4. Cooling and lubrication
When drilling, the drill bit has been rotating and breaking rock strata at high temperature, producing a lot of heat; the drilling tool also continuously friction with the shaft wall to produce heat. Through the circulation of drilling fluid, the heat is taken away in time, which can play the role of cooling bit, drilling tool and prolonging its service life. Because of the existence of drilling fluid, the drill bit and drilling tool are rotated in the liquid, so the friction resistance is greatly reduced, which plays a good lubricating role.
5. Transfer of hydrodynamics
The drilling fluid is ejected at a very high flow rate at the drill nozzle, and the high speed jet produced a strong impact on the bottom of the well, thus improving the drilling speed and rock breaking efficiency. High pressure jet drilling is to use this principle, significantly improve the mechanical drilling speed. When drilling with turbine drilling tools, the drilling fluid flows through the turbine blade at a higher flow rate from the drill pipe, making the turbine rotate and driving the bit to break the rock.
6. Access to underground information
Through the change of rock debris and drilling fluid performance to obtain all kinds of underground information for drilling construction to provide the basis for the formulation of technical measures.
In addition, in order to prevent and minimize damage to oil and gas reservoirs, modern drilling technology also requires that drilling fluid must be compatible with the oil and gas reservoirs encountered by drilling to meet the requirements of protecting Shantou gas reservoirs; in order to meet geological requirements, the drilling fluid used must be conducive to formation testing without affecting formation evaluation; drilling fluid should also be free from injury and pollution to drilling personnel and the environment, small corrosion to downhole tools and surface equipment or minimize corrosion.
Generally, the drilling fluid cost only accounts for 7%~10% of the total drilling cost. However, the advanced drilling fluid technology can often save drilling time twice, thus greatly reducing the drilling cost and bringing considerable economic benefits.