Effect of plain and carboxylated styrene-butadiene rubber on the rheological behavior of silica fume-class G Portland cement slurries

The incorpation of a high pozzolan content in cement systems enables an enhanced thermal stability. In an even harsh condition, where imposed deformations occur in addition to high temperatures, it is desirable that cementitious systems present high ductility, which can be achieved for example by adding polymers. The aim of this paper, is to better understand the rheological behavior of ductile cement slurries, designed for oil wells subjected to cyclic steam stimulation. The studied cement formulations contain Silica Fume and two different copolymers (Styrene-Butadiene and its carboxylated version). The influence of each copolymer content on the rheological parameters was investigated. Isothermal calorimetry was used to measure the induction period to guarantee that rheological parameters were carried out in the same hydration period. As the rheometer test was carried out in a non-isothermal condition together with a vane applied shear rate, increased reaction rates are expected. However, it is plausible to assume that the pastes remained in the induction period otherwise they would be in the acceleratory period where pastes start to set. Attempts have been made to correlate properties found by rheometry in the mini-slump test. It was observed that the XSBR delays and decreases the ettringite formation in the first hours of cement hydration, leading to lower yield stress values and increased viscosity and thixotropy. Good correlations were established between parameters measured by rheometry and mini-slump tests, which show promising results for potential use in on-site yield stress and plastic viscosity tests in Oil Well applications.