Use of scleroglucan as an additive for high temperature cement slurries.

An oil well cementing process, gas well or geothermal well, wherein is injected under suitable conditions appropriate drilling fluid, and optionally a buffer fluid and finally a composition comprising water, a cement, at least one viscosity additive, optionally at least one retardant compound and optionally at least one silica characterized in that said additive is a scleroglucan solution. It applies especially to cementing wells at high temperature.