Sedimentary Facies And Reservoir Characteristics Of Chang8₁Reservoirs Of221Block In Zhenyuan Oil Filed

Zhenyuan oil field is located in the gansu province town ZhenYuan,,the constructed area belongs to the Ordos Basin near Shaanxi slopes southwest. The case of the southwest depositional systems, Triassic by the south source control, and the formation of a clastic-dominated sediments, after seven long lake basin expansion starts to contract, to the three long the lake basin shrink faster, its sedimentary environment from a large area underwater sedimentary evolution of water, until deep lake phase disappears and all the evolution of the deposition of the shallow lake. Jurassic, the overall uplift of the basin, the lack of a large area of Zhenbei area Chang2, Chang1strata.In this are,Chang8oil-bearing formation of Yancahng Formation is one of the main oil sequences. facies,sedimentary system,Beause of the limited research on sedimentary facies,sedimentary system,sandbody distribution and hydrocarbon accumulation,the deep cognizance of oil accumulation was restricted,and no more significant breakthrough was taken.In view of the above problems,on the basis of principles of modern sedimentology,using varied analysis and test,this article studies the stratum,sedimentary source,type and characteristics of sedimentary facies,sedimentary facies distribution.By methods of maker beds、Rock mineralogical method、Combination of profile structures and electrical measuring curve characteristics analogy, sedimentary cycles and stratigraphic thickness, And to learn from their predecessors division plan of Yanchang Formation, according to the principle of sedimentology to Chang81internal delamination, The sedimentary cycles combined with GR、SP、AC and so on well logs, Analysis the cyclicity curve form, amplitude and argillaceous interlayer distribution characteristics. Comprehensive analysis of lithology and electric logging curve characteristics research,Chang81intervals will divide into three Small layer. Chang811thickness range of6-15m,, the combination of electrical characteristics of the high GR high AC and low resistance; Chang812thickness range of11-20m,flag layer to the bottom of mudstone or silty mudstone interlayer, the combination of electrical characteristics of the high GR high AC and low resistance; Chang813thickness range of11-20m,sandstone generally poorly developed in this paragraph,flag layer to the bottom of the development of mudstone or silty mudstone interlayer, the combination of electrical characteristics of the high GR high AC and low resistance. Through the vertical and horizontal section in the studied area even the well profile three small layer thickness difference is not big, formation and lesser, topography is smooth.Yancahng Formation is mainly composed of terrigenous clastic rocks,multiple types of rocks, Particle separation is better, mainly for subangular, the sorting medium-better, Intergranular contact way to linear and way of point-line contact as the main contact, particles support accounts for absolute advantage, maturity structure is better. Sedimentary structure commonly bedding structure with horizontal bedding、parallel to bedding、wavy bedding, tabular cross-bedding, trough cross-bedding、ripple cross-bedding and scour surfaces constructed、penecontemporaneous deformation structures and biogenic structures.According to sedimentary facies marks and combined with the regional sedimentary background, the research area is located in the southwestern margin of Ordos, reference the former data、logging and logging data,integrated application of sedimentary rock characteristics、sedimentary structure、log facies characteristics for the identification and classification of sedimentary facies, In identify the study area development braided river delta sedimentary system, mainly developed braided river delta front subfacies. Through the thickness of sand body and sand/ratio statistics,use the superiority of the compilation method and finally compiled flat facies and sand bodies isopach map about Chang81in Yanchang Formation of221block in Zhenyuan oil filed, Comprehensive analysis concluded that the study area as a whole in the underwater deposits, Mainly developed braided river delta front underwater distributary channel, bay between distributary,estuary dam microfacies.Detailed introduction for Chang81、Chang812microfacies sedimentary facies belt and distribution characteristics of sand body in the plane, development of sand body is completely controlled by sedimentary facies belt distribution,was the south west-north east to banded distribution. From the point of plane, small layer sand body in south west-north east to distribution. Chang812small layer of sand on the whole are easy to grow, On the plane a major development in south west-north east to banding distribution of sand body, for the underwater distributary channel sand body. Mainly developed of delta front subfacies including microfacies that underwater distributary channel, mouth bar and nderwater distributary channel side edge etc. Sand body thickness from2m-18m in genera, the most can reach17.3m thick. Chang812small layer sand body development is similar to Chang811, On the plane a major development in south west-north east to banding distribution of sand body, for the underwater distributary channel sand body.But no Chang812development well, Sand body thickness is not big, generally between2m-10m,the thickness is8.9m, In single sand body thickness is very thin.The studied area chang81reservoir sandstone predominantly fine sandstone, sandstone in small amounts. Rock types in the gray-ight sage green、brown gray fine-grained feldspar lithic sandstone and lithic feldspar sandstone, containing a small amount of feldspar sandstone; Cementation type is pore type; Pore combination is given priority to with solution pores-intergranular pores; Pore structure In general belong to the pore throat. Combining with the research area of each small layer reservoir physical property analysis of test data, chang81oil-bearing formation is a Poor reservoir property, porosity is mainly for the middle-low hole, permeability is mainly for the low permeability reservoir. On the whole, the research area has the characteristics of Medium-low hole and low permeability.Systemly studied petrologic characteristics, physical properties, pore types, pore textures of reservoir sand, and diagenesis which affect reservoir, According to the physical parameters and pore structure characteristics and reservoir static and dynamic data of the study area, reservoir sands of the study area is divided into four categories, the types of Ⅰ and Ⅱ.reservoir have good reservoir flow capacity, others are poor, summarize that the types of Ⅱ and Ⅲreservoir are the main reservoir of Yanchang Formation in the studied area.According to analysis of oil-bearing structures,sedimentary facies,diagenetic facies,chang81reservoir is lithology sandstone oil,which is controlled by the tectonism and thickness of sand weekly. Underwater distributary channel, is the basic elements that controlling oil,on the basis,diagenesis play a key role on the control of enrichment of oil reservoir.