Abstract: Reservoir heterogeneity has a significant impact on the development results of well pair by using steam assisted gravity drainage technology (SAGD). Given the complex reservoir conditions, it is difficult to ensure the uniform development of steam chambers, restricting the development result of a single well pair. In view of the low peak production and low recovery factor of a single well during the development process of oil sand project in Mackay River block in Canada due to the strong reservoir heterogeneity,complex geological conditions, as well as limited and uneven development of steam chambers blocked by mud drape layer, an updip multi-lateral well technology is proposed for various pattern types. The well numerical simulation and dynamic analysis are conducted to explore the methods of steam chamber passing through the mud drape layer and condensate oil passing through the mud drape barrier and flowing into the production wellbore after heating, and accurately recognize the development of steam chambers in multi-lateral wells of various well patterns and evaluate their development results. By constructing a mechanism model, four combination schemes of steam injection wells and production wells are designed and the well simulation is conducted based on the field operating parameters to analyze the production performance, remaining oil distribution, steam chamber development, and recovery rate of horizontal section,and summarize the production law of multi-lateral horizontal wells given the complex reservoir conditions; By conducting analysis of well production performance, the SAGD development results of multi-lateral wells are evaluated, and the differences in development results among various well types are compared. The study results show that a multi-lateral well design enables to significantly increase the effective footage, facilitate the dominant pathway for steam injection and oil drainage, improve the steam injection capacity of well pair, increase the swept volume of the steam chamber, and increase the peak oil rate of the well pair, which solves the problem of barrier by mud drape layer to some extent; In actual field production, multi-lateral production well enables to increase the recovery degree of horizontal sections and improve the development results of single well. However, to some extent, it will increase frac-hit and difficulty in well adjustment, leading to an increase in remaining oil in the lower part of the reservoir.