The Influence of In Situ Polymerized Epoxidized A/F Bisphenol-Chitosan on Features of Oilwell Cement Slurry—Molecular-Level Analysis and Long-Term Interaction of API Fracturing Fluid

摘要

A novel oilwell cement slurry was prepared with in situ polymerized epoxidized A/F bisphenol–chitosan and characterized by ~(29)Si NMR and EPR spectroscopy. The hydrated and cured cement slurry evidenced the presence of unreacted clinker phases identified by the presence of orthosilicate groups along with the presence of hydration products identified by short linear polymeric silicate units typical of calcium silicate hydrate (C-S-H). Two main Fe~(3+) domains and Mn~(2+)-related hyperfine sextets were detected by EPR spectroscopy. After long-term contact with an API acidizing fluid, the features of the ~(29)Si NMR and EPR spectra did not change appreciably. The kinetics of overall solids dissolution upon contact with the hot acidizing fluid was modeled with the Avrami-Erofe’ev equation. The kinetic parameters are not very sensitive to changes of temperature. The values of the Avrami exponent suggest that diffusion-controlled processes without chemical reactions govern the overall rate of interaction processes or are partially involved in it. The results indicate that the A/F bisphenol–chitosan polymeric network can improve significantly the chemical stability of cement slurries in the presence of acidizing fluids and may be a good option for oil and gas industry.