Abstract: Methods and compositions for treating a formation, proximate a wellbore, prior to primary cementing, by reacting an activating agent and a silicate to provide a barrier between the wellbore and the formation to reduce the contamination of cement by ingress of formation fluids or leakage of cement from the wellbore during cement transitional phases. The activating agent may be provided while the wellbore is being drilled or may be provided subsequent to drilling or may be at least partially naturally occurring in the formation prior to drilling. The silicate may be provided during or subsequent to drilling.