Solid-free drilling fluid prepared from oilfield production wastewater and preparation method of solid-free drilling fluid

The invention provides a solid-free drilling fluid prepared by utilizing oilfield production wastewater and a preparation method thereof, core treating agents of the solid-free drilling fluid are a tackifier and a filtrate reducer, and amide groups and sulfonic acid groups are respectively introduced on fenugreek gum and starch and are used as the tackifier and the filtrate reducer of the oilfield water solid-free drilling fluid. The two groups have good salt resistance, and particularly the sulfonic acid group can form a strong solvation layer on a macromolecular chain link, so that the salt-resistant, temperature-resistant and pollution-resistant effects are achieved, a stable grid structure is formed in oil field production wastewater, and the effects of tackifying and filtrate loss reducing are achieved; the oil field water solid-free drilling fluid prepared from the oil field water solid-free drilling fluid has good rheological property, temperature resistance and reservoir protection performance, and ca