| Based on oil and gas exploration work is paleogeographic petrographic study.Over the past decade, in the upper Yangtze region of ordovician lithology, sedimentary facies and hydrocarbon source rock, reservoir and other advances a series of research, but research in the ancient geography, still is mostly qualitative, not quantitative, restricts the oil and gas exploration work.Therefore, the study area is overall, system and in-depth qualitative quantitative lithofacies palaeogeographic research for oil and gas exploration in detail on the basis of geological data is necessary.The study area from east longitude102°to102°, the area of24°to the north latitude33°.Geographically, in the study area northwest TianQuan-wenchuan-guangyuan-hanzhong is bounded, southwest to have succeeded-kunming-TianQuan is bounded, southeast of changsha-suijiang ning-have succeeded as the boundary, north to hanzhong fangxian county-xiangfan is bounded.In jiangxi, yunnan, sichuan, shaanxi, chongqing, participation, guizhou, guangxi, hunan, hubei and other nine provinces and municipalities.Research area of the northwest of longmen mountain nappe belt, for the qinling dabie orogenic belt in the northeast, southeast of jiangnan xuefeng thrust uplift, for DaLiangShan fold belt in southwestern and northwestern guizhou fold belt.Also some scholars from the viewpoint of basin, referred to as upper Yangtze basin.On the basis of predecessors’ research, based on the measured profile and observation section of upper Yangtze region on ordovician stratigraphic classification and correlation.The qiantang river and YiGuShan order in the study area have been development, and has strong comparative.YiJiaShan order can be divided into the pagoda and temple slope group, pagodas and inkstone tile mountain group, temple slope aka Hu Le group, cross-stitch shop and field dam group.Qiantang river can be divided into five mountains and LinXiang group, this text also named tianma mountain group, white water group and the latent group, also known as wong nei subdivided LinXiang group, countless CaoGou group and the chrysanthemum.Text is a research and upper part of the guanyinqiao group for the nantes order, part of the development in research area.Field observation and indoor study, the rock type of the ordovician in the study area is relatively simple, mainly for the carbonate rock, clastic rock and silicon.Among them, mainly carbonate sedimentary;Clastic rock times, the main development in five mountains group;Silicon rock relatively at least, are generally only see and in group five mountains.With limestone in the carbonate rock landslide, is containing different amounts of biological mud SPAR more limestone, wide development in the whole work area;Development of dolomite is limited, only the west garden in sichuan chicken mountain and prosperous regions in sichuan deer see and cross section.Among them, the fine-ZhongJing dolostone, mud SPAR limestone and argillaceous siltstone mainly distributed in restricted sea platform.Biological mud SPAR limestone, marl and nodular marl distribution in the open sea platform and carbonate shelf, shelf carbonate (see also containing calcareous shale.Calcareous shale, calcareous mudstone, containing graptolite shale and containing silty shale distribution in argillaceous shelf.Siliceous shale and siderite slope shale distribution in the deep.Others are distributed in the basin facies.Ordovician thickness changes on the study area is larger, ranging from several meters to tens of meters. And formation thickness is one of the largest pagoda group in the study area, the thickness is in commonly10meters to dozens of meters, is the study of sea basin in the area’s most widely distributed, lithofacies and sedimentary period of the most stable.Thickness of strata thickness is the smallest LinXiang group, generally within a few meters to10meters, widely distributed in the study area. Late ordovician in the study area mainly five kinds of sedimentary type, respectively is: ancient land (denudation area), carbonate platform facies, wide sea continental shelf facies, the deep slope and basin facies.In the carbonate platform phase, can be divided into restricted sea platform and phase and open platform subfacies level subfacies.In the wide sea shelf phase, is divided into carbonate shelf and phase and argillaceous shelf subfacies.While the basin facies can be divided into carbonate basin subfacies, marly basin subfacies and silicon argillaceous basin.In addition, the development of carbonate platform facies have shoal microfacies. Temple group is given priority to with wide sea continental shelf facies, slope pagoda group most of the region belong to the middle of the basin facies carbonate basin deposition, LinXiang group mainly in the middle of the basin facies marly basin deposition, this text set in the middle of the basin facies silicon argillaceous basin deposition is given priority.The main body of upper Yangtze area in a constant sea into the process. Since the temple slope sedimentary period to five mountains sedimentary period, in addition to the basin, northwestern margin of keep shallow water environment, upper yangzi area main body by sinking gradually overall sinking in the carbonate platforms for the wide sea continental shelf, carbonate basin, marl basin, so that the final settlement for under the carbonate compensation interface silicon basin of the shale.Based on the petrological study, the selection and statistics that can be independently reflect the characteristics of the sedimentary environment in a single factor such as formation thickness, deep shale content, deep-water carbonate content, shallow water carbonate content, granular carbonate etc., draw the corresponding single factor maps.Then in combination with regional geological data, and other quantitative and qualitative data, to conduct a comprehensive analysis and comprehensive judgement, draw out four period of the upper Yangtze region late ordovician paleogeographic map, and the upper Yangtze basin of late ordovician sedimentary environment from west to east, in turn divided into land, carbonate platform and basin.Among them, give priority to with basin, is widely distributed in sichuan region, xing mountain-yichang-shek mun-xiushui area and hanzhong xixiang-west region;The carbonate platform is distributed in the north and west in the study area; Slope is located in the transitional area of carbonate platform and basin, for ring slope, except only temple slope period, distributed in the east in the study area;Clastic rock platform is limited, a rectangular distribution in east yunnan west, western sichuan, and guizhou, only development in five mountains group;While land limited located in the north, west, widely developed in the south.On the basis of lithofacies palaeogeographic, combined with the analysis of the related test data, analysis of the upper Yangtze region of late ordovician, reservoir, cap, condition.Favorable hydrocarbon source rocks in the study area for shale and quartzite, a generative hydrocarbon facies basin, followed by slope.Has gone through a lot of hydrocarbon expulsion process, so the key to oil and gas prediction is the distribution of reservoir rock, trap conditions and the renovation of the late damage.Reservoir rock in the study area are mainly distributed in the border areas of research area, and most of the study area is the hydrocarbon source rock distribution area, reservoir rock is very close from the hydrocarbon source rocks, this brings to the oil and gas accumulation of the advantageous condition.Reservoir rock is trap conditions at the same time, the guanyinqiao section can form lithologic trap (surrounded by hydrocarbon source rock), karst rock can be formed and unconformity surface related stratigraphic trap (it is unconformable surface), oil and gas can be achieved by unconformity surface and the reservoir rock side to the margin of basin secondary migration, according to the geological conditions of speculation, the edge in the study area of potential reservoir rock distribution area may become a research area of oil and gas prospect area. |
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