INVERT FLUID FLOCCULATION – A Novel Technique for Drilling Fluid Recycling

Solids control equipment at the rig site is used to remove rock cuttings or low-gravity solids (LGS) from drilling fluids to allow the fluid to return to the active system in a re-usable condition. Typical equipment, such as shakers and centrifuges, remove LGS particles greater than 5-7 microns. Build up of finer solids in the fluid can create problems for efficient drilling such as drillpipe sticking, increased drillpipe torque and high viscosity issues. Ultimately the drilling fluid must be diluted and re-formulated to reduce the concentration of LGS and return the fluid to acceptable physical properties. In severe cases, where dilution is uneconomical, the drilling fluid will be disposed as waste. Techniques to remove fine solids from drilling fluids have significant benefits in terms of fluids recycling, inventory control and reducing disposal volume as well as improving drilling performance. With water-based drilling fluids, flocculation of the solids and their subsequent removal using mechanical equipment is commonplace. However, for invert fluids (water-in-oil emulsions) removal of the fine solids has previously been problematic. This paper presents a novel technology for recycling invert fluids with recovery of the re-usable components. Polymeric inverse emulsions and surfactants coupled with defined shear and mixing systems cause the fine solids within the invert drilling fluid to flocculate so they can be removed using standard oilfield centrifuges. The result is the reclamation of the hydrocarbon component with no fine contaminant solids. This component can then be used as a base for new drilling fluids and therefore the treatment provides a unique method for invert fluid recycling. INVERT FLUID FLOCCULATION – A Novel Technique for Drilling Fluid Recycling Karen McCosh Page 2