Study On Microscopic Residual Oil Distribution Characteristics Of First Type Tract In Chaoyanggou Oilfield

The low-permeability reservoirs in Daqing entered the development stage.Due to the lack of understanding of the pore structure of low-permeability reservoirs,the fluid seepage characteristics in the pores are unclear,there are problems such as high starting pressure,invalid water injection cycle,and severe Jiamin effect,the recovery rate of water flooding is very low,and a large amount of crude oil remains in the pores and cannot be well utilized.At present,the understanding of the microscopic oil displacement mechanism for the enhanced oil recovery technology is not perfect.Therefore,it is necessary to take certain measures to conduct depth research on the pore structure of the oil reservoir,thereby improving the oil displacement effect of the low permeability oil reservoir and obtaining the remaining oil displacement mechanism.In this paper,a large number of indoor lithographic glass flooding experiments about changeing displacement methods were conducted,The low-permeability reservoirs are subdivided into three(low,medium,and high)permeability grades to allow targeted study the producing condition and the evolution process of cluster residual oil,film residual oil,droplet residual oil,columnar residual oil and dead-end residual oil in different water-containing stages,and the displacement effects of various measures under different pore conditions,the effective way to displace all kinds of residual oil is obtained.The experimental results show that the clustered residual oil accounts for the largest proportion of five types in water flooding.By comparison,on the basis of conventional water flooding,changing the mobility of displacement fluid has the largest drop in the saturation of the residual oil and the largest increase in oil displacement efficiency,followed by changing the direction of displacement and periodic injection,changing the displacement pressure has the least drop in the remaining oil saturation and the least increase in oil displacement efficiency.Changing the direction of the displacement mainly activates the cluster residual oil and columnar residual oil;periodic injection mainly activates the cluster residual oil and columnar residual oil;increasing the displacement pressure difference mainly activates the cluster residual oil and oil droplet residual oil;reducing the mobility of displacement fluid can effectively reduce the saturation of five remaining oils.At the same time,fluorescence microscopy and CT scanning were used to study the distribution of remaining oil in different water-bearing stages.Compared with the conventional water flooding results of the lithographic glass model,the change regulation of residual oil is generally consistent.