Evaluation and utilization of nano-micron polymer plug for heterogeneous carbonate reservoir with thief zones

Abstract

Thief zones are highly permeable zones in oil reservoirs which affect the performance greatly during water flooding.The most effective way to prevent the invalid circle of thief layer is the injection of high-concentration polymer slugs. In this paper, the plugging effect of nano-micron polymer flooding on the thief zone is studied by experimental and theoretical analysis.The changes of water content and flow resistance were analyzed under different conditions. The result shows that the model presented here has good agreement with the experimental results. The displacement effect is the best when the thief zone is located on the upper part of the reservoir. And the water content will decrease with the increase of flow resistance after nano-micron polymer injection. Besides, the higher the polymer concentration, the more obvious the decrease of water content, and more effective the plugging. This study has provided a quick and reasonable guide in the later adjustment of water flooding development of carbonate reservoirs with thief layers.