| The research of reservoir geological characteristics is the core component of oil and gas field development.Through the fine study of Reservoir,it solves the difficulties such as multi-layer and complex oil and gas enrichment laws in the study area,which lays a foundation for fine reservoir description in the later stage,provides a strong scientific basis for oil and gas field development,and is conducive to putting forward efficient development technology policies and development adjustment programs.The Yanwu Oilfield is located in the south of the two tectonic units' of the Tianhuan depression of the Ordos Basin,which belongs to Zhenyuan County,Qingyang City,Gansu Province in regional geography,and has become a stable block in recent years.In this paper,the Yan 7 and Yan 8 oil-bearing formations in the S191 area of Yanwu Oilfield are taken as research objects.Under the guidance of reservoir geology and sedimentary petrology,according to well logs,production data,test analysis data,and based on the previous research results,the geological structure,sedimentary characteristics,reservoir characteristics and reservoir types of the area were studied in depth.Through these researchs,this article has arrived at some conclusions:(1)Under regional background,S191 area of Yanwu Oilfield develops a NW-SE anticline structure as a whole,and multiple noses are developed on the basis of the anticline structure.The stratum in the southeastern part of the study area is slow and the stratum in the northwest is steep.In the case of using the coal seam as the marking layer,the Yan 7 and Yan 8 oil-bearing formations are all divided into four sub-layers.(2)Yan 7 and Yan 8 in the S191 area of Yanwu oilfield are braided river delta plain subfacies.The River course in the Yan 8 period is more developed than Yan 7,and the sand body is also obviously extended than Yan 7 period;Distribution of sand body of distributary channel sedimentary microfacies is thicker and its scale is larger.And the overall source direction is stable.(3)The lithology of the Yan 7 and Yan 8 reservoirs in the S191 area is mainly medium-grained,medium-fine-grained feldspar quartz sandstone,and the lithic feldspar quartz sandstone is partially contained.The interstitial material is mainly composed of iron calcite,siliceous and hydromica.Intergranular pores are the most important pore type,and the pore throat structure is single and has very good fluid storage capacity.(4)The overall evaluation of permeability heterogeneity in S191 area of Yanwu oilfield is medium to weak.Due to the development of thick composite sand bodies,the upper and lower layers of the sand body are superposed,resulting in a smaller thickness of the partition in Yan 7 and Yan 8.The plane heterogeneity is mainly manifested in the difference of porosity and permeability in the plane distribution.The porosity and permeability of the favorable sedimentary facies in the distributary channel microfacies and the sand body thickness are gradually higher and higher,and the high-porosity and high-permeability zones mostly coincide,that is,the high-porosity zones are the corresponding high-permeability zones.(5)By analyzing the controlling factors of oil-bearing property of different layers in S191 area of Yanwu oilfield,it is considered that Yan 7 and Yan 8 reservoirs belong to lithologic-structural reservoirs.Lithology plays a certain role in hydrocarbon accumulation at this time.Structures play a controlling role in oil and gas accumulation.Skeleton sand bodies and sedimentary facies are the basis of oil and gas accumulation.Lateral shielding is an important condition for reservoir formation.Edge and bottom water have a certain influence on reservoir.On the whole,structure plays an important role in the accumulation and exploitation of Jurassic reservoirs in the study area. |
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