FUNCIONES DE LOS ADITIVOS EN LOS FLUIDOS DE PERFORACION
Reductores de calcio. Soda ash, bicarbonate of soda, caustic soda and certain polyphosphates are used to reduce calcium in seawater, treat cement contamination, and overcome contaminating effects of anhydrite and gypsum, both forms of calcium sulfates.
Inhibidores de corrosión. pH control, along with an appropriate corrosion inhibitor, is used to control corrosion, neutralize hazardous acid gases and prevent scale. Common corrosion inhibitors are amine- or phosphate-based products, and other specially formulated chemicals.
Antiespumantes. Products are designed to reduce foaming action, particularly in brackish and saturated saltwater muds.
Emulsificadores. These products create a heterogeneous mixture (emulsion) of two insoluble liquids. They include fatty acids and amine-based chemicals for oil-based muds and detergents; soaps; organic acids; and water-based surfactants for water-based muds. Products may be anionic (negatively charged), non-ionic (neutral) or cationic (positively charged) chemicals, depending on the application.
Reductores de filtrado. Bentonite clays, lignite, CMC (sodium carboxymethylcellulose), polyacrylate and pregelatinized starch all serve to decrease fluid loss, a measure of the tendency of the drilling fluid’s liquid phase to pass through the filter cake into the formation.
Floculantes. These are used to increase viscosity for improved hole cleaning, to increase bentonite yield and to clarify or de-water low-solids fluids. Salt (or brine), hydrated lime, gypsum, soda ash, bicarbonate of soda, sodium tetraphosphate and acrylamide-based polymers may be used. They cause colloidal particles in suspension to group into bunches or “flocs,” causing solids to settle out.
Agentes formadores de espuma. Most often, these are chemicals that also act as surfactants (surface active agents) to foam in the presence of water. These foamers permit air or gas drilling through water-bearing formations.
Hydrate suppressants. These are usually alcohol-based additives, primarily for use in deepwater/coldwater/riser environments.
Recuperador de circulación de materiales. The primary function of a lost circulation additive is to plug the zone of loss back in the formation, away from the borehole face, so that subsequent operations will not result in additional drilling fluid losses. LCM is found in three forms: fiber, flake, and granular/chemical thickening agents, such as ground nut hulls or water swellable, non-soluble, crystalline polymers. In the case of Massive Lost Circulation, two or more of these materials and/or more specialized thickening materials may be needed.
Lubricantes/Agentes liberadores de tubería. Designed to reduce a drilling fluid’s coefficient of friction, lubricants decrease torque and drag. Various oils, synthetic liquids, graphite, surfactants, glycols and glycerin and other chemicals are used for this purpose.
Inhibidores de control de lutitas. Sources of soluble calcium and potassium, as well as inorganic salts and organic compounds, provide shale control by reducing shale hydration. These products are used to prevent excessive wellbore enlargement and heaving or caving while drilling water-sensitive shales.
Agentes activos de superficie. Surfactants, as they are called, reduce interfacial tension between contacting surfaces (water/oil, water/solid, water/air, etc.). These may be emulsifiers, de-emulsifiers, wetting agents, flocculants or deflocculants, depending on the surfaces involved.
Agentes estabilizadores de Temperatura. These products increase rheological and filtration stability of drilling fluids exposed to high temperatures and those that continue to perform their intended purpose under these conditions. Various chemicals are used, including acrylic polymers, sulfonated polymers and copolymers, as well as lignite, lignosulfonate and tannin-based additives.
Disolventes, dispersantes. These chemicals modify the relationship between viscosity and percentage of solids in a drilling mud. They may be used, further, to reduce gel strength, increase a fluid’s “pumpability,” etc. Tannins (quebracho), various polyphosphates, lignite and lignosulfonate materials function as thinners, or as dispersants. Principal purpose of a thinner is to function as a deflocculant to reduce attraction (flocculation) of clay particles, which produces high viscosity and gel strengths.
Viscosificadores. Bentonite, CMC, attapulgite clays and polymers are used to increase viscosity for better hole cleaning and suspension of solids.
Materiales de ponderación. Barite, iron oxides, calcium carbonates and similar products possessing high specific gravity are used to control formation pressures, check formation caving and facilitate pulling dry pipe.