Process for preparing an oil-well cement slurry

A process for preparing an oil-well cement slurry, the process comprising:

• (a) hydrolysing a precursor and an accelerator in a medium to obtain a colloidal suspension of silica nanofluid comprising size-controlled silica nanoparticles, wherein the hydrolysis comprises the steps of:
• adding a predetermined volume of the precursor to the medium at a predetermined flow rate and at a predetermined interval for every 25% incremental addition of the predetermined volume of the precursor;
• adding a solvent dropwise after every 25% incremental addition of the predetermined volume of precursor to the medium to obtain a mixture;
• heating the mixture at a predetermined temperature for a predetermined duration;
• adding a predetermined volume of the accelerator dropwise for a predetermined duration to the mixture to obtain a colloidal suspension of silica nanofluid comprising size-controlled silica nanoparticles having a particle size in a range from 5-300 nm;
• (b) adding a predetermined amount of water to silica nanofluid to obtain a base fluid;
• and
• (c) adding cement to the base fluid at a cement to base fluid ratio of 100:45 to obtain an oil-well cement slurry comprising size-controlled silica nanoparticles.