SP-101 is a medium-molecular-weight, anionic additive that reduces fluid loss in freshwater and seawater muds. It is stable at high temperatures and resistant to bacterial degradation. This synthetic additive stabilizes rheology and minimizes fluid loss in various water-based systems. It works best in low-solids, non-dispersed polymer systems and high-temperature applications. Initial addition may cause a viscosity “hump,” but subsequent treatments reduce it. SP-101 attaches to clay particles, forming a protective colloid on shales and cuttings. It can also deflocculate and stabilize low-solids systems. Recommended treatments range from 0.5 to 1 lb/bbl. Pilot tests are advised before using SP-101.