been analyzed under the guidance of the understanding of the structural characteristics and tectonic evolution.Zifusi Sag and its surrounding develop lots of faults with varying lengths and differ in size of fault throw, and there are developed two sets of fault systems:the normal fault in NNE-NE-EW and the reverse fault in NW-SN. The distribution of these two sets of fracture has a strong regional:the reverse fault mainly distributed in Fuxingchang area and the normal fault developed in the most of the regions.The fracture development is roughly divided into three stages of the late Yanshanian, early Himalayan and late Himalayan. The region had been developde four kinds of local tectonic type including syngenetic structure, salt structure, inversion structuread volcanics structures since the Cretaceous period:The syngenetic construct can be divided into three subtypes: syngenetic fault, reverse drag anticlines and fault blocks, and they had been controlled by the growth fault.The syngenetic constructed had developed adjacent to the distribution of syngenetic faults in research area as Zibei fault as the most typical; Inversion structures, including reverse fault, extrusion anticline and extrusion fault block, mainly formed in the late Himalayan, which were formed because of the early normal faults reversing, and were mainly distributed in Fuxingchang area; Salt tectonics can be divided into three sub-types:salt pillows, salt anticlines, salt ridges, according to the degree of development, and were mainly distributed in Fuxingchang and Shashi area of Jingzhou anticline, which were formed in the early Jingsha deposition period, set in the end of the Neogene; Volcanic structure had been located in Zinan, Zibei fracture nearby as Jinjiachang structureas as the most typical. The study area of volcanic activity mainly occurred in Xingouzui deposition.Tectonic units of the study area have been divided into Jingzhou Anticline Belt, Qingshuikou Syncline, Zifusi Sag and Gongan Monoclinal Zone fromnorth to south considering the distribution of control depression fracture, the distribution rule of kinds of structural styles, thickness variations of the source rock sand the overall pattern of tectonic.The erosion thickness of the end stage of Jinghezhen of27wells in different tectonic zone have been restored through the Magara’s mudstone SDT method, and the results have suggested that the erosion thickness comparatively large in uplift zone and slope zone. Through the analysis of the structural history profile showing that, part of the faults had started activities before Jingsha deposition because the stress field changed from compression into the north-east tension.Cretaceous sedimentary strata had been formed structural pattern of south lift,middle bend, north gentle slope impacted by previous fracture; Faults activity changed from strong to weak between Jingsha and Xingouzui deposition, and the overall sediment to accept deposition at Late Xingouzui deposition; When Jingsha deposition, controlling deposition faults intensified activities, and the fault depression had been a scale;Faults activity had been weakened again,and the tectonic framework basic shaped at Qianjiang and Jinghezhen deposition;formed the basic shape of structural pattern.Strata uplifted to subject to intense erosion at late Jinghezhen deposition.Later,the overall strata sedimentated during Neogene and Quaternary deposition, formed the modern structural pattern.Based on the distinguishion of unconformity and sedimentary cycle and combine with the results of erosion thickness recovery and analyzeing of the structural history profile, the tectonic evolution have been divided into three stages:Late Cretaceous-Early Eocene (K-E2) rift formation phase, Middle Eocene-Oligocene (E2-E3) rift formation phase and Neogene to Quaternary (N-Q) regional depression phase. Each tectonic cycle can be divided into two substages for faulted period and rift-subsiding period under the control of the change of tectonic stress and tectonic activity, and each structure has its own tectonic and sedimentary characteristics.In the role of the tectonic evolution, tectonic framework of Zifusi Sag had different change and finally set, forming the today’s outlook.Tectonic activities were happened frequently in study area, forming variety of constructed types, so the relationship between structures and oil gas is very intimate. Fractures of controlling sag have controlled the thickness and distribution of the source rocks, and tectonic evolution have directly controlled the oil sourceconditions through effecting the history of the thermal evolution of source rocks; Developed fracture system have provided favorable channel for the migration of hydrocarbon source rocks in study area, and the migration pattern was also infinitevariety, including lateral stepwise migration and vertical migration and so on; The distribution and supraposition of four local structural types developed in Zifusi Sag forming a large number of structural traps, which had playde an important role in accumulating the oil and gas, meanwhile the distribution of structural traps have also directly affected the distribution of oil and gas, and the vast majority reservoirs of the study area are constructed reservoirs.
Keywords/Search Tags:Zifusi Sag, Structural interpretation, tentonic characteristics, tectonicevolution, oil-gas significance
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