Study On Polymer Microspheres Mechanism Of Profile Control And Experiment For Low Permeabiltiy Reservoirs

In the middle and later stages of low permeability reservoir development,high permeability zones are formed due to long-term water injection,and injection water is produced along the high permeability zones to the production wells,forming an ineffective water injection cycle.To solve this problem,an elastic polymer microsphere with pore throat size was developed by inverse microemulsion polymerization.The polymer microspheres have the advantages of water plugging,oil plugging and expanding sweep volume in field application,thus significantly improving oil recovery.However,in field application,the determination of parameters such as particle size,injection concentration,injection volume,injection timing and the most suitable permeability gradient of polymer microspheres is not clear.Therefore,these parameters will be evaluated and studied through laboratory experiments.Firstly,the physical and chemical properties of polymer microspheres were studied to provide basic parameters for displacement experiments.The micro-morphology of polymer microspheres was observed by polarizing microscope;the expansion characteristics of polymer microspheres were quantitatively characterized by laser nanoparticle size analyzer;and the viscosity of polymer microspheres with different concentrations at 60 ? was measured by rheometer.Then,the plugging efficiency and recovery of polymer microspheres at different injection rates were measured by using a single sand filling pipe displacement simulation experimental device.Furthermore,two parallel displacement simulation experimental devices were used to optimize the displacement effects of particle size,injection concentration,injection volume,permeability gradient and injection timing.Finally,the concept of "liquid flow partial steering" is put forward.Based on the capillary bundle model,the quantitative calculation model of fluid flow flexible steering by surface deposition of nano-micron microspheres is established,and the evaluation method of the ability of nano-micron polymer microspheres to adjust flooding by surface deposition is established.The experimental results show that the polymer microspheres have obvious expansion multiple of particle size at reservoir temperature(60 ?).The cross-linking between the microspheres results in the increase of the viscosity of the microspheres.Under the experimental conditions,the oil recovery is the highest when the flow rate is 0.5mL/min for single pipe displacement.When the flow rate is 0.1 mL/min,the plugging efficiency is the highest.The optimum injection rate is 0.5mL/min in combination with the specific injection rate in the oilfield.The displacement effect of polymer microspheres with particle size of 100 nm is the best when two parallel tubes are connected.The optimum injection concentration was 2000 mg/L.The optimum injection rate was 0.3PV.The permeability gradient ranges from 2.24 to 5.32,and the polymer microspheres have a good effect on enhancing oil recovery.Permeability gradient less than 2.24 tends to homogeneous reservoir.The permeability is more than 32.50,and the low permeability model has no liquid.The optimum injection time is dynamic water content of 80%.The results of this study can be used for reference and reference in field application for the optimization of injection parameters of polymer microspheres for profile control and flooding.The research results of "partial flow steering" mechanism further enrich the mechanism of polymer microspheres regulating fluid flow steering.