Abstract
To improve the resistance to CO2 corrosion of oil well cement, soap-free emulsion polymerization was used to prepare a soap-free latex (PSAC) with sodium styrene sulfonate (SSS) and nano-SiO2 (SSS/SiO2) as the ionic copolymer emulsifier. The effects of SSS/SiO2 on the performance, thermal stability, and latex particle morphology of the PSAC were investigated through zeta potential, TGA, and TEM measurements, respectively. The carbonation resistance properties of cement with PSAC were evaluated, and the anticorrosion mechanism of the PSAC cement was determined by SEM, EDS, XRD, and 29Si NMR analyses. The results showed that the PSAC particle size was uniform, the particles were monodispersed, and they had a typical core-shell structure and good heat resistance. The carbonation resistance test results showed that after 60 days of corrosion, the corrosion depth of the cement with 12.0% PSAC content was only 2.16 mm, the permeability was 0.0018 mD, and the decrease in the compressive strength was 6.65%. The porosity in the cement was reduced significantly, and the pore volume (>50 nm) of the cement was reduced by 0.24 times. The PSAC film formation decreased the contact between hydration products and CO2. In addition, the nano-SiO2 in the PSAC reacted with Ca(OH)2 to reduce the free Ca(OH)2 content in the cement and generate C-S-H gel with a low Ca/Si ratio and high polymerization, which did not react as readily with CO2.