Synthetic polymers are mainly used at HTHP conditions (>400°F), but there is also an application for them at medium temperatures (250 to 350°F) where generally modified natural polymers, synthetic polymers or combinations can be used. These products support fluid loss control and rheology; however, combinations of different products add cost and complexity to the mud system. These are becoming less robust and often there is a trade-off between good fluid loss control and creation of a negative influence on mud rheology.

This paper details the development of three new fully synthetic, single additive polymers for the medium temperature range. The simplified formulation contributes to a robust drilling fluid combining excellent fluid loss control and low rheology profile. These new co-polymeric materials were designed for the most common WBM drilling applications and can be used in fresh water, in saturated NaCl and different mixed salt brines mainly for filtration control performance and rheological properties. Comprehensive data has been provided on mixed salt brines containing NaCl up to saturation and seawater together with 3% mg/L Mg++, 5% mg/L Ca++ and 6% KCl.

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