Laboratory Study on a New Low Heat Cement

Shallow hydrate zones are often encountered in offshore deep drilling. Conventional low temperature cement releases quite large amount of heat which, during well cementing, will negatively affect the quality of well cementing because the heat released causes the hydrate zones to destabilize. A special low heat aluminophosphate cement has been prepared in laboratory, and is compounded with high belite sulphoaluminate cement and slug cement to form a new low heat cement-the APE cement. A low heat cement slurry suitable for cementing deep water wells with shallow hydrate zones is prepared by mixing the APE cement and cement additives of independent intellectual property, such as low temperature filter loss reducer, early strength agent and dispersant. The heat of hydration of this cement slurry at density between 1.40 g/cm³ and 1.60 g/cm³ is less than 200 J/g. Set cement aged at 10℃ for 24 h has compressive strength of 3.5 MPa. Filtration control of the cement slurry is less than 50 mL, better than that of the conventional cement slurries. φ₃₀₀ reading of the cement slurry is less than 300. The new cement slurry has 3 d heat of hydration that is 58 J/g less than that of the conventional low heat cement slurries, and thickening time that is adjustable. Laboratory experiment shows that the new low heat cement slurry has, at low temperatures, low heat of hydration, high early strength, low filtration rate and good thickening property, and is able to satisfy the requirements for cementing deep water wells penetrating hydrate zones.