High Temperature Corrosion Resistant Cement Slurry Used in Fire Soaked Well Cementing

Fire soaking production is an advantageous thermal production technology fast developed in recent years. This technology requires cement slurry to have the thermal stability above 550℃ and resistance to CO₂ corrosion, such as GWC-500S, a phosphoaluminate cement which was developed by adding phosphate, alumina powder, corrosion resistant agent and activator into an aluminate cement. A liquid filter loss reducer GWF-500L and an inorganic acid retarder GWR-500S have also been developed for use in the cement. A cement slurry was developed with these materials and the set cement was tested using XRD at 50℃, 300℃ and 600℃. Hydrates of the cement and their changes with temperature were analyzed. Set cement calcinated at 600℃ was analyzed using SEM for its profile. Changes in the strength of the phospho-aluminate cement after calcination at 550℃ for 7 d were evaluated. Resistance to CO₂ corrosion of set cement at 120℃ and a CO₂ partial pressure of 6.9 MPa was evaluated. It is understood through these studies and evaluations that the phospho-aluminate cement slurry has thickening time adjustable between 40℃ and 100℃, API filter loss of less than 50 mL, and good rheology. The set cement has the advantages such as:resistance to high temperature to 550℃, resistance to CO₂ corrosion, adjustable density, moderate thickness, good stability, and good compatibility with drilling fluids and spacers. The cement slurry has been successfully tried on well Yingshi X in a fire soak test block in XX oilfield. Laboratory experiments and field application prove that the phospho-aluminate cement slurry satisfies the needs for fire soak well cementing.