Characteristics And Evaluation Of Tight Sandstone Reservoir In Qing 1 Member Of Qian 178-Gu 46 Well Block

The first member of Qingshankou Formation in Qian 178-Gu 46 Well Block is the main tight sandstone oil reservoir in Songliao Basin.The favorable areas of the tight sandstone reservoir in the study area are unknown with large thickness and wide distribution.In order to further clarify the characteristics of the tight sandstone reservoir and put forth effective reservoir evaluation method,this paper evaluates the formation characteristics,based on high-pressure mercury injection experiments,Scanning Electron Microscopy?SEM?experiments and triaxial mechanical test experiments and carries out comprehensive evaluation of the formation from the aspects of lithology,physical property,microscopic pore structure,electrical property,oil bearing and brittleness,on the basis of further study of the logging data and core sample experimental data.And a reservoir evaluation and favorable area comprehensive prediction method is formed,and the favorable area is finally determined.The characteristics of reservoir are studied from the aspects of lithology,physical properties,microscopic pore structure and the limitations physical properties of the oil-bearing formation.The porosity and permeability of the tight sandstone oil reservoirs in the study area are less than 10%and 0.1×10^-3?m² respectively.The main pore types are intergranular micro-nano pores and the reservoir of study area belongs to extremely tight and low-porosity reservoirs.Tight sandstone reservoirs have multiple fractal characteristics,and the number of fractal intervals and the comprehensive fractal dimension can be used as the criteria for the evaluation and classification of reservoir physical properties.Type I reservoirs have two fractal intervals and the fractal dimension is generally less than 2.44,with permeability and porosity are greater than 0.1×10^-3?m²and 8%,respectively.And the physical properties are good.Type II reservoirs have three fractal intervals and the fractal dimension is between 2.44and 2.5,with the permeability between 0.01×10^-3?m² and 0.1×10^-3?m² and the porosity between 5%and 8%respectively.Type III reservoirs have 4 fractal intervals with fractal dimension ranging from 2.5 to 2.9 and the physical properties is poor.Type IV reservoirs have five fractal intervals with fractal dimension generally greater than 2.9 and the physical properties are extremely poor.About 70%siltstones in the study area have good oil bearing and siltstones,so the Siltstone is the main oil layer of research area.The research of the lithology,electrical property and oil bearing property of the study area shows that the intersection figure between acoustic time and gamma value can significantly predict the Siltstone reservoir.The intersection figure between Acoustic time and deep lateral resistivity can be used to predict the oil-bearing occurrence in Siltstone reservoir and based on which,the prediction standard of the oil content characteristics are established.Core sample shows oil immersed or oil spot for type?reservoir,and logging identification standards is that AC>221us/m and RILD>-1.37AC+327.88?·m.Core sample shows fluorescent or no fluorescent for type III reservoir,and the logging identification standards is that AC<215us/m and RILD<-1.37AC+327.88?·m.Core sample shows oil stains or fluorescence for type?reservoir,logging identification standards is between the above two type.The calculation of dynamic mechanical parameters and brittleness index based on well log data is an effective method to evaluate the brittleness of tight sandstone reservoirs.When the brittleness index is more than 50%,it is Type I Reservoir and when the brittleness index is between25%and 50%,it is Type II reservoirs.The lithology,physical property,microscopic pore structure,electrical property,oil bearing and brittleness of reservoir can effectively evaluate and classify tight sandstone reservoirs and can also effectively predict favorable areas of reservoirs.