JOURNAL OF ROCK MECHANICS

JOURNAL OF ROCK MECHANICS

Effect of Bit Size and Geomechanical Properties of Crystalline Marbles on Intrinsic Specific Energy in Rotary Drilling

Document Type : Original Article

Authors
Mohamadreza Rezaeian Foroushani 1
Alireza Baghbanan 2
Keyvan Ebneali Heydari 3
1 M.Sc. in Rock Mechanics Engineering, Isfahan University of Technology, Isfahan, Iran
2 Department of Mining Engineering, Isfahan University of Technology, Isfahan, Iran
3 Ph.D. Student in Rock Mechanics Engineering, Isfahan University of Technology,
10.22034/irsrm.2026.587994.1085
Abstract
Optimizing energy consumption in rotary drilling and reducing associated costs has always been one of the primary concerns of researchers in this field. The present study, employing an analytical model based on the limiting equilibrium of forces and utilizing a drilling rig equipped with a Measurement While Drilling (MWD) system developed by the same research team, calculated the intrinsic specific energy of rock during the drilling process. Based on the theoretical framework, the specific energy of drilling (ε) and the drilling resistance (ζ) are not independent quantities, and a linear relationship exists between them. According to the conducted studies, upon plotting the curves derived from the aforementioned parameters for a fixed-diameter bit under both sharp and dull conditions, an intersection point is observed between the two curves. This point represents the cutting threshold in drilling operations. In this study, the effect of bit diameter — evaluated at three different sizes — on the intrinsic specific energy of drilling was assessed using three marble specimens with varying grain sizes. The findings indicate that intrinsic specific energy is not solely a function of the inherent rock properties, but also depends on drilling parameters. The results demonstrate that with increasing bit diameter, the specific energy of drilling decreased by 20% for Maroon marble, 13.6% for Baghat marble, and 12.5% for Neyriz marble. These results reveal the necessity of reconsidering the assumption that intrinsic specific energy is independent of drilling variables.
Keywords
Rotary Drilling
Intrinsic Specific Energy
Cutter Diameter
Grain Size
Marble
Subjects
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JOURNAL OF ROCK MECHANICS
Volume 10, Issue 1
Spring 2026
Pages 103-118