Study on rock-breaking mechanism of axe-shaped PDC cutter

Abstract

Polycrystalline diamond compact (PDC) cutter is the key component of a drill bit. Recently the shaped PDC cutters, especially the axe-shaped cutter (ASC), have been warmly welcomed by the drilling engineers. However, the rock-breaking mechanism of ASC is rarely studied. In order to investigate the cutting action of ASC, comparative experiments of ASC and conventional cylinder-shaped cutter were carried out based on a vertical turret lathe (VTL). VTL tests' procedure were modified to mimic the initial state, steady state of PDC cutter in the real down hole drilling. The cutting forces and temperature were measured using a dynamometer load cell (3-component force sensor) and a thermocouple, respectively. The results show that ASC has better wear resistance and cutting efficiency than the conventional cylinder-shaped cutter. ASC is easier to press into the rock with its pointed geometry, leading to lower normal force at the initial state of cutting. The cutter shape has large influence on the cutters’ resistance to impact. In addition, both the normal force and tangential force required by ASC during stable cutting are less than that of conventional cylinder-shaped cutter under the same test conditions. Although the cuttings produced by both ASC and conventional cutter have pretty similar particle size distributions, ASC consumes less energy to break the rock based on the fractal analysis of cuttings. • Two states of PDC cutters were simulated on vertical turret lathe. • Consider fractal analysis into cuttings analysis of PDC cutters. • The wear resistance of PDC cutters were compared. • A new experimental attempt to explore the impact resistance of PDC cutters.