| For reservoir with strong heterogeneity,there are serious conflicts among layers in the process of water injection.The injected water flows into the high permeability layer,the water cut of the production well rises rapidly,and the oil recovery of low permeability layer is low.Preformed dispersion gels with delayed expansibility and high strength are an effective way to reduce heterogeneity and enhance oil recovery.In this thesis,dispersion gels SIPNG were prepared by inverse emulsion polymerization.After purification and drying,the dispersion gels presented uniform powder,the gels were regular round and spherical,and the particle size was micron.The dispersion gels have good thermal stability,suspension,dispersibility and long-term stability in formation water.It reached the expansion limit in 15 days under the formation conditions and showed good retardation of expansion.The dispersion gels have high mechanical strength,and maintain high strength after aging under the formation conditions.The gels have good viscoelasticity.The injectivity of SIPNG gels in core was studied by core displacement experiments.When the permeability was too low,the gels could not be injected into the core.Under suitable permeability conditions,the gels has good injectivity.When the permeability is too high,the gels cannot plug the pores effectively.The higher the injection rate,the better the injection performance of the gels and the lower the plugging property of pore throat.The higher the concentration of the system,the more difficult the gels are to be injected into core.Under the appropriate penneability conditions,the injection performance of the dispersion gels can be slightly reduced with the increase of strength,but the plugging efficiency can be improved.The heterogeneous control ability of dispersion gels was studied by paralleled core displacement experiment.The dispersion gels had selective injection and could enter cores with higher permeability.Dispersion gels have a good ability to improve the profile.The stronger the heterogeneity is,the weaker the ability of dispersion gels are to improve the profile.The larger the injection volume of dispersion gel is,the greater the reduction of heterogeneity will be.Under the condition of heterogeneity,the injectivity of dispersion gels can effectively increase the recovery rate of low permeability.With the enhancement of heterogeneity,the increase rate of oil displacement efficiency of low permeability core shows a trend of first increase and then decrease.When the penneability contrast is 10.2,the increase rate of recovery rate reaches the peak.By microscopic experiment and core displacement experiment,the migration and retention rules of dispersion gels in pores were studied.Capture blocking;Coincidence blocking;Bridge blocking;Elastic blocking and remigration;Depression and release.The fluid pulling force detennines whether the dispersion gels retained on the pore surface can remigrate.Through the combination of nuclear magnetic resonance experiment,core wettability experiment and core displacement experiment,the profile control mechanism of dispersion gels was summarized:selectively entering the hypertonic zone,increasing the flow resistance of liquid flow in its pores,leading to liquid flow direction change and expanding the sweep efficiency of injection water;Sedimentation-release,elastic blocking-breakthrough migration reciprocate alternately to achieve deep profile control.The oil displacement mechanism of dispersion gels are:Elastic deformation enters the pore,and the oil film on the pore surface is peeled off;Enter the pores with dead ends and "squeeze" the remaining oil out;The negative pressure formed by the elastic breakthrough "sucks" the remaining oil from the adjacent pores together;The dispersion gels can be retained on the pore surface to improve the wettability of rock.The study of this paper has certain guiding significance for the numerical simulation and field application of SIPNG dispersion gel for deep profile control. |
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