Temperature-Stable Polymeric Fluid-Loss Reducer Tolerant to High Electrolyte Contamination

The suitability of a synthetic copolymer for drilling deep, hot wells was demonstrated through laboratory and field testing. The polymer provided fluid-loss control at 400/sup 0/F (204/sup 0/C) to clay-free saturated-salt laboratory muds and to low-solids, nondispersed field muds contaminated with drill solids and sodium and calcium salts. High-temperature/high-pressure (HTHP) filtrate was kept at less than or equal to 15 cm/sup 3//30 min after 400/sup 0/F (204/sup 0/C) heat-aging of a 19-lbm/gal (2277-kg/m/sup 3/) saturated-salt mud. Weighted (> 18-lbm/gal (>2157-kg/m/sup 3/)) potassium muds treated with the polymer showed heat stability and solids and green-cement tolerance. The polymer was successfully field-tested in two offshore wells where bottomhole temperatures (BHT's) reached 400/sup 0/F (204/sup 0/C) and salt and calcium chloride flows were encountered.