Well cementing material

14) A method of producing a foamed cement slurry, wherein the following stages are carried out:

• mixing a powder with water comprising a hydrosoluble polymer thinning agent so as to obtain a cement slurry, the powder comprising a hydraulic binder, microparticles and mineral particles, the hydraulic binder being selected from the group consisting of class G Portland cements, class H Portland cements, aluminous cements whose alumina content is at least above 30% by mass, and sulfoaluminous cements, the microparticles being selected from the group consisting of microsilica particles and silico-aluminate particles, of grain size ranging between 0.1 and 30 μm, whose proportion ranges between 15% and 50% by mass in relation to the mass of hydraulic binder, the mineral particles having a grain size ranging between 1 and 500 μm, with a proportion ranging between 10% and 35% by mass in relation to the mass of hydraulic binder, the proportion of particles being lower than the proportion of microparticles, the hydrosoluble polymer thinning agent having a proportion ranging between 0.1% and 8% by mass in relation to the mass of hydraulic binder,
• introducing a foaming agent in the cement slurry, the proportion of foaming agent ranging between 0.1% and 10% by mass in relation to the mass of hydraulic binder,
• pumping the cement slurry comprising the foaming agent, and
• injecting a gas into the cement slurry comprising the foaming agent and stirring the mixture of slurry and of gas so as to foam the slurry and to obtain a foamed cement slurry.