Abstract: To address the challenge of “collapse induced by lost circulation” during the development of tight gas reservoirs in the northern Ordos Basin, caused by the development of microfractures (width: 10–100 μm) and high clay mineral content (illite/smectite mixed layer > 40%), an analysis of the physical properties and microscopic physicochemical characteristics of formation rock samples was conducted. It was revealed that the high clay mineral content and the development of microfractures were the main controlling factors for wellbore instability. Based on the main controlling factors of wellbore instability, a technical strategy of “rigid-flexible synergistic instantaneous plugging combined with long-term clay inhibition” was proposed. By optimizing the dosages of multi-stage micron-sized rigid material XNZY and nano-flexible plugging agent XNEX and selecting appropriate inhibitors and fluid loss reducers, an instantaneous plugging water-based drilling fluid centered on multi-stage rigid plugging materials and nano-flexible plugging agents was developed. The performance of the instantaneous plugging water-based drilling fluid was evaluated in the laboratory. The drilling fluid rapidly formed a plugging layer, achieving a pressure-bearing capacity of 10.6 MPa, a cuttings rolling recovery rate increasing to 85%, and a hydration swelling rate reducing to 52.1%. During drilling through the Liujiagou Formation in Well A, the instantaneous plugging water-based drilling fluid was tested. Compared with Well B on the same platform, which used conventional drilling fluid, the drilling fluid loss volume was reduced by 69.7%; the well diameter enlargement rate in the same interval decreased from 7.61% to 4.52%, and no downhole complications occurred. Research and field tests have shown that the instantaneous plugging water-based drilling fluid, through rigid-flexible synergistic plugging and efficient inhibition, resolves the vicious cycle of “lost circulation, hydration, and collapse” in fractured formations, providing reliable support for safe and efficient drilling in the northern Ordos Basin.