Study On Flow Mechanism Of Polymer Microspheres Dispersion System In Fractured Low Permeability Reservoir

At present,the polymer microsphere dispersion system flooding is an effective method to improve the recovery of low permeability reservoirs.With its progressive seepage deep into formation,the exploitation process would witness a satisfied recovery ratio.However,since the scales of cracks in fractured low-permeability reservoirs are very small,below 150 ?m,it remains an unsolved issue whether the polymer microsphere dispersion system is suitable for fractured low-permeability reservoirs and further enhanced oil recovery.As a result,it is urgent to carry out research on the displacement mechanism and seepage law in fractured low-permeability reservoirs to clarify the corresponding ways to enhance oil recovery and futhermore,provide further guidance to the development of the oil field.Thorough investigation were carried out on the status quo of the development of the polymer microsphere dispersion system flooding technology.Further experimental and theoretical studies were conducted on the characteristics of flooding and seepage flow of the polymer microsphere dispersion system in fractured low-permeability reservoirs.1.By controlling the synthesis conditions,we successfully produced the SiO2-PMBAAm-PAM core-shell polymer microspheres.The polymer,made by self-assembly techniques,has a more regular spherical shape and a more concentrated particle size distribution.We first analyzed the apparent morphology,particle size distribution,viscosity,and rheological characteristics of the microspheres.Its excellent performances in swelling properties,viscosity stability,and shear resistance make it possible to selectively enter the pores of different formations.Multi-stage microfiltration membrane experiments and displacement experiments carried on fractured low-permeability cores reveal that,on the one hand,the synthetic polymer microsphere dispersion system can selectively enter the pores of different scales in the matrix pores to improve the displacement effect progessicely;On the one hand,for the case of fractures,it can temporarily block and adjust the flooding process.The polymer microsphere dispersion system is a favorable displacing agent for fractured low-permeability reservoirs and can improve the flooding effect deep into formations to achieve an enhanced oil recovery.2.In addition,the migration properties of the dispersion system in matrix-fracture media were examined on the microscopic visual simulation model.The results demonstrated the role polymer microspheres played in fractured low permeability media during microscopic displacement process.At the same time,we investigated the blocking and displacing mechanisms of the polymer microspheres using the sand packed model containing fractures.The model offered a specific demonstration on the progressive seepage process of polymer microspheres dispersion system and its percolation characteristic in dual medium reservoir.3.Through indoor microtubule experiments and macroscopic flow experiments,we have studied the plugging characteristics and related percolation mechanisms of polymer microsphere dispersion systems in different pore structures.The results,not only revealed the seepage behavior and influencing factors of polymer microsphere dispersion systems,but also illustrated the macroscopic seepage law and seepage characteristics from a macro perspective.4.Based on the experimental research,two mathematical models were established,giving specific demonstrations on the flooding characteristics of polymer microsphere dispersion system as well as its filtration mechanisms in dual medium formation respectively.Further numerical simulations were carried out on a typical reservoir.The results provides substantial reference to the laws that polymer microsphere dispersion systems play in improving the effect of water flooding and what's more,further guidance to the exploitation of fractured low-permeability oil fields.The results of this dissertation provide theoretical and technical support for the development and application of polymer microsphere dispersion system in fractured low-permeability reservoirs as well as its effect on enhanced oil recovery for displacement improvement in deep formation.