Preparation And Properties Of Silica-Reinforced Polymer Microsphere For In-Depth Profile Control

With the rapid development of the world economy,the demand for petroleum resources is increasing.However,the deepening of oilfield development aggravates the heterogeneity of the reservoirs,and the water logging and breakthrough are serious,leading to an inefficient circulation of injection water.As a result,the remaining oil is generally distributed,and the water cut of reservoirs is increasing,which greatly affects the further development of oilfields.In-depth profile control technology is an effective solution to this problem.And due to the excellent formation compatibility and elastic deformation ability,the polymer microsphere plugging agents can realize in-depth profile control,increasing well production.Nevertheless,as the reservoir environment becomes more and more harsh,they gradually reveal poor temperature and salt resistance,and are prone to shear breaking and show low plugging strength.Therefore,a class of excellent composite microspheres for the profile control and water shutoff operations in complex formations were synthetized by in-situ polymerization in the dissertation.Firstly,the nano-silica was modified by polymerizable hydrophobic modification with the silane coupling agent 3-(methacryloyloxy)propyltrimethoxysilane as modifier.Infrared spectroscopy,micromorphology and sedimentation experiment indicated that the reactive groups were successfully grafted onto the surface of Si O₂,providing the basis for subsequent composite reaction.Secondly,the silica-reinforced polymer microspheres PNSCMs were synthesized by in-situ polymerization of acrylamide,acrylic acid comonomers and nano-Si O₂through inreverse suspension polymerization method.The process parameters were optimized by the yield of microspheres.Infrared spectroscopy,micromorphology and elemental analysis indicated the successful synthesis of microspheres.On this basis,the effects of Si O₂ loading and modification degree on the physicochemical properties of microspheres were studied,and the corresponding influence mechanism was proposed.Finally,the plugging and migration capacity and the profile control and oil displacement effect of PNSCMs were calculated by the formation compatibility experiment,the macroscopic migration experiment and the single-and double-tube oil displacement experiment.The results show that the initial particle size of PNSCMs is about 10-25?m and the sphericity is high.By adjusting the Si O₂ loading and modification degree,the swelling property of PNSCMs can be well regulated,weakening the environmental sensitivity.The thermal stability,shear resistance performance and viscoelasticity are also enhanced.Moreover,the dispersion stability and the synergistic effect between PNSCMs and partially hydrolyzed polyspermidine(HPAM)have also improved.There are three migration modes of PNSCMs in the formation pore:blocking,deformation passing mode and directly passing mode.PNSCMs have good migration ability and can form a dynamic plugging process of“plugging,migrating,re-plugging,and re-migrating”.Due to the good viscoelasticity and strength,PNSCMs can migrate into the deep part of the reservoirs under the displacement pressure and achieve effective plugging in high-permeability channels.So that,the subsequent injection water will be diverted into the low-permeability channels and the low-permeability layers which are not affected by water flooding,so as to improve crude oil recovery.This research aims to provide the theoretical guidance and technical support for the development of organic/inorganic composite plugging agents.