Temperature-resistant and salt-resistant filtrate reducer multi-branched resin for drilling fluid and preparation method of temperature-resistant and salt-resistant filtrate reducer multi-branched resin

The preparation method comprises the following steps: firstly, adding 2000-2500 parts of water into a reaction kettle, adding 1200-1500 parts of humic acid while stirring, then adding 100-150 parts of sodium hydroxide, heating to 75-80 DEG C, reacting for 50-70 minutes, carrying out precipitation separation on the obtained liquid, removing settled residues, adding 100-200 parts of hydrolyzed polyacrylonitrile salt while stirring, heating to 75-80 DEG C, reacting for 50-70 minutes, filtering, washing, and drying to obtain the temperature-resistant salt-resistant filtrate reducer multi-branched resin for drilling fluid. Then adding 36-60 parts of sodium pyrosulfite, 40-70 parts of AMPS, 30-50 parts of formaldehyde and 15-30 parts of high-temperature defoaming oil, carrying out stirring reaction at 120-125 DEG C for 180 minutes, and drying the obtained liquid to obtain the water-based paint. The temperature-resistant salt-resistant filtrate reducer multi-branched resin for the drilling fluid has the advantages o