Basic functions of drilling fluid

（1） Carrying suspending rock debris

Drilling mud additivesThe primary basic function is to carry the rock debris broken by the drill bit to the ground through its own circulation, in order to ensure

Keep the wellbore clean to ensure smooth tripping protect the drill bit constantly contacting breaking new formations at the bottom of the well, avoiding repeated cutting maintaining full speed drilling. When connecting a single pipe, tripping out stopping circulation for some reason, the drilling fluid suspends the drilling cuttings in the well, preventing them sinking quickly preventing the occurrence of sand sinking sticking.

（2） Stable wellbore balanced formation pressureStable wellbore stability wellbore rules are the basic conditions for achieving protection rapid drilling. A drilling fluid with good performance should be able to form a thin tough layer of mud cake on the wellbore through the filtration effect of the liquid phase, in order to stabilize the drilled formation prevent the liquid phase invading the formation, reducing the degree of hydration, expansion, dispersion of shale. At the same time, during the drilling process, it is necessary to continuously adjust the density of the drilling fluid to balance the formation pressure prevent the occurrence of complex downhole situations such as collapse blowout.

（3） Cooling lubricating drill bits tools

During drilling, the drill bit continuously rotates at high temperatures breaks the rock layer, generating a lot of heat. At the same time, the drilling tool also continuously rubs against the wellbore to generate heat. It is through the continuous circulation of drilling fluid that this heat is absorbed in a timely manner then carried to the ground to be released into the atmosphere, thereby cooling the drill bit extending its service life. The presence of drilling fluid causes both the drill bit drilling tool to rotate in the liquid, thereby greatly reducing frictional resistance providing good lubrication.

（4） Transmission of hydrodynamic force

The drilling fluid impacts the bottom of the well at a high flow rate at the nozzle of the drill bit, thereby improving drilling speed rock breaking efficiency. High pressure jet drilling utilizes this principle, which uses high pump pressure drilling to generate a strong impact on the bottom of the well caused by the high-speed jet formed by the drilling fluid, thereby significantly improving the drilling speed. When using a turbodrill to drill, the drilling fluid flows through the turbine blades at a high flow rate the drill pipe, causing the turbine to rotate

Rotate drive the drill bit to break the rock.

However, drilling practice has shown that as a drilling fluid, only achieving the above points is enough. In order to prevent minimize damage to oil gas reservoirs, modern drilling technology also requires the compatibility of drilling fluid with the encountered oil gas reservoirs to meet the requirements of protecting oil gas reservoirs; In order to meet geological requirements, the drilling fluid used is conducive to formation testing does affect the evaluation of the formation; In addition, drilling fluid should also prevent harm pollution to drilling personnel the environment, should corrode downhole tools ground equipment minimize corrosion as much as possible.

In general, the cost of drilling fluid accounts for only 7-10% of the total drilling cost. However, advanced drilling fluid technology can often save drilling time exponentially, thereby significantly reducing drilling costs bringing significant economic benefits.