Experimental Study On The Hierarchical Combination Deep Profile Control Technique

The depth profile control technique of hierarchical combination is making a hierarchy of the profile control agent based on the difference of reservoir permeability.The continuous phase polymer gel is used as a first order profile control agent to block the big pore channel in the near-bore area.The dispersed phase particle plugging agent is used as the two stage profile control agent to change the deep fluid diversion in the further bore zones.The fast-dissolved polymer is used as the third stage oil displacement agent to reclaim the remaining oil in the medium permeability layer.It is necessary to optimize the sequence and size of each slug combination so that the multistage profile control slug can play a synergistic effect.In this paper,experimental studies on viscosity,viscoelasticity,seepage characteristics,transport and plugging ability of various profile control?displacement?agents and the steering effect of deep liquid flow have been carried out through instrumental analysis,chemical analysis and physical stimulation techniques,guided by physical chemistry,polymer materials and reservoir engineering theory,based on the actual geological characteristics and fluid properties of reservoirs in Bohai S oilfield.The result show that when the content of the polymer in the gel is similar to that of the chromium ion,the gelation is fast at high temperature.After 1.5 hour,the crosslinking reaction has been fully occurred.In order to avoid polymer gel entering the low permeable layer,it is required that the initial viscosity of the gel is low and the strength of the gel is high after the gel formation."1#polymer+8#crosslinker","5#polymer+8#crosslinker","16#polymer+15#crosslinker" and "18#polymer+20#crosslinker" polymer gel basically meet the above conditions,using them as the first class profile control slug.The sealing performance of polymer microspheres is almost not affected by the shear effect.With the prolongation of the hydration time,the microspheres can absorb water and expand,so it can penetrate deep in the deep pores of the reservoir.Select "11#polymer microsphere" as the two stage profile control slug.The fast-disiolved polymer can be completely ripened in 25min³0min,especially suitable for offshore oilfield platform conditions.After the comprehensive evaluation,the "36#fast-dissolved polymer" was selected as the three stage profile control and flooding plug."Cr³⁺polymer gel?first low concentration,high concentration?+polymer microsphere and fast-dissolved polymer composite system+fast-dissolved polymer" three stage displacement slug eventually increases recovery rate of22.1%,which is far better than "polymer gel+polymer microsphere" two level profile control slug or "polymer gel" first level profile control slug.