Research of Influences on Second Interface Cementation Performance in Well Cementation of Adding Metakaolin into Drilling Fluid

It is difficult for conventional drilling fluid filter cake to form integration cementation with cement sheath, which causing weak cementation of the second interface. Therefore the following researches on improving the second interface cementation strength were carried out based on alkali activation mechanism of metakaolin. Cementation strength between metakaolin drilling fluid filter cake and cement sheath has been observed; the mechanism has been analyzed through SEM, XRD and FT-IR; engineering application performance of metakaolin drilling fluid has been studied; and circulation time of the technology has been researched. The results of the experiments showed that: 1) adding metakaolin into drilling fluid was helpful to improve the second interface cementing performance; 2) calcium hydroxide produced by cement hydration inspired metakaolin to generate C-S-H gel and realized overall cementation of filter cake and cement sheath; 3) through select particle size of metakaolin matched with other solids in drilling fluid, drilling fluid performance index could meet requirements of engineering application; 4) and for best results, the circulation time of metakaolin drilling fluid should be more than 40 minutes. The results prove that metakaolin drilling fluid can improve the second interface cementation performance, showing feasibility on flied using and practical values on improving wellbore integrity.