Study Of The Influence Of ASP Flooding Effect By Stratified Injection In Class ? Reservoirs In Daqing Oilfield

Daqing oilfield has entered into high water cut development stage,the water content in main reservoir is more than 94% and therefore,development of class II reservoirs will be the main direction in the future.In order to identify the development law of heterogeneous reservoirs,heterogeneous core model with three layers has been designed and made.Then oil displacement experiment is carried out.Under the condition of five-point well pattern method,ASP flooding of three layers general injection and stratified injection were carried out successively.Along the main flow direction in the process of displacement,recording the pressure distribution,produced fluid viscosity,interfacial tension changes and changes of oil saturation at every point in three layers,then draw a saturation distribution map.In this way,the best method to enhance the oil recovery efficiency is selected.The research can provide theoretical guidance and experimental basis for field application.The results show that ASP flooding adapts to the class II reservoirs in Daqing oilfield.But general injection method leads to low sweep efficiency because chemical agent mainly migrate along the high permeable layer,the effect in the medium and low permeable layer is not obvious.Recovery rate continues to increase by 28.9% on the basis of water flooding.The ultimate recovery is 50.9%.Stratified injection and production can improve the producing degree effectively in medium and low permeable layers during water flooding stage.When ASP flooding begins,chemical agent can migrate farther in medium and low permeable layers,extending its function time.Therefore,the overall efficiency of the reservoir is greatly improved.Recovery rate continues to increase by 35.18% on the basis of water flooding.The ultimate recovery is 56.45%.Under the two kinds of development methods,comprehensive comparison of the change of chemical agent,reservoir producing degree,residual oil saturation and oil recovery degree.We can know that stratified injection and production is more adapt to develop class II reservoirs in Daqing oilfield.Stratified injection and production makes a higher oil recovery.