Investigation of the Influence of Abrasivity on Drillability of Rocks

Abrasivity, as one of the most important parameters has great influence on drilling rate. Up to now, four known methods such as "Rock Abrasiveness Index (RAI)", "Cerchar Abrasiveness Index (CAI)", "Schimazek's wear factor (F-abrasivity)" and "Bit Wear Index (BWI)" have been developed for evaluating of rock abrasivity. In this paper, abrasivity of six rock types has been studied using Schimazek's wear factor and Rock Abrasiveness Index. For this purpose, equivalent quartz content and the mean size of rock grains have been calculated using thin section of rocks. All types of rocks have been tested view pointed of compressive and tensile strength (Brazilian test) in laboratory. For evaluating of drillability of rocks, the samples have been drilled using actual percussive-rotary drilling machine. Results reveal that by increasing Schmazek's wear factor, drilling rate decreases logarithmically and by increasing Rock Abrasiveness Index, drilling rate decreases exponentially.