Nanometer titanium dioxide blocking agent, water-based drilling fluid and preparation method of water-based drilling fluid

The invention belongs to the field of drilling fluids, and particularly relates to a nano titanium dioxide blocking agent, a water-based drilling fluid and a preparation method of the water-based drilling fluid. Raw materials of the blocking agent comprise butyl titanate and graphene, and the particle size of the blocking agent is 10-20 nm. The raw materials of the water-based drilling fluid comprise the following components: water, bentonite, KCl, sodium carbonate, a filtrate reducer, an inhibitor, a blocking agent, a tackifier and a weighting agent. The preparation method comprises the following steps: sequentially adding the bentonite, the KCl, the sodium carbonate, the filtrate reducer, the inhibitor, the blocking agent, the tackifier and the weighting agent into water, and stirring. The nano titanium dioxide plugging agent prepared by the method can be well dispersed into the drilling fluid, and has small influence on the viscosity and shearing force of the drilling fluid. The plugging agent can be used