According to its function, drilling fluid has

1) Weighting agent

When the fluid column pressure of the drilling fluid cannot balance the formation pressure a blowout needs to be killed, it is necessary to add weighting agent to the system to increase the specific gravity of the drilling fluid to balance the formation pressure prevent blowout accidents. The commonly used weighting agent is Baryte (BaSO4)

2) Fluid loss agent

In order to reduce the filtration of drilling fluid into the formation ensure the wellbore, the chemical agent used to protect the stability of the mud colloid is called a fluid loss agent.

The commonly used filter loss agents currently include:

Carboxymethyl cellulose, hydroxyethyl cellulose, modified starch, etc. These products can be dispersed in water but dissolved to block pores in the formation, prevent filtration, because they are oil soluble, they will block oil gas channels. At the same time, they can also be used in completion fluids, workover fluids, perforation fluids.

3) Dispersant (also known as diluent)

When the clay drilling cuttings in the drilling fluid reach a certain concentration, a spatial network structure will be formed. When drilling into a salt gypsum layer, the dissolved salts in the formation water, especially high valent cations, will exacerbate the formation of the network structure, resulting in poor fluidity of the drilling fluid. An additive that can break down this network structure, release free water, reduce the viscosity shear force of drilling fluid is called a dispersant. Commonly used dispersants include lignin sulfonates their complexes with iron chromium, titanium, manganese, tin ions.