| With the decreasing of oil reserves,how to enhance oil recovery is becoming more important.The surfactant is widely used in enhanced oil recovery(EOR),which reduces the oil-water interface tension significantly,and changes the wettability of rock surface.However,during the process of formation migration,the surfactant will be adsorbed with the formation of rock and soil,which results in the decrease of concentration.Strong adsorption retention problems lead to a large amount of surfactant loss,which reduce the flooding efficiency and bring a higher cost.To avoid the loss of surfactant adsorption has became an important problem in EOR.Because of the special cavity structure,intelligent microcapsules are widely used in medicine,food,cosmetics and other fields,which have many advantages,such as good embedding,the larger specific surface area and so on.However,it has not been reported in the literature that surfactant was embedded in the intelligent microcapsules to avoid the loss of adsorption.In this paper,combined with microfluid technology,two kinds of microcapsules of penetrability and temperature response were prepared,which used the environmentally friendly monomer N-methylol acrylamide as substrate,and used the O/W/O emulsions as template.The preparation methods of two kinds of microcapsules and the influence of various factors on the pattern and performance were systematically studied.First of all,two levels of microfluidic device w set which was used to prepare O/W/O double emulsions,and the influence of emulsion formation on the different flow conditions and water phase viscosity were respectively investigated.Results show that,the stability of the prepared emulsion was better when the amount of PGPR was 3%,the amount of F-127 was 1%and the amount of PGPR was 8%.The double emulsions prepared under different flow rate and viscosity conditions had good monodispersity and narrow size distribution,and the particle size deviation coefficient(CV)were below 5%under different preparation conditions.By adjusting the relative velocity of various phase,which could precisely control the complex latex package number of droplets and droplet size.Under the condition of the stationary phase and the middle phase velocity,increasing gradually external phase fluid velocity,it could successively prepare double emulsions of one contain more,one contain two coexistence with one contain one,one contain one,one contain one coexistence with one contain zero.Under the precondition of generating stable O/W/O emulsions,the inner diameter of double emulsions was proportional to the Q1/Q2,and the external diameter of double emulsions was proportional to the(Q1+Q2/Q3).Under the conditions of same intermediate phase and the middle phase velocity,with the increasing intermediate water phase viscosity,inner diameter of emulsion preparation would gradually become smaller.This was due to the increasing cohesive stress of the internal phase and middle phase,and the"pull" effect was more intense,which resulted in the droplet formation time shorten,formation emulsion frequency increases,and the droplet size lessen.Accordingly,to form stable O/W/O emulsion,that need increase external phase's flow rate,and provided greater shearing action to middle phase.Secondly,based on microfluidic technology,we used the monodisperse O/W/O preparation emulsion as the template to prepare microcapsules which used N-methylol acrylamide as wall material.The influence of various factors on the microcapsule was studied.When the reaction time was less than 18 min,the monomer of emulsion didn't form microcapsule.This was due to photoinitiator in the induction period,which didn't trigger monomer polymerization.When the internal water phase and the middle oil phase density difference were not regulated,the prepared microcapsule existed serious eccentric,even rupture phenomenon.This was due to the oil phase density is less than water,and the emulsion is unstable in the process of reaction,oil core rises gradually,especially the heat intensify the thermal motion generated by the uv irradiation,which resulted in the eccentricity microcapsules.By adding the benzyl benzoate in the oil phase to adjust density,neutral good microcapsules were prepared.According to the Fick's first law,we established surfactants diffusion model and measured the coefficient of permeability of different wall thickness and crosslinking degree of the microcapsules.The results showed that with the decrease of thickness of capsule wall or the decrease of the crosslinking degree cystic wall,the coefficient of permeability increased correspondingly.At last,based on microfluidic technology,we designed and prepared a temperature response type intelligent microcapsules.First of all,we prepared the thermosensitivity microspheres using precipitation polymerization.Then we added the microspheres to N-methylol acrylamide solution as intermediate water phase to prepare the O/W/O double emulsions,and successfully prepared thermosensitivity microsphere which had the thermosensitivity microspheres "switch" in capsule wall through uv irradiation polymerization.The results showed that different VPTT thermosensitivity microspheres by controlling the type and amount of hydrophilic monomer which formed copolymer with N-isopropyl acrylamide were successly prepared.Taking thermosensitivity microspheres which prepared by pure N-isopropyl acrylamide auto-polymerization as an example,the microcapsules had good temperature responsiveness,and could change the permeability coefficient by changing environment temperature.The anionic surfactant sodium dodecyl benzene sulfonate(SDBS)package carier release experimental results show that because of the temperature response of thermosensitivity microspheres,the microcapsule which put up a faster release rate of surfactant under the conditions of the environmental temperature was higher than thermosensitivity microspheres VPTT.And with the increase of amount microspheres,the permeability coefficient of microcapsules also gradually increased. |
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