Cement Systems require conformance of specific parameters for the longevity of the system placed as a sheath. Challenges of the system design are exacerbated considering the environment for placement of the sheath. HPHT cement systems require special design attention, and the authors propose to share one such case history in designing of the HPHT system for Eastern India Offshore.

HPHT cement systems require not only modified testing procedures, but products also. HPHT cement system products are required to withstand BHST temperatures for the life of the well without considerably altering the slurry system properties. Modified test procedures and products requirements for slurry system bring additional logistical challenges like preparation and availability of right cement blend for testing and preparing the slurry system for the application.

Considering the temperature gradient of 2.23°F/100ft, bottom hole static temperature (BHST) for the 7" liner job was 467°F. The mud weight for the section was planned between 14-16 ppg (1.67 to 1.9 sg). Computed BHCT alone was considered inadequate and determination of the hot spot in the wellbore was required. Computerized simulator was used for the purpose. Results show that the hot spot temperature predicted by the simulator was higher than the computed BHCT and the depth of the hot spot was shallower than TVD as normally anticipated. The simulator runs are recommended for determination of hot spot for HPHT testing of cement systems in particular. The simulator considers effects of various fluids pumped and their contact times along with the heat capacities during the application.

Product choice for preparation of the Cement systems used earlier for the high temperatures encountered in Western India offshore were reviewed and preliminary testing was carried out on the basis of the prognosed temperature. However predictions from the temperature simulator yielded higher temperatures for the East coast well. This required a different product set for the cement system design.

The authors feel that the review of this case history and the design challenges at this technology meet shall potentially benefit the design engineers in understanding and enhancing their knowledge about design practices for HPHT cement systems.

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