Abstract: Steam flooding is the dominant technology replacing horizontal-well steam soaking in the late development stage of heavy oil reservoirs, and its development effect is impacted by the style of horizontal well pattern.In this paper, the heavy oil reservoir in shallow thin layers in Pai 601 Block, Chunfeng Oilfield was taken as the study object.A high temperature/high pressure 3D scaled physical model was established according to the similarity criteria.Then, physical simulation experiment was carried out on steam flooding in row well pattern, five-spot well pattern and inverted nine-spot well pattern.It is indicated that the growth of temperature field in the process of steam flooding is mainly controlled by the displacement pressure difference between injection well and production well.The injected steam mainly flows to the areas of low flow resistance, such as adjacent well, high permeability belt and high-temperature low-viscosity oil band.In the early stage of steam breakthrough, a large amount of crude oil is still produced from the model.After the experiment ends, there is abundant remaining oil in unswept regions.In the oil reservoir conditions of Pai 601 Block, the ultimate recovery factor of steam flooding in row well pattern, five-spot well pattern and inverted nine-spot well pattern is 45.10%, 41.90% and 38.30%, respectively, and their maximum cumulative oil/steam ratio is 0.69, 0.63 and 0.53, respectively.Based on comprehensive comparison, the effect of row well pattern is the best.The main mechanisms and phenomena in the process of steam flooding include high-temperature viscosity reduction, high-temperature volume expansion, high-temperature steam distillation and crude oil cracking, high sweep efficiency and steam overlapping.The research results provide the effective support for the design of horizontal-well steam flooding in Pai 601 Block, Chunfeng Oilfield.