Compensated-contraction binders for offshore well cementation - contg Portland cement, gypsum and aluminous cement

摘要

Compensated-contraction binder compsns. for use in offshore drilling operations (esp. for cementing oil wells) contain (a) 94-98 wt% of a mixt. of 88-92% Portland cement (particle size 2600-3100, pref. 2700-2900 cm2/g) and 8-12% gypsum, with an SO3 content of 4.5-5.5%; (b) 0.5-1.5 wt% of aluminous cement with a particle size of 3400-4000 (pref. 3600-3900) cm2/g; and opt. (c) 2-4 wt% of overbaked gypsum in an amt. sufficient to adjust the total SO3 content to 5.5-6.5%. The compsns. have good pumpability, expand very slowly (e.g. reaching expansion values of =2000 mu/m in 28 days or more), and have good resistance to cracking.