Preparation And Properties Of Polyacrylamide Microspheres Profile Control Agent

In present, the major oil fields in our country face challenges of high and stable yield due to the long-term use of water injection flooding technology, the well water rate gradually increase, which also induce to a serious impact on the follow-up work. The polymers microspheres of nanometer and micron grade expanded in water to form elastic microspheres after injected into the stratum. When these microspheres transferred to the matching throat,they can be attached to the holes, improving the heterogeneity of the stratum. And the oil recovery can be greatly improved.According to the demand of water shutoff profile control for polymer property, designing for the molecule structure, and selecting proper monomer and initiator system. Anionic polyacrylamide was prepared by inverse emulsion copolymerization of acrylamide(AM) and2-acrylamide-2-methyl propane sulfonic acid(AMPS). During reaction,(NH4)S2O8 and NaHSO3 were used as initiator, Span80 and Tweeen80 as emulsifier. Effects of many factors were discussed such as reaction temperature, amounts of initiators and HLB. The results indicated that the optimum conditions was: the reaction temperature was 25℃,the initiator content was 0.3wt%, HLB was 6, the monomer concent was 25wt%, the surfactant content was 6wt%, the ratio of oil-phase to aqueous-phase was 1. And the effects of emulsifier dosage and oil/water on inverse emulsion polymerization also be investigated.Scanning electron microscopy(SEM) and microscope were adopted for investigating the morphology of cross-linked polymer microspheres. The structure and size distribution were characterized by fourier transform infrared spectroscopy(FTIR) and dynamic light scattering(DLS) separately. And nuclear-pore films was adopted to investigate the matching relationship between pore size and diameter, the results indicated that the great plugging effect could be got only when the diameter of polymer microspheres had the good matching relationship withpore size. Moreover, the temperature resistance was investigated by thermogravimetry analysis(TGA). The results of TGA showed that compared to the homopolymers of acrylamide and the copolymer of acrylamide, the decomposition temperature of the cross-linked polymer was increased 60 and 20 degrees respectively and the temperature resistance was improved. Sand packed tube displacement was also used to test core plugging effect of cross-linked polymer microspheres with different concentration under different salinities, permeability and temperature of core. It was observed that the polymer microspheres had outstanding plugging effect on the stratum with different permeability.When the permeability was less than 1000 m D, the plugging efficiency was more than 90%.Although the polymer was sensitive to the temperature, it also had a relative great plugging effect when the environmental temperature reached 85℃. But the polymer had bad salt resistance when the salinity was only 6000mg·L-1.