The Effect of Neat Magnesium Oxide (MgO) as Expanding Additive on Cement Shear Bond Strength at High Temperature Up to 250oC

Abstract

Good bonding between cement and casing and between cement and formation is essential for effective zone isolation. Poor bonding will create problems in production operations both for oil wells and geothermal wells. Expanding additives, such as magnesium oxide (MgO) are used for improving primary cementing.

Based on the results of previous research, there is a dangerous temperature transition at 1500C, because the lowest compressive strength as well as shear bond strength of cement will be attained after 24 hours curing time. The presence of mud film on casing wall and mud cake on formation will decrease shear bond strength, and, for the composition without expanding additive, it may reach zero. However, by adding expanding additives, shear bond strength of cement will increase, because the improved bonding is the result of mechanical resistance or tightening of the cement against the casing and formation. There is no chemical bonding.