The invention provides environment-friendly water-based
drilling fluid and a preparation method thereof. The water-based
drilling fluid is prepared from the following raw materials in parts by weight: 100 parts of water, 1-5 parts of
bentonite, 0.05-0.4 part of
sodium carbonate, 0.5-3 parts of a filtrate
reducer A, 0.2-3 parts of a filtrate
reducer B, 0.1-1 part of a
viscosity / yield boosting agent, 0.5-4 parts of an inhibitor, 1-5 parts of a
lubricant, 2-6 parts of a micro / nano particle plugging agent and 0-200 parts of weighting materials. The preparation method of the
drilling fluid comprises the steps of adding
bentonite and
sodium carbonate into water; sequentially adding the filtrate
reducer A, the filtrate reducer B, the
viscosity / yield boosting agent, the inhibitor, the
lubricant and the micro / nano particle plugging agent; adjusting the pH value by using
sodium carbonate; selectively adding the weighting materials until the density reaches the drilling requirements. The resisting temperature of the drilling fluid can reach 150 DEG C, EC50 is greater than 3.0*10<4>mg / L, and the drilling fluid is nontoxic and
environmentally friendly and has good rheological property,
filtration reducing property, rejection capability, lubricating property,
pollution resistance and reservoir protection effect.