Abstract

The two principal functions of oilwell cementing are to restrict fluid movement between zones within the formation and to bond and support the casing. Apart from these, the cement sheath also protects casing from corroding, protects the casing from shock loads when drilling deeper, and plugs lost circulation or thief zones. Once cement is placed in the wellbore, initial setting occurs wherein development of compressive strength becomes more important for further drilling operations. Early strength development is important to help ensure structural support to the casing and hydraulic and mechanical isolation of downhole intervals. Delays in strength development cause significant amounts of lost time because of the need to wait on cement (WOC). Typically, an accelerator is often used to enable early strength development in cement. It is desired that an accelerator should improve overall compressive strength without causing excessive gelation.

Nanomaterials (being smaller in size and higher in surface area) are used in several fields, including catalysis, polymers, electronics, and biomedicals. Because of a higher surface area, these materials can also be used in oilwell cementing to accelerate the cement hydration process. Moreover, they are often required in small quantities. This paper documents a case in which nanosilica was used in cement formulations to develop high early strength. Nanosilica also helps enhance final compressive strength and helps control fluid loss. Using the correct quantity of nanosilica, it is possible to design cement slurry with low rheology and good mechanical properties while controlling fluid loss.

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