Injection profile inversion timing judgment model for polymer flooding and its theoretical validation

In the background of low oil price, polymer flooding plays a crucial role in offshore development of high-permeability and viscous oil reservoirs. However, during the whole flooding process, profile inversion occurred frequently and could lead to inefficient or low efficient circulation of polymer. Knowing the timing of profile inversion could implement the multi-plug mobility adjustment technology duly, it can effectively expand the sweep volume. At present, the mechanical control factors and influence laws of the profile inversion timing are still unclear, and the suitable mathematical model for judging the timing of profile inversion is also missing. Therefore, on basis of two-layer one dimensional flow model of heterogeneous reservoir, the flow rate distribution model and profile inversion timing judging model are established respectively. These two models are verified by fitting changing parameters of resistance factor using polymer core flooding data, and the influence rules of polymer profile inversion timing are also discussed in this paper. The results show that profile inversion timing is affected by parameters c and d on high permeable layer and parameter b on low permeable layer, which parameters b and d have negative correlation and parameter c has positive correlation with the timing. Based on the established profile inversion timing judgment model and combined with polymer core flooding relative flow ratio data, we can obtain the changing parameter of resistance factor which provide a new quantitative method to evaluate polymer system, predict flooding effect and judge implement time of multi-plug injection technology. (paper)