Study and Application on Reutilization Technology of Residual Polymer After Polymer Flooding

Abstract

There is a large amount of residual polymer existing in the forms of solution, adsorption, and entrapment in formation after polymer flooding. Then the water cut ascends quickly along high permeable channels when displacing water. In order to improve sweep efficiency of water flooding and use residual polymer effectively in formation, the reutilization technology of residual polymer in formation is proposed and developed. When the reutilization agents (including a flocculating agent and fixed agent) are injected, they react with residual polymer to form floc units and cross-linking units that could block high permeability channels and control cross flow. As a result, the sweep efficiency of water flooding and oil recovery could be enhanced. In this article, the optimized flocculating agent is selected through suspension experiments and the fixed effect for polymer is studied in sand pack core models, and the residual resistance factor is used as the evaluation criterion. The experiments show that solid particles can be used as a flocculating agent and the optimal flocculating agent is stabilized sodium clay; the cross-linking agents can be used as a fixed agent and the optimal fixed agent is selected depending on formation temperature and the salinity. This technology has been successfully applied in Henan oilfield, Shengli oilfield, and Daqing oilfield. The water cut and produced polymer concentration decreases dramatically and oil production increases obviously. This technology, which belongs to quaternary oil recovery technology, is a preferred improved oil recovery technology after polymer flooding and has a broad application prospect.

Keywords:

• application
• improved oil recovery
• polymer flooding
• residual polymer
• reutilization