Effect of nanosilica on the mechanical properties of oil well cement at low temperature

Abstract

Low temperatures affect the development of cement slurry strength in cementing operations, thereby increasing the risks of shallow water/gas channelling and operation costs. Accelerators such as calcium chloride are often used to rapidly improve the mechanical properties of cement. However, accelerators often have negative effects, including decreased cement stone volume, increased permeability and decreased protection against sulfate corrosion. The effects of nanosilica (NS) on the properties of cement slurries were studied at low temperatures. It was found that the early strength of cement slurries was significantly enhanced with the addition of NS. Furthermore, sedimentary stability and the ability to control fluid loss were improved at low temperatures. Mechanistic analysis showed that the early strength improvement was primarily due to the pozzolanic effect of the NS and the bridging and pull-out effects of the AFt (Al2O3-Fe2O3-tri) phase. The use of NS as an accelerator for low-temperature cementing may have broad applications.