The Doseo Depression in Chad is located in the eastern part of the Bongor Basin. It is the main production capacity replacement area for the Chad project. Its Upper Cretaceous and Koumra formations have developed unconsolidated sand layers, which lead to wellbore collapse. During drilling, sand production is severe and difficult to effectively seal, posing risks for the production casing section drilling operation. At the same time, the target layer of Doseo depression has a relatively deep burial depth (average depth of 2800 m), and the production casing section is relatively long. Conventional mechanical liner hanger have problems such as poor sealing performance, and small drift diameter. The hanging weight and overlapping section need to be improved. In response to the above problems faced by downhole operations, the setting principle of the intermediate casing section has been optimized to effectively seal the unconsolidate and unstable sandstone formations in the upper part, creating conditions for reservoir isolation drilling and ensuring safe operations in the reservoir section. At the same time, the expandable liner hanger is used in the production liner, forming a “one well, one strategy” risk exploration well structure optimization technology. It had been successfully applied in K8 wells, which greatly reduced the complexity and nonproduction time due to downhole accidents, and ensured operation safety. It could be widely promoted and applied as a mature technology in the future, supporting the efficient development of the Doseo Depression in Chad. The wellbore structure optimization technology of risk exploration has a demonstration effect on the development of similar oilfields due to its good practical functions and application value.