The invention relates to a modified
bentonite drilling fluid for
well drilling and a preparation method thereof. According to the preparation method, raw materials containing
bentonite and light modified
powder are subjected to freeze-thaw cycle stirring for multiple times, water loss is carried out at a low temperature, so that the connection strength of molecules in the raw materials is furtherreduced, the light modified
powder and the
bentonite raw materials are mixed more fully after water loss, nanoscale contact is achieved, and the adjusting effect can be improved during tackifying andother adjustment; the
surface charge property of the raw materials can be adjusted by further modifying in a
sunlight exposure or
ultraviolet irradiation manner, so that after a surfactant
tackifier,a flow pattern
regulator, a pH
regulator and the like are added later, the
slurry forming speed is high, the
slurry forming rate is high, the sand wrapping capability is high, the filter loss is low,and the stability is better; the preparation method of the used light modified
powder is a
laser ablation method, no other
raw material is introduced in the preparation process,
metal or
oxide thereofcan be directly ablated to obtain a product, and the light modified powder is high in yield, safe, free of
pollution, free of influence on modification of bentonite and suitable for other industrialapplications.