Study on the cutting characteristics of different types of abrasive grains on workover bits in the high-temperature environment of the deep wellbore

At present, drilling bits for workover under high-temperature conditions are facing technical bottlenecks such as low work efficiency and rapid wear, especially their working characteristics in the high-temperature environment of the deep wellbore need to be improved urgently. To address this issue, first of all, a two-dimensional orthogonal cutting theoretical mechanical model was established based on Oxley's shear theory to analyze the relationship between cutting parameters and working characteristics. Then geometric models of six commonly used abrasive grains in oil fields, namely disc abrasive grain, cylindrical abrasive grain, honeycomb abrasive grain, long strips of abrasive grain, pointed teeth abrasive grain and prismatic abrasive grain, were established. Also, the thermodynamic coupling simulation models in a high-temperature environment of 180 ℃ were established based on the Johnson-Cook constitutive model. The accuracy of the simulation model was verified through the performance testing equipment of the drilling bit for workover. Single abrasive grain cutting simulation experiments were carried out based on Abaqus, and the cutting characteristics of different structural types of abrasive grains were analyzed from four aspects: cutting mechanism, work safety, work temperature and work efficiency. The analysis results show that: Firstly, the simulation model error of the abrasive grains of the drilling bit for workover is 9.98%, which meets the accuracy requirements for engineering analysis. Secondly, the cutting forces of the honeycomb abrasive grain and the disc abrasive grain are relatively small and have a smooth fluctuation pattern, being 1.27 and 1.45 kN, respectively. Thirdly, during operation, the cutting temperature of the honeycomb abrasive grain is the lowest, at 521 ℃, while the cutting temperature of the prismatic abrasive grain is the highest, reaching 612 ℃. Fourthly, the crushing ratio work of cylindrical abrasive grain is the lowest, at 14.58 J/mm³, while that of prismatic abrasive grain is the highest, reaching 15.54 J/mm³. Based on the analysis of work safety, work temperature and work efficiency, when cutting metal blockages in the high-temperature environment, honeycomb abrasive grain is recommended as the preferred choice. The research content can provide theoretical guidance and technical support for the development of an efficient drilling bit for workover in the high-temperature environment of the deep wellbore.