Coagulation is a chemical process by which colloids are destabilized using coagulants. Coagulants reduce the forces that keep suspended particles apart and are used in the cleaning of used drilling fluid along with other processes such as flocculation and dewatering. These processes remove the suspended particles such as drill cuttings, and fluid additives from the water-based drilling fluid.
Drilling fluid is an important part of trenchless methods such as horizontal directional drilling (HDD) as it acts as a lubricant to the drill rod and also helps in bringing the cuttings back to the surface.
Trenchlesspedia Explains Coagulation
Disposal of drilling fluids has become a sensitive issue with environmentalists as it can cause harm to environmentally sensitive natural formations. Drilling fluid can be cleaned and recirculated after treatment instead of being disposed. Drilling fluid consists of finely suspended, dispersed solids or colloids that are stabilized due to electric charges on their surface that cause them to repel each other.
This prevents them from settling which is necessary to keep the fluid from coagulating downhole during trips. Once the drilling fluid is spent, it needs to be cleaned of suspended particles including drill cuttings. This is done by adding chemicals coagulants to the drilling fluid that help aggregation of suspended particles that can be easily removed.
Coagulation neutralizes the repelling charge existing between the particles allowing them to collide and coagulate.