The impact of powerful retarding additive synergies on the kinetic profile of cementitious mineralogical transformations
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The impact of powerful retarding additive synergies on the kinetic profile of cementitious mineralogical transformations at high temperature Peter J. Boul, Diana K. Rasner, Kenneth D. Johnson, and Carl J. Thaemlitz, Aramco Services Company, Aramco Research Center – Houston, 16300 Park Row Blvd. Houston, TX 77084, USA Address all correspondence to Peter J. Boul at [email protected] (Received 19 March 2019; accepted 21 May 2019)
Abstract Powerful synergies between phosphonate, zinc oxide, and acrylamido-tert-butyl-sulfonate (ATBS) copolymer chemical additives render superior performance in a high-temperature retarder system for oil well grade Portland cement. The phosphonate retarder and ATBS-based retarders establish a two-tiered strength development where amorphous C-S-H converts to crystalline dicalcium silicate hydrate (C2SH) in the first (low compressive strength) tier prior to the reaction of Portlandite with quartz. The three additive retarder system can be tuned with nanosilica to eliminate the two-tiered strength development effect leading to a smooth transition from the cement in the slurry form directly to its highest compressive strength.
Introduction Portland cement additive chemistry is fundamentally important to oil and gas well construction and to ensure zonal isolation throughout the life of an oil well. When sealing the casing to the wellbore formation with cement, oil well cement additives regulate many important slurry properties including rheology, suspension stability, cement slurry fluid loss control, set time, and mechanical properties of set cement.[1] Poor engineering of oil well cement slurries can result in the loss of zonal isolation in a well potentially leading to the loss of a well and considerable hazard to field personnel.[2] The appropriate selection of the additives in cement slurries depends on the temperature and pressure profiles down the length of the well, the depth of the well, the geologic formations that the slurry contacts, as well as the presence of gas, water, and oil in the different zones of the well.[3–5] The understanding of cement chemistry and cement additive chemistry is critically important for the appropriate design of oil well cements used in wells with these well-specific parameters.[6] There are many kinds of cement additives used in well cementing. The additives can be classified by the function that they impart into the cement for oil and gas well cementing operations. For example, fluid loss control additives are typically polymeric species that prevent the loss of water from the cement slurry into the rock formations surrounding the cement where it is placed. Some of the additives which are among the most used in well cementing are accelerators, fluid loss control additives, suspension aid additives, and retarders.[7] Retarding additives are added to cement slurries to delay the setting (hydration) time of the cement.[8] This is very important in well cements
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where the different thermal conditions in the well can give correspon
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