The following are the main functions of bentonite in drilling: (1) Slurry making: The main purpose of using bentonite in drilling is to make slurry for wall protection. High quality bentonite has a strong slurry making ability and a high slurry yield. (2) Wall protection: The high-quality mud produced by drilling bentonite can penetrate and bond into the easily collapsing sand and stone gaps around the shaft wall, effectively protecting the shaft wall and preventing hole collapse. (3) Cooling the drill bit: When drilling, cutting the drill bit from the sand and rock debris at the bottom of the well can easily generate high temperatures and cause accidents such as burning the drill bit. Bentonite mud is injected from the drill pipe into the gap at the top of the drill bit and continuously pours out mud, which has a good cooling effect on the drill, thereby preventing the burning of the drilling tool and reducing losses. (4) Filtration reduction: Adding a certain proportion of bentonite to the drilling fluid can effectively reduce the water loss of the mud, thereby improving the performance of the drilling fluid. (5) Increasing shear force: Bentonite can significantly increase the viscosity and shear force of drilling mud (6) Stability: Bentonite mud forms a thin mud cake around the well wall, which can reduce the penetration of water in the drilling mud into the well wall, forming an impermeable layer and impermeable wall, preventing borehole expansion during drilling, thereby providing a good protection for the stability of the well wall. (7) Cleaning: High viscosity bentonite mud is driven into the bottom of the well along the holes in the drill pipe, which can remove rock debris from the bottom of the well and keep the bottom clean for a long time. (8) Decompression: The strong lubricity of bentonite can effectively reduce drilling resistance. (9) Collapse control: Due to various reasons, the drilling cannot be completed immediately, and the well wall is prone to collapse due to long-term immersion in groundwater. At this time, high viscosity bentonite mud can be injected into the well to prevent the collapse of the well wall. (10) Sealing slurry: After completion of drilling, it is generally necessary to use bentonite to prepare sealing slurry in sections prone to collapse. (11) Balancing surface pressure: Bentonite mud can balance formation pressure and prevent water inrush and permeability accidents in the well. (12) Preparation of oilfield drilling fluid: Bentonite has good rheological properties and portability in the oilfield, so it can be used to prepare high-performance oilfield drilling fluid, oil-in cement slurry, and high-temperature resistant release agent, effectively improving oilfield drilling speed and reducing the occurrence of drilling construction.