Abstract: The influence of potassium chloride and potassium silicate on the rheology and filtration of drilling fluids has been studied.The formulation of the potassium silicate mud system has been established, that is 4% bentonite mud +3% potassium silicate+0.5% JT888-Ⅲ+3% FDJ-1 + 2% QS-2 + 2% TY540 +3% SMP-Ⅱ. Results indicate that the potassium silicate mud system has good properties on rheology, filtration and inhibi-tion, and is better than the potassium chloride mud system at the same dosage. Meanwhile, it has good thermal stability (120℃) and anti-contaminative ability(5% NaCl, 0.7% CaSO4).

Key words: potassium silicate mud, inhibition, thermal stability, anti-contaminative ability