Modelling the 3D Bit-Rock Interaction Helps Designing Better PDC Bits
The bit-rock interaction has long been studied to assess PDC drill bit performance, which is driven both by cutting and non-cutting parts of the drill bit. While the cutter-rock interaction has been studied by many authors in the literature, only a few studies have focused on the interaction between the rock and non-cutting parts of the drill bit.
In this paper, we introduce a new method designed to model the interaction between the whole drill bit and the rock formation within a full three-dimensional framework. This approach is based on a generic computational geometry algorithm which simulates the drilling process considering both the drill bit and the hole being drilled as a set of 3D meshed surfaces. The volume of rock removed by the PDC cutters as well as the area and the volume of contact between the rock and the non-cutting parts of the drill bit can be computed with a high accuracy based on the 3D CAD model of the drill bit.
The in-house drill bit simulator implementing this algorithm primarily allows the engineer to estimate how bit-rock interactions distribute between cutting and non-cutting parts of the drill bit and to balance the bit design in the 3D space accordingly over a given range of drilling parameters. This approach has been brought to the field in order to address cutter breakage based on rubbing contacts optimization. Field results associated to some case studies in US shale plays and Canada are described and clearly show that contact points predictions closely match field observations. Moreover, design modifications applied following this process have led to an overall increase in bit performance and bit durability while preventing core-out issues.
The bit design methodology presented in this paper is dedicated to design drill bits whose interaction with the rock formation is predicted with a higher accuracy by accounting for the exact 3D shape of the drill bit.