Sedimentary Characteristics And Reservoir Evaluation Of Triassic Yanchang Formation Chang 6 Oil-Bearing Strata In Shangzhenzi Area,Ordos Basin

Sedimentary microfacies and reservoir characteristics are the key factors controlling oil and gas accumulation and migration.Sedimentary characteristics and reservoir evaluation studies are of great significance for the exploration and development of turbidite reservoirs.This paper studies the Chang 6 oil-bearing formation of the Yanchang Formation in the Shangzhenzi area of the Huangling exploration area.Based on structural geology,sedimentology,reservoir geology,petrology and logging geology,conventional physical property analysis and logging data are used.Logging data,multiple assays,stratigraphic division and sedimentation,sedimentary microfacies,sand body distribution,lithology analysis,pore structure,reservoir physical properties,sensitivity and reservoir seepage characteristics,etc.,to establish comprehensive reservoir evaluation Standards,evaluation of reservoirs in this area.According to sedimentary composition,sedimentary microfacies,core description,particle size analysis,observation of cast flakes,single well logging phase analysis and comparison of continuous well profiles,it is considered that the Chang 6 oil-bearing formation of the Yanchang Formation in the Shangzhenzi area is mainly due to the delta front water landslide.The turbidite is the main type,and the microfacies such as the turbidite channel,the turbidite channel,and the side edge of the channel are developed.The turbidite channel is a favorable reservoir facies belt.Through the observation of cast thin section,heavy mineral report,physical property test report and core data analysis,it is concluded that the rock type of Chang 6 reservoir is mainly light gray and gray feldspar sandstone,and the debris components are mainly feldspar and quartz.The line particles are mainly in line contact and point-line contact,and the local contact point is contact;the interstitial is mainly mica,calcite,chlorite and illite,of which calcite accounts for the largest proportion,and a small amount of iron dolomite and silicon Quality;the cementation type is mainly composed of pore cementation and continuous crystal cementation.The pore types are mainly intergranular pores and various dissolved pores,and a small number of fracture pores,the average pore throat diameter is0.65?m,the reservoir pore structure is complex,the pore throat diameter is small,the permeability is small,and the relative sorting coefficient is small.Low porosity and low permeability reservoir.According to the physical property data and log interpretation analysis,the average porosity of Chang 6 reservoir is 8.01%,and the permeability is 0.41×10^-3?m².This area mainly undergoes three diagenesis actions:compaction,cementation and dissolution.Zhongchengyan A period;Chang 6 reservoir is generally weak,sensitive,moderately strong-weak water sensitivity,weak salt sensitivity,weak-moderate weak alkali sensitivity and acid sensitivity is improved.According to the research results of sedimentary facies,sand body thickness,reservoir porosity and permeability,and interlayer distribution,the classification criteria for the reservoir level of the Chang 6 oil-bearing formation are established,and the reservoirs in this area are divided into four categories,each small layer.The reservoir types are mainly type II and III reservoirs,and the distribution of type I reservoirs is small.