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Solution for a Long-Standing Cementing Challenge—Intelligent Cement Set Control Additive
Industry has always found it challenging to cement long zones with a single slurry system. A huge temperature differential exists between the bottom and the top of a long cement column. Cement slurry designed for the circulating temperature at the bottom of the long column will sometimes fail to set at the low temperatures at the top of the cement column. These results in rig nonproductive time and in certain cases can lead to well integrity problems.
While setting unplanned kickoff plugs or plugging and abandoning wells, the bottom hole temperature may not be very well known. The slurry setting is sensitive to temperature, and the setting time can change substantially if the actual bottom hole temperature is different from that used for design. This leads to failure of the cement plugs. This issue is more pronounced around 200°F.
A new generation of engineered cement set control (ECSC) additive has been developed to successfully cement wells in the scenarios mentioned above. The additive works intelligently and not only provides sufficient placement time for bottom of long cement columns where temperature is higher, but at the same time allows for fast compressive strength development even at the top, where temperatures are lower.
A single slurry design incorporating the additive has been used successfully in setting multiple plugs at different depths, with varying bottom hole circulating temperatures, demonstrating the relative insensitivity of the retarder to temperature variation.
This paper discusses successful use of the additive in the field for setting multiple plugs at varying depths and temperatures using the same slurry design. Field cases with results related to the various applications will be provided.