The double-wall drill pipe reverse circulation converter is a critical component in reverse circulation drilling technology, responsible for switching the flow direction of drilling fluid and transporting rock cuttings. During the reverse circulation drilling process, the drilling fluid carrying cuttings back to the wellhead causes erosion and wear on the converter, which, in severe cases, may lead to complex drilling safety issues. In this study, a finite volume model of the reverse circulation converter was established to systematically investigate its internal flow characteristics and erosion damage mechanisms. The results indicate that the maximum flow velocity and pressure drop in the inner annulus are higher than those in the outer annulus, and significant local throttling effects occur in the diameter-reducing and nozzle channels. Erosion damage is primarily concentrated on the lower inner wall of the converter, particularly in the region opposite the nozzle inlet. This area becomes a structural weak point due to sudden flow path changes, flow direction alterations, and vortex concentration. Sensitivity analysis shows that the erosion rate of the converter increases with drilling fluid flow rate, rate of penetration (ROP), and cutting density, with the sensitivity ranking as follows: drilling fluid flow rate rate of penetration cutting density. Therefore, controlling drilling fluid flow rate, optimizing the rate of penetration, and strengthening protection in high-erosion regions are recommended to improve operational safety and service life. This study provides a theoretical basis for erosion protection and structural optimization of double-wall drill pipe reverse circulation converters.
Wu et al. (Thu,) studied this question.