Abstract: For easy jamming of the horizontal section of shallow long horizontal well drilling in the western Sichuan region, or sandstone and mudstone interlaced prone to borehole instability and other problems, a novel polyamine imitation oil-based drilling fluid was studied. The drilling fluid is mainly composed of polyamine with strong inhibiting effect and MEG (methyl glucoside) with the primary role of lubrication, lowering filtrate and inhibiting function. The drilling fluid has high lubricating property and strong inhibitory, and the performances of evaluation system approach the level of oil-based drilling fluid. Field application shows that polyamine imitation oil-based drilling fluid has the advantages such as stability performance, a wide range of density regulation, rheological easy to control, small amount of fluid loss and the thin cake, good toughness, effectively inhibiting shale hydration dispersed, and maintaining the borehole wall stable. Thus, the drilling fluid meets the requirements of the long horizontal section construction needs in western Sichuan.