Type DB expandant for oilwell cement

A new expansive agent, Expandant DB, is developed for use in oilwell cementing to prevent gas-channelling and poor bond quality. The expansion and performance properties of an oilwell cement slurry system with 0 - 8% DB added are determined and investigated in the course of setting at different conditions. It is shown that introducing 3 - 8% DB leads to expansion of the slurry system from fresh to hardened stages, significantly improves its compression and bonding strength under restrain conditions, and exerrts no negative effect on its performance properties. DB is well compatible with common cement additives. The expanding cement can be used in wells of temperature at least.up to 80°C. The expansive mechanisms involved are acceleration of developing plastic strength and creation of crystal growth pressure by the reaction products of DB with cement hydrates and mixing water.