Properties of oil well cement with high dosage of metakaolin

This research work was carried out to evaluate the properties of oil well cement with high dosage of metakaolin. The fresh pastes were made using an initial water/solid ratio of 0.5 by weight and then hydrated for periods up to 56 days. The mechanical performance was assessed from compressive strength. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were applied in order to study the hydration products and qualitative of microstructure. Feasibility as oil well cement of metakaolin replaced cement was assessed by thickening time, corrosive fluid exposure, density and rheology test. Test results confirmed that the early-term strength decreased with the increasing metakaolin content and the set cement with more metakaolin showed higher long-term strength at 75 °C. The cement pastes with 40-60%wt metakaolin presented good strength both in early-term and long-term curing at 150 °C and above. The metakaolin replaced cement pastes demonstrated low porosity and good strength due to stable hydration products and dense microstructure. Meanwhile, the filling effect of metakaolin partials reduced porosity and improved corrosion resistance of hardened pastes. The MK replaced cement pastes are applicative for the cementation of deep wells, acid rich wells and geothermal wells.