Cement sheath is a critical piece when constructing a well for long-term competence. The ability of the cement to block annular fluid flow has both economical and environmental implications. Examples of uncontrolled movement of formation fluids through a leaking cement sheath include unwanted water migrating to the perforations, hydrocarbons escaping to a lower-pressure reservoir, and hydrocarbon-based fluids flowing to environmentally sensitive water zones or to the surface.

Throughout the years, several advances in cement technology have been introduced to help ensure zonal isolation is maintained throughout the operational life of the well. Such advances include the design of cement with mechanical modifiers tailored for a specific well type and anticipated loads on the cement. Today, a new cement system is being introduced. This system aims to help assure zonal isolation, even if the cement is loaded beyond its capacity resulting in cracks, micro-annuli, or pathways for wellbore fluids to migrate. The new system works on the premise that the migrating fluids react with the damaged cement system resulting in the cement automatically sealing the cracks to help prevent further fluid migration.

The purpose of this paper is to illustrate simple evaluation techniques that allow for quantification of auto-sealing cements in a simulated static or dynamic-downhole environment. Experimental apparatus used consist of a standard annular ring mold used for expansion/shrinkage measurements as well as a cement fluid-loss test apparatus with a specialized insert designed for continuous flow past the cement test specimen. The capability of the cement system to react to the flowing fluid and ultimately reduce the flow is monitored. Results of various cement systems reacting with fluids under a range of simulated downhole conditions are presented.

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