Single PDC Cutter Studies of Fluid Heat Transfer and Cutter Thermal Mortality in Drilling Fluid

Many PDC cutters ‘die’ of overheating. Improving thermal resistance improves cutter performance, thereby extending bit life. Development of heat resistant cutters requires a test method that emulates heat transfer as it occurs during drilling. One method of testing cutters is to use a single cutter to cut granite. Single cutter studies eliminate many uncontrollable variables found in full bit studies, and allow for direct measurement of cutter performance. Typically, these include evolution of heat, measured as temperature, and the measurement of wear flats as a function of cutting time. However, in some cases there are significant differences between cutter performance observed in the tester and in the field. We have found that using viscosified drilling fluid instead of water provides a thermal environment that significantly improves the correlation between lab and drill site performance.