The Effects of PDC Cutter Geometries to the Drilling Dynamics in Various Geothermal Rocks: A Comprehensive Study Using Advanced Drilling Dynamics Simulation

Abstract

Polycrystalline Diamond Compact (PDC) bit has been used widely in drilling operations since a long time ago. However, the utilization of this bit in Indonesia’s geothermal drilling has just recently started in 2016, thanks to the rapid development of PDC cutter grades and shapes in the last decade. Prior to that, the geothermal drilling operation relied on Tungsten Carbide Insert (TCI) bit to drill the hard formations. The crushing action of the insert bit is very durable to remove the rocks. However, the seal and bearing limit the life of these bit types, causing multiple bit runs in a long drilling section.PDC bit offers longer drilling periods if the cutters are still in good condition. However, the nature of geothermal formation usually consists of hard rocks with fractures that can reduce the durability of the conventional flat PDC cutters. To overcome this weakness and optimize drilling operation,. Instead of having a flat surface, new PDC cutters have different 3D shapes. Each has different benefits: improving cutter strength against impact, increasing aggressiveness and depth of cut, or enhancing wear resistance towards abrasive formations.Advance drilling dynamics simulation helps analyze which cutter types will be more suitable for different geothermal rocks characteristics. The simulation is based on 4D Finite Element Analysis, which models the interaction between the cutting structures and the drilled formation. The result shows the dynamic drilling response of each cutter on different rocks, including the generated vibration, the cutter’s depth of cut distribution on the bit face, and the potential wear pattern on the bit. This paper then discusses which cutter and PDC bit type will be more beneficial for geothermal drilling based on the bit aggressiveness and durability to optimize the drilling operation.