EXPERIMENTAL RESEARCH ON THE PLATE MODELS FOR IMPROVING OIL RECOVERY OF RESTORED WATER FLOODING AFTER POLYMER FLOODING

Two different treatments for improving oil recovery after polymer flooding have been studied with the laboratory physical modeling.Moreover effects of models with different permeability contrasts have been considered on the technology of polymer reutilization.Then recognition of the polymer reutilization and effects has been acquired after polymer flooding.Research shows that in the treatment of polymer flooding-water flooding-in-depth profile control-active water flooding,severe fingering will be produced for water mobility higher than that of polymer solution when water flooding has been restored after polymer flooding,then the sweep efficiency of water flooding has been greatly decreased.At the same time,water bulk will dilute the in-depth profile control agent to great extent,which erodes the strength of the in-depth profile control agent,making the worse effect of profile control.In the treatment of polymer flooding-water flooding-flocculating and fixing polymer-in-depth profile control-active water flooding,the flocculates in-site polymer diluted by water flooding,which plug high permeability zones with the floc unit.The following injected polymer-fixed agent will penetrate into the secondary high permeability zone,mix with polymer solution of high concentration and produce cross-linking systems which are excellent in in-depth profile control and oil displacement.It has been testified that in plate model experiments of three different permeability contrasts,the polymer-flocculated and polymer-fixed technology is of long valid period,high strength of the floc unit and cross-linking system,the low cost,high oil recovery and utilizing extent of existing polymer in porous media which makes good foundation for succeeding in-depth profile control and active water flooding.