The problem of casing deformation caused by large-scale hydraulic fracturing in shale oil wells severely restricts the efficient development of Gulong shale oil. In order to clarify the mechanism of casing deformation in shale oil wells, comprehensive analysis was conducted on engineering factors, multi-arm caliper logging, seismic attributes, and the distribution characteristics of casing deformations. This study shows that casing strength, cementing quality, and wellbore curvature are not the main controlling factors for casing deformation. Casing deformation is caused by the communication between hydraulic fractures and natural fractures during the fracturing process, which increases the fluid pressure in the natural fracture and induces shear slip, resulting in casing deformation due to shear stress. Based on the understanding of the mechanism of casing deformation in shale oil wells, two targeted casing deformation prevention and control methods are proposed. First, temporary plugging was implemented during the hydraulic fracturing process when the fluid volume reached 1000 m³, and the pumping rate was reduced to below 16 m³/min to reduce the internal fluid pressure of the fractures and control fracture slip, thereby minimizing the risk of casing deformation. Second, hollow particles were added to the cement to enhance the consolidation effect of the cement sheath and mitigate casing deformation caused by fracture slip. Research indicates that a hollow particle content of 15% can meet the requirements for casing deformation control in Gulong shale oil. These research results can provide important references for the prediction and prevention of casing deformation risks in shale oil and similar unconventional reservoirs during hydraulic fracturing.

Vortex drainage gas recovery has been used to carry liquid from gas wells. However, the traditional vortex tools in gas wells cannot produce long effective distance spiral flow at a low gas flow rate, and their operating mechanism has not been thoroughly analyzed. In this paper, the venturi acceleration vortex tool for a horizontal gas well is designed to improve drainage performance. The tube drainage, the vortex tool, and the venturi accelerated vortex tool were applied in a horizontal tube to investigate their drainage capacities by a horizontal well multiphase flow experimental device. The influence of different gas flow rates and liquid flow rates on the length of the spiral flow and pressure drop produced by the three tools was analyzed. The results show that the vortex tool can convert the gas–liquid mixing flow into the gas–liquid separation flow, that is, the liquid flows spirally along the wall and the gas flows in the center of the horizontal tube. Compared with the vortex tool, the venturi accelerated vortex tool can form a longer and more stable spiral flow. The laminar spiral flow reduces the total pressure drop in the tube. The length of the spiral flow increases with the increase in the gas flow rate. With the increase in the liquid flow rate, the spiral flow is not clear because of the turbulent flow. The length of the spiral flow and the pressure drop for the venturi accelerated vortex tool with different gas and liquid flow rates are analyzed to guide the application of the tool. This study provides a new means for the drainage of a horizontal gas well and further clarifies the working mechanism of the vortex drainage tool.