Abstract
The low rock breaking efficiency of conventional polycrystalline diamond compact (PDC) bits in hard abrasive formations prompts the development of PDC cutting elements from the planar structure to the non-planar structure. As an innovative non-planar cutter, the design and research of the three-ridged diamond element (3-RDE) cutter is still in its infancy, and its rock breaking mechanism and laws are not yet clear. In this paper, a three-dimensional (3D) finite element model of dynamic rock breaking with 3-RDE cutter has been established. The accuracy of the numerical model was verified by experimental data. Then, the difference of rock breaking mechanism between 3-RDE cutter and conventional cutter was studied. The effects of back-rake angle, cutting depth, rotational angle, and rock properties on rock breaking efficiency were also analyzed. The results show that, unlike the conventional PDC shear rock breaking cutter, the 3-RDE cutter breaks rock mainly by crushing and shearing, and the rock breaking efficiency is higher. A small back-rake angle and reasonable cutting depth contribute to improving the rock breaking efficiency; the existence of rotational angle is not conductive to the rock breaking. The field application shows that compared with the conventional cutter, the 3-RDE cutter is easier to penetrate into the formation, and is more stable with less torque required. The research results can be of benefit to the design and manufacture of 3-RDE PDC bits.
Highlights
Polycrystalline diamond compact (PDC) bits are mainly used for drilling soft to medium hard formations
To improve the performance of conventional polycrystalline diamond compact (PDC) bits in deep formations, a series of approaches has been conducted on the material refinement and the design method supplement, such as increasing the number of cutters and blades [7], optimizing diamond packing [8] and using high-temperature and high-pressure (HT/HP) sintering for higher diamond volume in the PDC layer [9,10]
The forces required by the 3-RDE cutter are smaller, process is morecutting stable and efficient
Summary
Polycrystalline diamond compact (PDC) bits are mainly used for drilling soft to medium hard formations. To improve the performance of conventional PDC bits in deep formations, a series of approaches has been conducted on the material refinement and the design method supplement, such as increasing the number of cutters and blades [7], optimizing diamond packing [8] and using high-temperature and high-pressure (HT/HP) sintering for higher diamond volume in the PDC layer [9,10]. Drilling with PDC in hard abrasive formations remains challenging. Conventional PDC bits are still not able to completely substitute the roller cone bits in deep formations
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