Biopolymer for drilling fluid and preparation method thereof

The invention belongs to the technical field of oil exploitation, and particularly relates to a biopolymer for drilling fluid and a preparation method of the biopolymer. The preparation method comprises the following steps: sequentially adding lauryl amine dipropylidene diamine, ethanol and sodium chloroacetate into a reactor, adjusting the pH value, carrying out a heating reflux reaction, cooling to 40 DEG C or below, adding epoxy halopropane, and carrying out a heating reflux reaction; and adding xanthan gum, an ethanol solution and a sodium hydroxide solution into another reactor, stirring for swelling, adding the mixed solution, heating for reaction, adjusting the pH value to 7-8 by using hydrochloric acid, cooling to room temperature, centrifuging, washing, filtering, drying and crushing to obtain the product biopolymer. The invention has the advantages of wide raw material source, simple synthesis process, no pollution, high apparent viscosity, good antibacterial property and filtrate loss reduction pro