An Optimization Analysis of the Melt-Cutting Diversion Jetting Mechanism for Downhole Drilling Columns

Abstract

Molten metal jet cutting, based on the transient superexothermic characteristics of aluminum thermal reaction, presents a novel technology for swiftly cutting and disposing of stuck drilling columns in downhole oil and gas wells. The key to achieving efficient cutting in drilling columns lies in the jetting mechanism, which guides the high-speed radial ejection of aluminum thermal reaction products that act upon the metal pipe wall. This study uses computational fluid dynamics (CFD) simulation to establish a fluid domain model for the process of cutting molten drilling columns. The optimization of the jetting mechanism is conducted to improve the circumferential coverage by the molten metal by analyzing the impact of molten metal yield and jetting mechanism parameters (cone angle of the conical conductor, diameter, number and length of nozzles, and shape of the diverter). Finally, an ejection test is carried out to verify the optimized jetting mechanism. Research results show that increasing the cone angle of the conical conductor can increase the flow rate of the molten metal at the upper end of the axial nozzle assembly to smoothly discharge the molten metal. Increasing the number of nozzles with equal diameters can increase the circumferential distribution range of molten metal ejected into the cutting area. However, the molten metal circumferential coverage will be impacted by increasing cutting distance. Increasing the nozzle size can reduce the divergence of the molten metal, thereby improving the coverage of the molten metal in the cutting area. When the nozzle arc length L = 8 mm, the molten metal can cover almost the entire cutting area. Adding a 2-mm horizontal draining table at the end of the diverter can assist the molten metal in changing its flow direction, allowing the molten metal to be ejected in a radial direction. The research results provide a theoretical basis for optimizing fusion cutting tools and formulating cutting processes.