Experimental study of horizontal casing deformation with different perforation designs under condition of deep shale gas

Deep shale gas has the characteristics of deep reservoirs, including large differences in in-situ stress and complex fracture distribution. During fracturing operation, deep horizontal casing is more prone to damage and deformation than medium-shallow casing. In this study, large-scale true triaxial hydraulic fracturing casing deformation experiments were carried out using three-dimensional optical imaging and scanning to extract the casing deformation information, and the effect of different perforation factors on horizontal casing deformation was studied. The experimental results show that when a certain threshold angle is reached between the perforation direction and direction of maximum horizontal principal stress, shear deformation will occur only at the perforation along one side of the casing, and the deformation will be relatively large. Furthermore, when the perforation direction is parallel to the direction of the maximum horizontal principal stress, shear deformation will occur at the perforations along both sides of the casing, but the deformation will be relatively small. After reducing the distance between perforations, the squeezing forces on both sides of the casing become unbalanced, and the casi­­­­­­­­­­­­­­­ng is more likely to suffer from bending deformation. After reducing the number of perforations, the casing is subjected to greater shear energy at the perforations, resulting in an increase in the shear deformation of the casing. This findings indicate a direction for design and engineering of more robust horizontal casings, thereby contributing to better risk and safety management of deep reservoir hydrocarbon extraction.