Abstract: The drilling and cementing operations of six extended reach wells in the block QK17-2E of Bohai Bay is described, and the focus is on the casing floating, a key technology for cementing the ?311.15mm hole, which is the displacement section of the extended reach wells. Specifically, casing floating is achieved by combining blind baffle float shoe with floating collar, and using dual-bow centralizers to ensure the centralization of casing and less friction, while roller centralizers are used to reduce the fraction index. A friction prediction software CemSAIDS is used to simulate the real downhole conditions. Double speed drilling fluid displacement technology is applied, to improve displacement efficiency and ensure cementing quality, while return of turbulent and plug flow is achieved. Sea water is used as displacement fluid, which can provide the floating force of casing string. Cementing technology of multi-isolation in single stage in the long open hole is also applied, and it is beneficial for improving the cementing quality of extended reach well on land.