The main target layer of the medium-deep exploration wells in Bozhong area of Bohai Oilfield is the Mesozoic buried hill. The engineering geological conditions in this area are harsh, the pressure system is complex, and the operation risk is high. With the continuous exploration and development in this area, the existing conventional well structures in Bohai Oilfield can no longer meet the requirements of Dobi sealing point isolation and multi-layer testing. It is necessary to carry out exploratory research on non-standard size well structure. First, the geological conditions and three-pressure conditions of this region are explained, the complex conditions of the previous exploratory wells are reviewed, and the design ideas of the well structure are explained based on the actual needs of this operation; then combined with the domestic nonstandard size well structure application precedents and the actual conditions of Bohai Oilfield, three well structure design schemes were proposed. The schemes were compared and selected with the core objective of practicability. The preferred well structure is " Ø609. 6 mm × 240 m + Ø406. 4 mm × 2000 m + Ø298. 5 mm × 3800 m + Ø244. 5 mm ( liner) + Ø177. 8 mm ( liner) ”; finally, the casing strength of the optimal scheme was checked and calculated so as to ensure that the strength requirements under various working conditions during the operation were met. The research results show that the Non-standard well structure proposed in this paper can meet the requirements of exploration well drilling operations and stratification testing in this area. The results of this paper solve the problem of well structure design of exploratory wells under complex geological conditions in the Bozhong region. The research ideas and research results are promising which will serve as an important reference for the future wellbore structure design of medium and deep exploration wells in Bohai Oilfield.