WHITE RESOURCES WATER QUALITY ENHANCEMENT PRODUCTS SOLVE MANY OILFIELD WATER QUALITY PROBLEMS FOR ECONOMICAL COMPLIANCE WITH ENVIRONMENTAL OBLIGATIONS AND REGULATIONS.
Modern oilfield operations must address many environmental and operational considerations for produced water, waterflood and subsurface disposal:
PRODUCED WATER. The quality of produced water discharged overboard from offshore production systems is subject to stringent governmental regulations, as well as corporate philosophies. In U.S. waters and other offshore areas, residual oil and grease levels as low as 29 ppm are stipulated.
WATERFLOOD AND SUBSURFACE DISPOSAL. High quality water enhances reservoir life, helps maintain injectivity and reduces disposal costs for waterflooding operations and subsurface water disposal.
White water clarification products can be divided into two groups. The division is based on whether the chemical is a water based solution or a two phased suspension called a latex. Solution polymers have low to moderately high molecular weights, while latex polymers are extremely high molecular weight vinyl polymers.
WHITE SOLUTION POLYMERS may be a mixture of salts, solvents, and water soluble active ingredients. The active material is often an organic polyamine, but a metallic salt may be used alone. Most water clarification products are solution polymers. These products are easy to make and are easy to use in the field.
• Metal salts are excellent choices for neutralizing zeta potential. Metallic ions with a multiple positive charge are the most efficient. Zinc chloride and aluminum chloride are the most common examples.
• Like metallic salts, polyamines help neutralize zeta potential and speed up the coagulation process. The significant advantages of polyamines are the abundance of positively charged amine sites plus the surfactant and polymer bridging qualities that can be built into the polymer. Polymers with high charge density can be used as alternatives to metals. In filtration applications, highly charged polyamines easily attach themselves to the filter media and still have enough cationic charge potential to help remove oil and solids from the water. Higher molecular weight solution polymers have the ability to help as flocculants through polymer bridging. In all of the polyamines there is a degree of surfactancy not found in metal salts which helps reduce surface tension and increases solids wetting.
• Reverse emulsion breakers are polyamines proven especially useful for resolving oil-in-water emulsion. These products incorporate surface tension reducing properties into the polyamine chemistry and are often blended with metallic salts that speed coagulation.
WHITE LATEX POLYMERS are comprised of three categories; oil external, inverted, and water external.
• OIL EXTERNAL LATEX POLYMERS are made from water soluble monomers, suspended as small droplets within a surrounding organic liquid. Droplet formation is done before polymerization. This permits much larger polymers to be formed within the individual droplets without the problem of long polymer chains forming very thick or solid products. Thus, for polyamines that become more efficient as their molecular weight increases, a latex version of the chemistry is often chosen. Oil external latex polymers can be either anionic or cationic and have molecular weights in the millions. When oil external latex is used, the polymer must be inverted to release the various charged molecules. Inversion is accomplished through the use of surfactants, which disperse the organic liquid and release the water droplets containing the desired chemical. This inversion process requires time and agitation and is sometimes a problem for oilfield applications. However, the added efficiencies obtained with the latex products often make up for the extra effort.
• In some applications INVERTED LATEX POLYMERS are extremely efficient and only very low dosages are needed. Often one quart of chemical can be too much. In order to make these low dosage rates practical from the application standpoint, the latex is actually diluted with water to make a less concentrated product. Of course the polymer inverts in the presence of water and although the product concentration is low, the viscosity is often high. The high viscosity is due to the very high molecular weight of the polymer. Both anionic and cationic latex products can be pre-inverted.
• WATER EXTERNAL LATEX POLYMERS offer an alternative way to make high molecular weight polymers. Water instead of oil is used as the external or continuous phase of the latex process. Water external latex products depend on the use of surfactants to isolate the droplets. When the polymerization process is complete, the surfactants continue to stabilize the droplets and prevent the droplets from coalescing. This technology is less common than external latexes. However, these polymers are easy to pump and disperse quickly in produced water and are often preferred for field applications.
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