Polinaftaleno Sulfonato de Sódio e Policarboxilato: um estudo comparativo entre suas propriedades dispersantes em pastas de cimento para poços de petróleo

Abstract

Flowability is considered one of the main properties of fresh cement pastes and is essential for achieving the appropriate rheological parameters for a primary cementing operation of a well. Dispersants are a class of essential slurry additives as they prevent flocculation of cement particles and reduce the slurry viscosity, significantly improving its flowability and pumpability. Pastes containing two types of dispersants, Sodium Polyphthalene Sulphonate and Polycarboxylate, were prepared at different concentrations in order to investigate the differences between their dispersion mechanisms and to compare the rheological parameters obtained by each one. The tests were all performed according to API 10B standard on a Chandler 3500 rotary viscometer simulating a well with a depth of approximately 500 m (T = 87 ºF). The results showed that the polycarboxylate promoted a greater reduction of plastic viscosity, yield limit and final and initial gels than the polyphthalene, due to its additional mechanism of dispersion by steric repulsion between its long polymeric side chains.