Regulation of oil well cement paste properties by nanoclay: Rheology, suspension stability and hydration process

•The nanoclay strengthened the grid structure assembled by charged copolymer and nanoclay and cement colloidal particles.•The addition of nanoclay can significantly the suspension stability of cement paste under high temperature.•The nanoclay colloidal particle promoted cement hydration and improved mechanical properties of hardened cement stone.•The nanoclay colloidal particle can serve as the nucleation sites for generation of CSH.