Drilling fluids: They are sometimes called drilling mud because of their appearance and this is due to the clay that is added to most of them. The benefit of these fluids is to cool and lubricate the drilling head in addition to transporting the drilling products to the surface. The main component of drilling fluids is water.
As for oil-based clay, it can be used at high temperatures and in water-sensitive reservoirs and layers. It is of two types: the first has an external oil emulsion that contains water at a rate of up to 50%, and the second is an oil-based clay that contains a little water.
In general, the deeper the reservoir or well, the more chemicals must be used to maintain the fluid properties.