Abstract: Surface seawater deep drilling technology is mature in vertical wells and conventional directional wells, and it has been gradually applied to extended reach wells in recent years. How to calculate the depth, build-up rate and deviation of seawater deep drilling, plays an important role in the extended reach well structure, friction torque and borehole cleaning of extended reach wells. Based on the experience of seawater deep drilling in vertical wells and conventional directional wells, perform well surface operations, and combined with the characteristics of extended reach wells, the design and construction of deep seawater extended reach wells are carried out from the aspects of equipment capacity, well trajectory selection, wellbore structure and borehole cleaning.The results show that the surface seawater deep drilling technology is beneficial to improve the aging of extended reach wells and reduce the torque and drag and other parameters. The technology can provide reference for subsequent operation.