DRILLING FLUIDS

Adverse effects caused by drilled solids account for a major portion of drilling fluid maintenance expenditures. Drilled solids are the number one contaminant of all drilling fluids. Considering that a 12¼ in. gauge hole drilled to 10,000 ft would result in 1,327,000 lb or more of drilled solids, the above statement is not surprising.

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OPTIMUM SOLIDS REMOVAL EQUIPMENT EFFICIENCY

For that reason the resulting solids removal equipment efficiency required is called the optimum solids-removal efficiency. It is independent of the volume of drilled solids reaching the surface, or the volume of the drilling-fluid system. Equating the volume of clean drilling fluid needed to the volume of discard results in the minimum volume of clean drilling fluid needed and, as a consequence, the minimum volume of drilling fluid disposal.

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Centrifuging Drilling Fluids with Costly Liquid Phases

Weighted NAFs present a special problem because of the cost of the base fluid, which can exceed $200/bbl. The objections to series centrifugation raised in the previous section are equally valid for these fluids. Fortunately, NAFs are more solids tolerant than water-based fluids. However, when NAFs are used long enough, ultra-fines and colloids can accumulate to problem levels and force difficult choices.

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