API well cement is becoming difficult to obtain in many parts of the world. In newer operating areas, API monogram well cements have never been available, while in others, plants previously producing API well cements are choosing to drop such production. This lack of quality API well cement is forcing operators to consider using Non-API (ASTM) cements in applications beyond their previously recommended limits. While the use of ASTM cements in certain applications such as shallow/cool casings is not new, the migration of use into areas approaching what many consider to be HTHP applications is.

Because they are not just "re-named API well cements", using ASTM cements in more rigorous applications presents new challenges. These include best slurry density, viscosity/gellation issues, thermal stability, corrosion resistance, and reproducibility of data, to mention a few. Moving beyond historical comfort areas of operators requires a new mind-set be established to successfully apply non-API cements in more challenging environments. Operators and service companies must ask difficult questions such as why use slurry densities in the 1.8 to 1.98 sg, if not required for well control? What strengths are really needed to provide isolation and casing support? Can ASTM cements perform adequately at elevated temperatures? Answering these questions, and changing old paradigms on the way cements are designed is the aim of this paper.

The authors provide information on optimum densities for ASTM cements replacing API Class "H/G", and "C" cements. They also introduce new materials allowing for mixability, performance and safe use of ASTM cements at temperatures > 149°C. This information includes thermal-stability, strength development, mechanical properties, and gas control data.

Test data will be shown to support conclusions and help change paradigms on designing with ASTM cements for use in more widespread high-temperature applications.

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