Determination Of Reasonable Pressure Gradient At Different Stages Of Polymer Flooding In South Seven Area

As the oilfield waterflood development gradually coming to an end,polymer flooding has become the main measure to increase oil production.However,because of the influence ofthe reservoir physical parameters,geological structure and other factors,it is necessary to consider comprehensively,and to configure the reasonable production process parameters,in order to realize the rational development of oil fields,increase production of oil,and then optimize the development effect.The geological structure in the South seven area of Daqing is complex,and there is a big difference between new and old oil reservoir.At the same time,the effect of some reservoirs is poor,with the influence of fault development,which make it difficult to realize the reasonable development of different stages of polymer flooding.Injection production pressure gradient is closely related to the effect of polymer flooding,So how to build a reasonable polymer flooding pressure gradient is particularly important.Based on the new and old wells and well logging interpretation data in South seven area,weuse Petrel to establish the geological model tofine reservoir description of the South seven reservoir.At the same time,using Petrel modeling results to come true numerical simulation in the Eclipse software.Single factor analysis and grey correlation analysis method were used to screen the factors affecting formation pressure.With the actual field comparison and establishing the inflow dynamic model of simple polymer flooding well,the reasonable flow pressure limit is determined.Finally,combined with the factors that affect the pressure gradient of polymer flooding and the flow pressure limited,the numerical simulation of the practical scheme is optimized.Then reasonable pressure gradient limit of polymer flooding is determined at different stages and realize the optimization of injection-production plan.What is more,the influence of reasonable pressure gradient on recovery efficiency and sweep coefficient is analyzed.Results show that the main factors affecting the formation pressure in the South seven areas are injection intensity,liquid production intensity,injection concentration.In the different stages of polymer flooding,the flow pressure limits in the South seven areas are not the same.The flow pressure limit in the early stage of polymer flooding in southern seven area is 4.7~7.5MPa,the decline period is 2.5~4.5MPa,and the recovery period is 4~5.7MPa.The reasonable pressure gradient limit is between 0.076~0.094 MPa/m,the decline period is between 0.091~0.107MPa/m,and the recovery period is between 0.095~0.116MPa/m.The recovery coefficient and sweep coefficient increase with the increase of pressure gradient,and the sweep coefficient is smaller than the pressure gradient from the middle to the late stage.