Abstract

Stability of nature gas hydrates (NGH) is greatly impacted by temperature. Because intense heat is released from cement hydration during well cementing, limiting the temperature rise of cement is critical for safe cementing of NGH well. The total heat release by cement slurry has a strong correlation with the mechanical properties of cement slurry. Consequently, reducing the heat of hydration of cement means typically results in lower strength of the cement stone. Traditional evaluation methods do not fully consider the complex interaction between cement hydration reaction and heat transfer in the wellbore, therefore, it is difficult to determine whether the cement slurry formula selected is suitable for well cementing in nature gas hydrates. In this paper, a model to predict cement wellbore temperature was developed by incorporating the complicated interactions between temperature and cement hydration reaction. The model established the relationship between degree of cement hydration and wellbore temperature based on the cement hydration reaction kinetics. Coupled with differential method and numerical calculation, the influence of wellbore temperature on NGH was analyzed during the cementing process. The newly developed model was used to predict the field performance. Model predicted data and field data are within 10.0%. By accurately predicting the change of NGH with wellbore temperature during the cementing process, the model in this paper can not only effectively guide the research and development of low hydration heat cement slurry for NGH well but also find and avoid safety hazards in time during the design process of NGH cementing slurry.

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