The Study On Effective Pore-throat Threshold Of Reservoirs In The 3th Member Of The Gaotaizi Reservoir In Qijia Area

Qi Jia area that is one of the main source layer of Qingshan group is located in west of Qi Jia-Gu Long sag in Changyuan of Daqing,the 3th member of the Gaotaizi reservoir is a set of dense silty and sandstone.The 3th member of the Gaotaizi reservoir is buried deep,and the layer is subjected to strong diagenetic transformation in later period.In the past,there are many researches on the pore structure of the reservoir in he 3th member of the Gaotaizi reservoir in the Qijia area,but more focus on the control of the pore structure of the reservoir,while there are few studies on the accumulation characteristics of the tight oil in the reservoir.In this paper,by using the combination of the theory of injection balance and experimental method,the pore-throat threshold of tight oil filling in the 3th member of the Gaotaizi reservoir of Qijia area is determined,which is of great significance to quantitatively evaluate the reservoir characteristics.Through the methods of core observation,pholos identification,scanning electron microscope and so on,this paper studies the pore structure and types of conventional pores,throats,cracks and nano-micron,and determines the petrological characteristics,structural characteristics,pore types,throat types and types of fractures in the research area.According to the actual geological condition of the research area,the theory of charing mechanical equilibrium is used to analyze dynamics of tight oil in the vicinity of the source storage interface and inside of reservoir in the 3th member of the Gaotaizi reservoir in Qijia area.According to the theory of mechanics balance,the model of the throat threshold for the tight oil in the reservoir near the source reservoir and inside the reservoirs is established.Based on the theory of mechanical equilibrium,the model of the throat threshold of the tight oil in the reservoir near the source reservoir and the inner reservoirs of the 3th member of the Gaotaizi reservoir oil-discharge model is established.According to the actual reservoir parameters in the study area,the throat threshold of the tight oil in the reservoir near the source of the 3th member of the Gaotaizi reservoir in the Qijia region is 22.5nm and 33.58 nm respectively.According to the geological characteristics of the research area,and combining with the actual coring samples in the area,the experimental samples of the Well oil-bearing sections in the coring wells were screened,and the samples were observed with the environmental scanning electron microscope.In this paper,the intergranular pores in tight sandstone and the pore size of tight sandstone in the oil-bearing zone near the reservoir are selected separately in the reservoirs.Combined with energy spectrum detection,the lower throat limits of tight oil charging pore in the vicinity of source storage interface and inside of reservoir are respectively analyzed and determined respectively between 40~50nm and 50~60nm.