Abstract:

Silicate-based drilling fluids with main additives being sodium or potassium silicate have been widely applied in recent years. The system shows strong borehole stability and environmental compatibility. Its stability mechanism differs from other water-based drilling fluids. After introducing the system, the borehole stability mechanism this paper is particularly analyzed .There are four aspects contributing the mechanism: (1) quickly plug pores and fractures near - wellbore, stop filtrate from entering formation and reduce pore pressure penetration; (2) constrain hydration of clay minerals in shale; (3) silicate reacts with clay minerals; (4)coordinate stability of other inorganic salts.

Key words: Drilling fluid, Silicate mineral, Hole stabilization, Mechanism, Shale