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Note: Electrophoretic migration enhances drilling fluid properties and performance and also reduces environmental impact.
DRILLING FLUIDS
Technology using electrophoresis recycles invert-emulsion drilling fluids
Electrophoretic migration enhances drilling fluid properties and performance and also reduces environmental impact.
Karen McCosh, Sarah Wood, M-I SWACO; and Gerry Meeten, Schlumberger Cambridge Research
Applying electrophoresis to drilling fluids aids the removal of solids and brine, positively impacting its physical properties by decreasing the density and viscosity with an increase in the relative oil content. This reduces the excessive dilution that can be associated with reconditioning drilling fluids and effectively extends the drilling fluid's useful life. The waste disposal volumes and associated costs are also reduced. Therefore, this electrophoresis technology meets both operational and environmental goals.
After cuttings and fluids are removed from the borehole, a series of solids-control equipment is used to separate the cuttings from the fluid. The treated fluid is returned to the active drilling fluid system and recirculated back down the borehole.1 Since drilling fluids are used to drill multiple wells, fine (5 [mu]m) Low-Gravity Solids (LGS) build up because they cannot be removed by the separation equipment. Above 2-5% volume, the LGS can generate excessive low- and high-shear-rate viscosities, reduce drilling rates, increase stuck-pipe tendency and increase torque and drag. 2
Drilling fluids are diluted to reduce the LGS concentration and reformulated back to the required properties, which is costly and increases the drilling fluid volume, which leads to storage, transportation and disposal issues. The environmental impact of continuously disposing of large fluid volumes must be addressed and disposal volumes reduced.
This article describes a method for invert-emulsion drilling fluid recycling. The method is based on the principle of electrophoretic movement of charged particles under the influence of an electric field, and is used to remove drilling fluid contaminants, to increase the effective fluid lifespan, and reduce the need for dilution and disposal.
ELECTROPHORESIS
Electrophoresis is the motion of charged, chemically identical molecules in a medium under the influence of an electric field.
The force, F, on a charged particle in an external electric field is proportional to the charge, q, of the particle and the electric field strength, E. This can be represented as:
If q is measured in Coulomb 5 (C) and E is...