Study On Seepage Law Of Microspheres Profile Controlling And Flooding System In Heavy Oil Cold Production

Heavy oil occupies a large proportion in fossil energy.Due to the characteristics of high viscosity and high density,the sweep effect of conventional water flooding is poor.The intra-layer contradiction and interlayer contradiction are more prominent in the process of water drive development of heavy oil reservoir.,due to traditional profile control agents normally act on the near wellhead zone with poor migration ability and limited profile control effect,polymer microsphere deep profile controlling and flooding,as a new technology to improve the development performance of heterogeneous reservoirs,has attracted extensive attention in recent years.In the process of oilfield development,the long-term erosion of the reservoir by water flooding aggravated the heterogeneity of the reservoir,and the formation of water-dominant channels in the high-permeability zone will lead to water channeling,which seriously affected oilfield's development effect.Based on the systematic study of the physicochemical properties of the polymer microsphere dispersion system,combined with theory and laboratory core experiments,this paper has completed the following work around the seepage characteristics of the microsphere control and displacement system and its control and displacement mechanism:Based on the conventional characterization methods of polymer materials,the physical and chemical properties of the polymer microsphere dispersion system were characterized and evaluated from the aspects of the morphology,particle size and distribution,hydration and expansion properties and its influencing factors,rheological properties and viscoelasticity.The results show that the polymer microspheres have good roundness,their particle size distribution basically conforms to the normal distribution,and their hydration and expansion capacity is affected by hydration time,temperature and salinity.The longer the hydration time,the higher the temperature and the lower the salinity,the better the hydration and expansion effect of the polymer microspheres.The microsphere dispersion system has certain shear resistance and good viscoelasticity.Carried out core seepage experiments to characterize the migration and blocking of the microspheres during the seepage process of the microspheres profile controlling and flooding system through pressure changes.The injectability,blocking property,migrationand blocking characteristics of the microspheres profile controlling and flooding system,and the effect of liquid flow reversal were characterized and evaluated.The results showed that the microspheres profile controlling and flooding system in the core to "transport-blocking-breakthrough-transport" manner percolation,whose injection pressure is presented to the wave rising.The liquid flow reversal effect is affected by thepermeability level difference.The smaller the permeability level difference,the better the liquid flow reversal effect.According to the characteristics of heavy oil reservoir,using microscopic visualization model,whole core CT scan and MRI scan technology,combined with core experiment results and micro force analysis,the microscopic seepage mechanism of the microspheres profile controlling and flooding system was studied.The microsphere control and flooding system has selective blocking properties,mainly blocking throats with relatively large pores,which can effectively improve the sweeping efficiency.The microscopic seepage laws mainly include rock wall adsorption,blocking of pores,bridging and blocking of pores,and negative pressure oil displacement generated when deformation passes through the pores.Through numerical simulation,the seepage characteristics of the microspheres profile controlling and flooding system in the reservoir and the formation pressure change during the control and displacement process are described.Microspheres and implantation parameters flooding system is preferred,a comprehensive analysis is preferably the optimum injection amount,injection timing of implant concentration and transferrin.The best injection plan is to inject 0.5PV the microsphere control and flooding system,and the injection concentration is3000mg/L,the injection was transferred when the comprehensive moisture content was 80%,These conclusions provide theoretical basis and data support for field application.