Drilling through low pressure formations, either offshore or through depleted formations, requires the use of low density fluids to prevent lost circulation and as well as to properly place cement during cementing applications. Achieving these densities in cements can be done through foaming the cement, increasing water content, or through the addition of silica based microspheres. Each of these methods have individual limitations, and in the case of silica based microspheres, their specific fallback is a chemical instability with the microsphere itself reacting with the cement pore fluid. This chemical instability creates a hydrophilic gel that is expansive and creates fractures in the cement as it expands, which is more formally referred to as alkali-silica reactivity (ASR). Prevention of ASR involves the application of additives to the cement that acts as a sink for the alkalinity in which prevents the expansion of ASR. A specific application that this paper investigates for this prevention is the use of Lithium nitrate. This study looks at the effects of a high alkalinity environment onto the microspheres by visualizing the reactions that are occurring using Scanning Electron Microscopy (SEM), and confirming the presence of ASR when silica based microspheres encounter a high pH environment. Then cement samples were created to compare the effects lithium nitrate has on cements created with silica based microspheres. SEM and micro indentation was conducted on these samples, which showed that lithium nitrate prevents reactions, but after 28-day hydration a loss of mechanical properties is present.
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