Kneading method for preparing water-based drilling fluid filtrate reducer by using anaerobic fermentation biogas residues

The invention relates to an environmentally friendly filtrate reducer for oilfield drilling fluids, and a preparation method and a use thereof. Raw materials of the filtrate reducer comprise natural polymer mixture biogas residues, an alkalizer, an organic solvent, an etherifying agent, a polysaccharide polymer dispersant and a cross-linking agent. The filtrate reducer prepared through the method has the advantages of good temperature and salt resistance, low price, and environmental protection in the production and use processes, and can be effectively applied in freshwater, brine and composite brine drilling fluid systems.