| The study area is located in the Jiyuan area of the central and western Ordos Basin.The structure spans the Shanbei slope and the Tianhuan depression.It is a key area for petroleum exploration and development in Changqing Oilfield.This study comprehensively used data from drilling,core,logging,seismic,logging and analysis and testing.Start with fine stratigraphic division and contrast.The structural characteristics,sedimentary facies characteristics,and reservoir characteristics of the Yan 9 formation of the study area were systematically analyzed and discussed,and the petroleum enrichment regularity of the Yan 9 reservoir were summarized.The sedimentary source of the Yan 9 formation in Jiyuan area is from the northwest,and the sedimentary subfacies are delta plains.There are three types of microfacies:diverted river channels,natural dikes and inter-swamps.Reservoir rock types are mainly feldspar sandstone and lithic feldspar sandstone.Kaolinite and carbonate rocks are the main types of interstitials.Compared with cementation,compaction is the most important reason for the decrease in porosity of the reservoir.Corrosion of aluminosilicates such as feldspar and turbidite has improved the porosity and permeability of the reservoir.The diagenesis stage is generally in the early diagenesis stage B.The average porosity of the reservoir is 14.65%,and the average permeability is 20.25×10-3?m2.Good correlation between porosity and permeability.The average face rate of the Yan 9 formation reservoir in Jiyuan area is 15.50%on average The types of pores mainly include intergranular pores,intergranular dissolved pores,intragranular dissolved pores,intergranular pores,and microfractures.The throat types are mainly constricted throats and flakes.According to the mercury lamination parameters and porosity and permeability properties,the pore structure is divided into three types.The three types of pore structure have different fractal characteristics and concentrated distribution intervals of pore throat radius.SEM images were analyzed based on Image J software,and the pore size distribution of different pore types was quantitatively analyzed.The main structure of Yan 9 formation of the Jiyuan area is a large monoclinic inclined to the west.There are multiple rows of small nasal uplifts on the top surface of each sandstone group with good inheritance.Local uplift has an important impact on petroleum accumulation.The source of the Yan 9 reservoir is mainly from the Chang 7oil shale of the Yanchang Formation.The Yan 10 braided channel sandstone and the irregularities in ancient landforms are the main migration channels for petroleum migration into the Yan'an Formation.Petroleum are migrated to the structural traps or lithologic-structural traps to form reservoirs,and the delta plain tributary channel sandstone are the main reservoirs.This study is of great significance to improve the drilling success rate and increase reserves and production of the Yan 9 reservoir in Jiyuan area. |
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