▎ 摘　　要

NOVELTY - High-temperature and salt-resistant fluid loss reducer is obtained by polymerization of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, N-vinylpyrrolidone and dimethyl diallyl ammonium chloride in 1: (2-3.5): (1.5-3): (1.5-3) ratio under the initiator. USE - High-temperature and salt-resistant fluid loss reducer used for preparing high-temperature-resistant high-density saturated brine drilling fluid (claimed). ADVANTAGE - The high-temperature and salt-resistant fluid loss reducer changes the particle size gradation relationship of drilling fluid system, uses saturated brine drilling fluid at high temperature (220 ℃) and high density (2.4g/cm3), and exhibits good rheology and water loss wall-building properties, which can meet the requirements of deep well drilling. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for: (1)a method for preparing the high temperature and salt resistance fluid loss reducer, which involves dissolving 2-acrylamido-2-methylpropanesulfonic acid in deionized water, and adjusting the pH to 6.0-8.0 with sodium hydroxide solution, adding 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, N-vinylpyrrolidone and dimethyl diallyl ammonium chloride in sequence, and stirring for 20-40 minutes, under the protection of nitrogen, raising the temperature of monomer reaction solution to 40-60 °C and reacting for 20-40 minutes, then adding a mixture of sodium bisulfite and ammonium persulfate, and reacting for 4-6 hours to obtain a glue-like produc, repeatedly purifying the product with absolute ethanol and acetone, drying in an oven at 100 °C for 12 hours, and crushing to obtain a high temperature resistant fluid loss reducer for drilling fluid; (2)a high-temperature-resistant high-density saturated brine drilling fluid, which comprises 100 parts by weight of clear water, 3-5 pts. wt. bentonite, 0.1-0.2 pts. wt. sodium carbonate, 0.5-1.5 pts. wt. anti-high temperature and anti-salt fluid loss reducer, 3-5 pts. wt. fluid loss reducer, 3-5 pts. wt. viscosity reducer, 1-2 pts. wt. nano-blocking agent, 0.5-1 part of high-temperature protective agent, 0.5-0.8 pts. wt. sodium hydroxide, 30 pts. wt. sodium chloride, and barite suitable for weighting to the required density; and (3)a method for preparing the high-temperature and salt-resistant saturated water-based drilling fluid, which involves adding bentonite and sodium carbonate to clean water while stirring at speed of 12000 rotations/minute, stirring for 30 minutes, and then maintaining at 25 °C for 24 hours, adding anti-high temperature and anti-salt fluid loss reducer to it, and stirring for 40 minutes, sequentially adding fluid loss reducer, viscosity reducer, nano plugging agent, high temperature protection agent, sodium hydroxide, sodium chloride, and stirring for 60 minutes, and with barite, adjusting the density of drilling fluid to 2.4 g/cm3, and stirring for 60 minutes to obtain high temperature resistant density saturated brine drilling fluid.