| In order to improve the mobility control ability of polymer solution in deep reservoir,scholars in domestic and abroad have developed a series of polymer for oil displacement,aiming at improving the effective viscosity of polymer solution in reservoir,so as to enhance oil recovery.For the purpose of improving the viscosity of polymer solution,the method of increasing the concentration of solution is generally adopted.However,due to the shear action at immediate vicinity of wellbore,the viscosity loss of polymer solution is large and the mobility control ability is weakened.In order to solve this problem,a polymer with host-guest structure was designed and synthesized by combining the structural advantages of dendrimer and host-guest interaction,and the synthesis conditions were optimized.The test results of polymer solution properties showed that the synthesized polymer had similar viscosity to HPAM in brine,but good temperature resistance,salt resistance and shear resistance,and good mobility control ability under the premise of low viscosity.In this paper,the third-generation dendrimer polyamide-amine(PAMAM)was modified for skeleton monomer,and mono-6-acrylamide-?-cyclodextrin(ACD)was prepared based on P-cyclodextrin as host monomer,while 6-acrylamide-hexanamide-adamantane(AHA)was prepared based on 1-adamantanamine as guest monomer.Copolymer PAMAM/AM/ACD/AHA was synthesized by free radical polymerization with skeleton monomer,acrylamide,host monomer and guest monomer in aqueous solution.The structure of each monomer and copolymer were characterized by infrared spectrum.The optimum conditions for the synthesis of copolymers were determined as follows:the total concentration of monomers was 20%,the concentration of skeleton monomer was 0.03%,the total concentration of host-guest monomers was 0.5%,the molar ratio of host-guest monomers was 1:1,the initiator dosage was 0.3%,and the reaction temperature was 20?.The solubility,thickening property,temperature resistance,salt resistance,shearing resistance,rheological property and microstructure of the copolymer PAMAM/AM/ACD/AHA were further studied.The results indicated that the basic dissolution time of partially hydrolyzed polyacrylamide(HPAM)and copolymer was 1.7h and 7.8h respectively,under the salinity of 9374.12mg/L.The solubility of the copolymer was poor and the solution viscosity was low.The solution viscosity of the copolymer with a concentration of 1750mg/L was 13.3mPa s,and the copolymer had good shear resistance.The copolymer had good temperature and salt resistance under the conditions of high temperature and salinity.The rheological results showed that the copolymer exhibited shear thinning behavior and behaved as viscoelastic fluid.The effects of solution concentration,permeability of porous media and injection rate on the mobility control ability of copolymer PAMAM/AM/ACD/AHA in one-dimensional sand packed model were studied by core flooding experiments.The results showed that the copolymer solution with a concentration of 1750mg/L is poorly injected into the sand packed model with a permeability of 500mD under the conditions of 65? and brine,while the resistance factor was 44.34,the residual resistance factor was 16.31 and the RRF of HPAM was 2.79 in the sand packed model with a permeability of 2000mD.When the permeability contrast was 5:1,the copolymer solution could establish flow resistance in the high permeability medium and increase the intake rate in the low permeability medium.With the increase of injection rate,the RF established by copolymer solution increased while the RRF decreased.Overall,the copolymer solution had good mobility control ability under the premise of low viscosity. |
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