Research and Application of Low Friction Washing Oil Type Washing Spacer Fluid

Aiming at the cementing problems of high-pressure natural gas wells in Tarim, Sichuan and Chongqing, such as narrow safe density window and difficult displacement of high-density oil-based drilling fluid, according to the suspension, dispersion and flushing mechanism, the key additives such as salt-resistant dispersible fluid loss reducer BCF-Z, salt-resistant and high-temperature suspending agent BCS-Z and high-efficiency flushing agent BCS-T were selected, and a low friction oil washing agent with good stability, excellent rheology and strong oil washing performance was developed. The performance evaluation experiment shows that the highest applicable density of the system can reach 2.4 g/cm3 and the temperature resistance can reach 180 ℃. Excellent rheological property, satisfying n ≥ 0.8 and k ≤ 0.3 pa.sn; Good settling stability at high temperature, and the density difference between upper and lower is not more than 0.03 g/cm3; Good flushing efficiency, more than 95%; The wetting conductivity is high, more than 0.9 S/m; Good compatibility with drilling fluid and cement slurry. This system has been successfully applied in a well in Sichuan and Chongqing, and the cementing quality rate is over 99%, which can effectively solve the contradiction between rheological property and stability of high-density spacer fluid and the difficult problem of oil-based drilling fluid displacement.