Thermal Response of Polycrystalline Diamond Compact Cutters Under Simulated Downhole Conditions

Abstract

Abstract An analytical method is developed to predict temperatures in polycrystalline diamond compact (PDC) drag cutters under steady-state and transient downhole conditions. The method is used to determine mean wearflat temperatures for cutters under conditions used in previous experiments to measure cutter wear. A correlation between wearflat temperatures and cutter wear rates is demonstrated, and it is shown that, for the particular rock type tested, cutter wear rates increase significantly above 350°C [662°F]. The concept of a critical weight on bit, above which wear-flat temperatures exceed this value, is introduced. The effects of several parameters on the critical WOB are examined. These include cutter thermal conductivity, diamond layer thickness, rock properties, convective cooling, bit balling, and transient events such as bit bounce. Preliminary results of thermal stress modeling show that plastic yielding of the cutter structure can occur under certain downhole conditions.