Cement Slurry Design to Prevent Destabilization of Hydrates in Deepwater Environment

Abstract

Abstract Hydrates present challenges to drilling, cementing, and producing in deepwater environments. If the hydrates are destabilized during well operations, gas or solids could rise to the surface and create problems. Therefore, there is a compelling need to prevent destabilization of hydrates from drilling to producing operations in the life of the well. The volume of cement slurry in the surface casing is great because of the large annulus, and this slurry volume results in a great amount of heat generated during slurry hydration. Further, during production hydrocarbons could increase the temperature of the surrounding formation. These factors could destabilize the hydrates. Cement slurries are designed to lower the heat of hydration while meeting or exceeding the other properties needed for successful deepwater cementing. Heat of hydration is reduced by a factor of more than two when compared to the conventional cement slurry design. The improved cement slurry designs lower considerably the thermal conductivity of the set cement sheath. Laboratory tests designed to measure and optimize the heat of hydration are discussed and field implementation of these slurries and results are presented. Results presented in this paper should help the industry construct and produce wells without destabilizing the hydrates, thus promoting well safety and economics.