Reservoir Evaluation Of Fuyu Oil Layer In Sanzhao Depression

The main characteristics of the Fuyu oil layers in the Sanzhao Depression are of the confluence area of the provenance,no clear knowledge of the distribution of the sandstones,complex pore structure,relatively poor reservoir physical properties,and strong heterogeneity.It is hard to develop due to complex oil and water distributing relationship,which seriously restrict further exploration and development.In order to find out the distributing rule of the oil and water,provide available geological evidences for further exploration and development,it is necessary to carry out comprehensively evaluate upon the reservoir.The main understandings are as follows:(1)The structural contour map of the top of Fuyu oil layer shows that the study area was characterized by both high in north and south,low in the middle,steep west and low-dip east,and overall showing the tectonic framework is of one saddle,three nose structure and two depression.The result of research shows that Fuyu oil layer developed NNW and NE dimension rifts and the variously sized fault block formed by the rifts cut each other.(2)On the basis of core observation,particle size analysis,and log facies analysis,together with regional geological background data,it was concluded that the sedimentary microfacies type is shallow water delta depositional system,including distributary channel microfacies,Natural levees microfacies,crevasse-splays microfacies,split between bay microfacies,underwater distributary channel microfacies,state of sandstone table microfacies,and shallow lake mud,etc.On the basis of the single well of sedimentary microfacies research,quantitative identification of sedimentary microfacies of the study area using the fuzzy C-means clustering.The combination of sedimentary microfacies distribution pattern drawn each destination microfacies plane maps.Compared with conventional method,this method we mentioned here can make full use of all log information,with a relatively higher recognition accuracy.(3)The study area of Fuyu reservoir is in the source junction and sandstone distribution pattern is complex.hrough the analysis of the sandstone profile,geometry,contact relationship,under the control of the microfacies,draw the layout of the plane of the target layer of sandstone.In vertical,there are poor connectivity between each well with the lenticular sandstone.In the plane,the sandstone of each layers is banded or dendritic distribution.Reservoir sandstone in general in order to divert the river sandstone,underwater distributary channel,sandstone sheet,sandstone,which have poor connectivity and strong heterogeneity and analysis of reservoir heterogeneity on oil recovery.(4)The rock types of reservoir in our study area are mainly feldspar-debris sandstones.Mercury-injection tests have shown that the pore structure of the reservoir is mainly small to medium pore throat type,the main pore types are as follows:dissolution pore,intergranular pore,intergranular-microporous and microporous,with a porosity value range between 6?15%,averaging 10.6%;and a permeability value range between 0.02?10-3?m2,averaging 0.9×10-3?m2,therefore,the reservoir belongs to low porosity and ultra-low permeability one.(5)On the basis of study of four-propertiy relationships,using testing and logging data,the identification plate for the oil-water layer of the Fuyu oil layer has been established.The effective thickness of the lower limit of the physical properties standard has been established with the method of oil production test and oil occurrence,that is the porosity of 9.0 percent and the air permeability is 0.1 ×10-3?m2.Through comparing,the deep lateral resistivity and acoustic slowness curves were selected to establish the effective thickness electrical low limit standards.(6)The reservoir type of the Fuyu oil layer are mostly lithologic and structural-lithologic reservoirs with the source-reservoir-cap assemblage of oil generation formations in the above and reservoirs below.In vertical,there are three main water distribution forms:pure oil,oil in the upper part and water in the lower part,and up and down oil,the middle for the water.Oil-water interfaces for the Fuyu oil beds in Sanzhao area are not unified in different geological structures and areas,which present multiple oil and water combinations.Under the integrated influence of faults,lithologies and position of structure,the accumulation degree of oil are quite different in deferent fault blocks,showing that oil in horst blocks and fault zones are relatively enriched.Oil distributes in sheet shape in F I,and stray distribution in F ?.(7)Faults are main controlling factors,which control the oil and gas migration and their accumulation,and lithological change is a key factor in the formation of lithologic oil and gas reservoirs;effective matching among faults,lithology and structure is an important condition for hydrocarbon accumulation.Sedimentation plays the innate role in controlling the development of reservoir and diagenesis is the root cause making the reservoir low porosity and permeability.In the macroscopic scale,the sedimentation controls the scale of sandstones and their spatial distribution.In the microscopic scale,the sedimentation determines the characteristics of the rock particle size,interstitial material and the rock structure and controls the primary reservoir porosity and permeability.(8)Diagenesis of carbonate cementation,siliceous iron muddy filling dissolution play a constructive role in the study of reservoir.Compaction and metasomatism makes the reservoir properties variation.The main types of reservoirs in the study area are ?2,?1,?2,?,and ?2.Based on the effective reservoir thickness distribution,the scope of favorable area has been delineated by testing data.From affecting reservoir quality,comprehensive evaluation the reservoir of Fuyu oil layers in the Sanzhao Depression by K-means algorithm using six kinds parameters,including sandstone thickness stratum thickness effective thickness,porosity,permeability,sedimentary facies.The reservoir is divided into three type favorable areas(?,?,?)and the study area mainly developed in class ? and ?,class ? favorable areas in the area scattered development.