Analysis of nozzle for the external casing perforation tool and experimental study on AWJ

Currently, rescue well technology serves as the primary method for control of blowout incidents in land or ocean wells and stands as one of the most critical techniques in well intervention operations. Especially in the case of ocean well blowout accidents, if not dealt with quickly and effectively, it will result in incalculable economic losses and environmental pollution The rescue well technology mainly involves the technical treatment of the external casing perforation in the accident section. However, the operation of external casing perforation downhole is relatively difficult, and the nozzle performance of abrasive water jet(AWJ) casing perforation tools is a key factor in the rescue well technology of the external casing perforation, which directly affects the utilization rate of jet energy, casing perforation efficiency, and tool life. This study adopts a combined approach of CFD simulation and experiment to optimize the diameter of the AWJ nozzle of the casing perforation tool, and the relationship between AWJ nozzle diameter, standoff distance, and flow velocity was determined. Using a high-pressure abrasive jet experimental system, this study systematically investigated the influence of operational parameters on the erosion and external casing perforation efficiency of AWJ tool nozzles. The research results demonstrate that when the nozzle outlet diameter is 5 mm, the conical external casing perforation tool nozzle achieves optimal jet erosion performance while maintaining both high-velocity jet flow and efficient casing perforation capability. Under a jet pressure of 20 MPa, the through-hole diameter of the external casing perforation increases with standoff distance, reaching its maximum value at a dimensionless standoff distance of 8 mm, with the conical AWJ nozzle's maximum effective cutting distance being approximately 120 mm. The minimum jet angle required to penetrate the casing is 10°. As the jet angle increases, the eccentricity distance grows proportionally, with optimal performance achieved at 65°. The through-hole diameter exhibits a linear increase with jet angle, reaching its maximum value at 85°. When the AWJ nozzle spacing is less than 9 mm, interconnected "∞-shaped" perforations can be formed.