Importance

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Abstract

The basic fluid is water, oil or an oil-water mixture. The primary weighting materials are dissolved salts, e.g., sodium chloride, calcium chloride or mixed brines, and in these the calcium or sodium ions inhibit hydration and swelling of drilled solids. When non-cationic fluids are used, an inhibitor is added to prevent such hydration and disintegration--an electrolyte or a cationic surfactant. Any viscosifier added is one having neither a structured viscosity nor gel strength, hydroxyethyl cellulose, for example. When the drilling fluid is pumped to the surface, most of the drilled solids are in their original condition and size and are readily removed and discarded by screening and other available physical means. There is none of the build-up of solids associated with older systems and, hence, no need for discarding, thinning, and make-up.

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First Claim