Abstract: Drilling operations have set an increasingly higher requirements on heat resisting capacity of drilling
fluids， and the conventional drilling fluid systems could not well met the requirements of the deep or ultra-deep
well drilling. based on calcium humate heat resisting mechanism， the experiments and ways of evaluation including
drilling fluids in high temperature rolling， rheological characteristics， and fluid loss property are carried out， and
the performance of drilling fluid system which could be influenced by different CaO and increasing bentonite is
comparatively analyzed. Anti-high heat fluid loss additives such as CMC， SMP， FV-2 are optimally screened， and
a series of calcium humate drilling fluid system with anti-high heat（180℃）and anti-salt（30% ）is raised. The
results show that the optimal base fluid contains 0.3%CaO， 7%SMC and 5% bentonite， while the optimal calcium
humate drilling fluid system contains 7% SMC， 0.5% CaO， 5% bentonite， 5% SMP-1 and 0.3% FV-2， which has
an excellent resistance to high heat of 180℃ and high salinity of 30%.

Key words: calcium humate, drilling fluid, anti-high temperature, anti-high salinity, deep well