Study On Interpretation Standard For Effective Thickness Of CO₂ Flooding In Fuyang Reservoir Of Shu101 Block In Yushulin Oilfield

Shu101 Block of Yushulin Oilfield in the study area is located in the northeast slope of Sanzhao Sag in the north of Songliao Basin.It belongs to the east of Xujiaweizi Fault Depression,adjacent to Wangjiatun Structure in the west,Shangjia Nose Structure in the East and Xingshan South Structure Zone in the southwest.The main target layers are the ultra-low permeability Fuyu and Yangdachengzi reservoirs in the third and fourth Quanquan Formations,with high crude oil viscosity.So far,a considerable part of the reserves that have been put into development are in a state of inefficiency.Because of the poor physical property of reservoir,it belongs to ultra-low permeability reservoir,and the high viscosity of crude oil,the obvious effect can be seen in the early stage of water flooding,and after a period of time,the difficulty of water injection and other problems will become worse.Gas flooding,especially CO₂driving technology,can significantly reduce the viscosity of crude oil and effectively develop low permeability reservoirs.However,the logging physical and electrical criteria established in the early stage of development can not fully adapt to the interpretation of CO₂ driving reservoirs.It is necessary to redevelop logging interpretation research for CO₂ driving reservoirs,and determine the physical and electrical standards and fine interpretation model of reservoir parameters that are suitable for its development means.It is of great significance for guiding oil and gas development to determine reservoir physical property boundaries suitable for CO₂ driving and to establish interpretation criteria for effective thickness.Firstly,the logging data are used to determine the"four properties"of reservoirs suitable for CO₂ driving,and a good relationship between lithology,physical properties and oil-bearing property of Shu101 Fuyang reservoir is determined.That is,the coarser the lithology,the better the sorting,the larger the porosity and permeability,the greater the acoustic time difference;and the higher the oil saturation,the greater the resistivity.When core lithology is finer,sorting is worse,physical property is worse and oil-bearing grade is lower,the abnormal amplitude of spontaneous potential is smaller,the natural gamma is bigger,and the acoustic time difference is smaller.Then,the interpretation chart of effective porosity and permeability is established by using core,well logging and mercury injection data of coring wells.Finally,the effective reservoir thickness criteria for CO₂ driving are determined by using oil testing method,pressure gradient method,laboratory analysis experiment and field data:effective porosity??9.0%?,air permeability(?0.1*10^-3?m²),oil-bearing property and lithology are above oil-immersed siltstone grade.