Effet des conditions environnementales sur les propriétés mécaniques d'un ciment de puits géothermique

In a geothermal well, a cement sheath is placed between the casing and geological formation for support and sealing purpose. Environmental factors such as temperature, pressure and the presence of NaCl in the fluids in Dogger aquifer can potentially affect the hydration of cement. A maturation cell is developed at IFSTTAR to study the effects of environmental conditions on the properties of the hardened cement paste. Ultrasonic wave velocity measurements and Young modulus tests are performed on specimens prepared in the cell under various pressure/temperature conditions, with or without NaCl in the surrounding fluid. The results show a significant reduction in the mechanical properties of the hardened cement paste with increasing hydration temperature between 20°C and 90°C. An increase in the pressure to 20 MPa and the presence of NaCl at 20°C show no significant influence on the mechanical properties.