Abstract: Recently salt gypsum beds and brine water layers are frequently encountered when drilling deep wells.The conventional spacer system has a relatively poor salt and temperature tolerance.When the temperature exceeds 100℃,the system loses its stability in the low concentration of saline water and can cause serious cementing accidents and has a great potential safety hazard of injection and displacement of slurry.A polysaccharide polymer is chosen as high temperature and anti salt suspension stabilizer,and supplemented by salt tolerant fluid loss additive and pattern adjusting agent,a high temperature and anti salt spacer system is developed.The system could maintain its stability in the sodium,calcium and magnesium salt solution.It can be used in a temperature of 140℃ and has a preferable regulation ability of density which can be adjusted between 1.3 and 2.4g/cm3.It also has a good compatibility with conventional drilling fluid and cement slurry.The system is expected to be used in cementing job of the deepwell,high deep well,and salt gypsum bed,composite rock salt layer,and brine water layer.

Key words: spacer fluid, high temperature, salt tolerance, salt gypsum bed, brine water layers, cementing quality