Oilfield-cement compositions capable of self-healing cracks/fractures in set cement without depending on contact with a fluid, such as water or oil, have been developed. Traditionally, such compositions include additives that are capable of swelling when exposed to fluids like water or oil, for example. Presumably, if the cement develops cracks/fractures or flow channels caused by shrinkage or debonding and allows fluid flow, the swelling additive exposed to such fluids will swell, thereby healing the flow path. The current technology employs additives that swell either in water or oil, but not both. Such additives do not swell when exposed to gas, irrespective of whether the gas is carbon dioxide or a hydrocarbon. Dependence on additives to swell and block flow channels after contact with a specific type of fluid hinders the self-healing effectiveness of the cement composition. As a result, designing cement compositions for field applications requires prior knowledge of the type of fluids that the cement may come into contact with, not only through the productive lifetime, but also after abandonment of the well. Alternately, multiple additives that will swell and seal in both water and oil might need to be included in the initial cement design. Even in the latter case, the compositions still cannot offer protection against gas flow. A new class of elastomeric additives that do not depend on the nature of fluid to seal cracks is presented in this paper. Performance of these additives in a variety of self-healing tests based on flow studies through cracked cement cores will be presented. In addition, the importance of specific structural features of the additives that render them suitable for inclusion in self-healing cement compositions will be discussed.
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