Research On The Factors Affecting The Microscopic Oil Displacement Effect Of Polymers In Heavy Oil Reservoirs

Polymer flooding characteristics in Bohai heavy oil reservoir is far lower than the onshore oil displacement effect due to the high viscosity of the crude,serious heterogeneity,reservoir thickness and other factors.Therefore,it is necessary to make a further understanding of polymer flooding mechanism for higher displacement efficiency in heavy oil reservoirs.As a result,we need to study the effect of heterogeneity,injection timing and polymer concentration on the residual oil distribution,mobilization and oil recovery.First of all,three layer simulation heterogeneous etching glass model,1/4 five homogeneous spot well pattern and heterogeneous etching glass model are designed according to the pore structure of heavy oil reservoir in Bohai.Micro displacement experiment of water and polymer flooding is conducted using the etching glass micro model.In the test,we make a thorough inquiry of characteristic parameters such as displacement front,residual oil distribution and oil recovery and in turn demonstrate the reliability of micro etching model.Analyze the microscopic oil displacement mechanism through the research of heterogeneity,injection timing and polymer concentration that affect he flow characteristics and the oil displacement efficiency on heavy oil reservoir.(1)Water-flooding front darts obviously in heavy oil reservoir,which lead to the rapid water breakthrough,seriously affect polymer flooding and subsequent water flooding sweep efficiency and the microscopic displacement efficiency;when it breakthrough,the swept volume increase slowly and more slowly with the more serious heterogeneity.(2)Polymer injection before water break is clearly better than direct injection and injection after it breaking.On the one hand,polymer injection before water channeling can effectively control water channeling flow,and thus enlarge the swept volume,while direct injection resulted in reversal profile limiting the sweep efficiency;on the other hand,it has better ability of microscopic oil displacement efficiency compared to the injection after breaking.(3)Oil displacement efficiency raise rapidly with the increasing of polymer concentration and it is better than injection after breaking,which indicates that it is needed to improve concentration to enhance oil recovery.Using the strong mobility-control polymer solution and selecting the appropriate injection time and the concentration of polymer can effectively improve the heterogeneous heavy oil reservoir with polymer flooding.