An experimental and numerical study on the wear mechanism of cutters on workover bits under thermo-mechanical coupling

Abstract

The workover bit is the core tool for removing mental junk in the wellbore and determining construction efficiency. In order to solve technical bottlenecks of slow footage and fast wear, a thermo-mechanical coupling analytical model of cutter on workover bit was proposed based on the principle of the heat source method, which clarified the quantitative relationship between temperature, structure, and physical parameters. Also, a thermo-mechanical coupling 3D numerical model of cutter was proposed by the penetration contact algorithm of temperature-displacement coupling, which revealed the chip formation mechanism and distribution characteristics of high-temperature areas. Besides, as the severe conditions of insufficient cooling of workover bits, the non-cooling milling experiment of the workover bit with single cutter was carried out. Then the wear morphology characteristics and wear mechanism under the action of thermo-mechanical coupling were explored. The results show that the temperature error of the thermo-mechanical coupling numerical model of cutter is within 13.0%, which meets the accuracy requirements of basic engineering analysis. Under the action of thermo-mechanical coupling, the workover bit produces roll-shaped chips with a curvature radius of 2.03 mm. The high-temperature area of cutter is distributed on the outside of the cutting edge. In the meanwhile, the temperature on the rake face of cutters has the fastest increase and the highest temperature, and the highest temperature can reach 541.6 °C. The wear mechanism of cutter can be divided into four stages: gradual indentation stage, mechanical wear stage, bond wear stage, and high-temperature oxidation stage. When milling continuously for 5 min, the wear volume of the cutter reaches 0.51 mm3, and controlling temperature is the key to reducing the wear of the cutter. This research can provide theoretical guidance and a scientific basis for revealing the wear mechanism and prolonging the service life of workover bits.