Laboratory Study on High-performance Lightweight Cement Slurries for Thermal Production Wells

摘要

The main challenging cement slurry problems, such as weak formation with the pressure gradient of about 1.60g/cm~3, non-retrogressive compressive strength at 240°C in steam stimulation and fast compressive strength development at about 18°C in the wellhead, have been encountered in thermal production wells. To answer these challenges, the high-temperature resistant lightweight cement slurries with the densities of 1.40g/cm~3 and 1.50g/cm~3 were designed by choosing density reducer cenosphere and applying the high packing theory. These additives, such as retarder, fluid loss additive and accelerator, were also developed. The rheology, API fluid loss, compressive strength, free water and compressive strength stability in 240°C were researched as well. The result showed that the properties of the cement slurries meet the need of the cementing job at 50°C. The compressive strength on the top of the lightweight cement slurry column was more than 3.5MPa after curing for 36h at 18°C. The compressive strength was more than 30MPa and did not regress after curing for 28d at 240°C. The properties of the high-performance lightweight cement slurries could meet the requirements of the thermal production wells at 240°C.