Synthesis And Application Performance Evaluation Of Thermosensitive Polymer Microspheres

With the long-term water-flooding development of the reservoir,the formation heterogeneity continues to increase,and the reservoir environment continues to deteriorate.At present,it is difficult for the existing profile control agents to meet the on-site construction requirements in the face of the complex environment in the deep formation.Therefore,it is urgent to develop plugging control agents that match deep formation conditions such as high temperature and high salinity,so as to realize their deep plugging control in reservoir development operations.The polymer microsphere plugging control agent has been widely used in oilfield production due to its good performance in the early stage.However,with the deterioration of the formation environment in the later stage,the microspheres used for deep plugging control showed poor temperature resistance and poor salt resistance,and the expansion time too fast etc.Therefore,the purpose of this thesis is to develop a polymer microsphere that can withstand high temperature and high salt,and can achieve slow expansion and slow release deep migration.In this thesis,conventional polymer microspheres P（AA-AM）were prepared by inverse emulsion polymerization with acrylamide（AM）and acrylic acid（AA）copolymer as monomers.The polymer yield and particle size were optimized by adjusting the oil-water ratio,emulsifier ratio,stirring speed,temperature,and initiator dosage.Then KH-570 was used as modifier to modify Ti O₂ to improve the lipophilicity.On the basis of P（AA-AM）polymer microspheres,the inorganic/organic composite microspheres P（AA-AM）@Ti O₂ were prepared with modified Ti O₂ as inorganic material.Finally,P（AA-AM-SA）@Ti O₂ microspheres were prepared by using sodium alginate as temperature-sensing coating material and calcium chloride as ion gel reaction.The film-coated microspheres can migrate to the deep part when the temperature is low,and the film cracks when reaching the high temperature environment in the deep formation,and the inner microspheres rapidly absorb water and expand to achieve the purpose of slow expansion and slow release.The structures and morphologies of the three prepared microspheres were analyzed by SEM,EDS,FT-IR,and TGA.At the same time,three kinds of microspheres were tested for their temperature and salt resistance,viscoelasticity and other properties.Finally,the effect of three kinds of polymer microspheres on profile control and water shutoff was evaluated.The main research conclusions are as follows:（1）When the oil-water ratio is 8:5,the emulsifier ratio is 6:2,the monomer ratio is2.8:2.2,the initiator dosage is 0.6%,and the p H value is 7,the three kinds of microspheres are successfully synthesized.The size of the microspheres observed by SEM was 10～30μm.EDS and EDS-Mapping showed that the Ti element was successfully polymerized on the microspheres,and the observation of the P（AA-AM-SA）@Ti O₂ microspheres showed that the Ca element was evenly distributed on the microspheres,indicating that it not only had a coating effect,but also cross-linked with the microspheres themselves.The structures are connected to each other through physical cross-linking,entanglement,etc.FT-IR,TGA,etc.indicated that the microspheres were the target product,and the microspheres containing modified Ti O₂ had better thermal stability.（2）Compared with P（AA-AM）microspheres,the Ti O₂ reinforced polymer microspheres have better dispersion stability,temperature and salt resistance.The optimum conditions for use are at a salinity of 1.5×10⁴ mg/L above 90℃.At the same time,the pyrolysis temperature of the thermal material is 90℃under the simulated formation environment.（3）The microspheres have good injectability between the permeability of1.23～2.35μm²,and a good plugging effect near the permeability of 2.20μm².At high temperature and high salinity,P（AA-AM-SA）@Ti O₂ microspheres have a remarkable effect on profile control and water plugging,the plugging rate reaches 95.3%,and the oil recovery rate is increased by 12.89%compared with water flooding,achieving the effect of slow swelling and slow release.