Evaluation of rotary drilling rate in limestones based on brittleness indices

Accurate estimation of the rotary drilling rate of the rock can save time and cost on exploration operations of the geotechnical projects such as dams, tunnels, oil and gas wells and building stone mines. In this study, the rotary drilling rate in limestone is estimated based on brittleness indices. To achieve this goal, the values of rotary drilling rate, Uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) were determined in three exploratory wells drilled in limestone. Based on the data, the regression relationships of one, two and three variables between rotary drilling rate as a dependent parameter and brittleness indices as an independent parameter were developed. The results suggest that based on one- and two-variable regression relationships, rotary drilling rate can be estimated based on brittleness indices with relatively good accuracy. In addition, the results showed that the three-variable regression relationship was more accurate than the one- and two-variable in estimating the rotary drilling rate. Finally, the three-variable relationship presented in this study could be appropriate in the early stages of exploration operations for geotechnical projects in limestone, which saves time and money.