Abstract: The conventional shale gas reservoir reconstruction process combines casing perforation with multi-stage fracturing reconstruction, with high construction cost and long cycle. With the horizontal well open hole completion, the cost can be reduced and the cycle can be shortened, but the horizontal open hole The stability of the section wall is a prerequisite for the implementation of open hole completion. In this paper, the physicochemical properties and mechanical properties of the Longmaxi Formation shale are studied, and the established open hole completion model is used to evaluate the stability of the open hole wall in the horizontal section of the shale in the Weiyuan-Rongxian area. The results show that the Longmaxi Formation shale is a brittle layered shale with dense rock mass, high mechanical strength and obvious mechanical anisotropy. The oil-based and water-based drilling fluids cause no obvious change to rock swelling performance and mechanical properties. The drilling fluid used in the field has a high compatibility with the formation; the well trajectory, the bedding direction, the mechanical anisotropy, etc. can affect the stability of the open hole section, resulting in a significant difference in the internal stress of the wellbore in different directions; drilling horizontal wells along the direction of minimum horizontal principal stress has the best wall stability. Under the completion condition, the equivalent density of borehole wall collapse pressure is 1.26 g/cm³. In the initial stage of completion, the well wall has a slight collapse, but the collapse range is less than 30°. The horizontal wells can be considered for open hole completion in the Longmaxi Formation shale formation.

Key words: brittle shale, expansion performance, open hole completion, borehole stability