Due to the necessity to exploit deeper petroleum reservoirs and to uncertainty about the oil price, the oil and gas industry needs to optimize all process costs, and in particular, drilling costs. This requires a better understanding of rock cutting mechanisms in a confined environment, as encountered in deep drilling conditions. In this paper, we focus on the specific cutting mechanism exhibited by polycrystalline diamond compact (PDC) drill-bits. To study the effect of the confining pressure on the rock-cutting mechanism, we use the discrete element method powered by PFC2D software from Itasca. We firstly develop a new approach to calibrate the discrete element model. Unlike the usual method based on considering the mechanical behaviour of the rock under uniaxial conditions, our method considers the behaviour during triaxial compressive tests. We present the results of our numerical simulations of rock-cutting tests with different configurations of confining pressure and cutting depth. We highlight significant differences, in terms of cutting mechanisms and forces acting on the PDC cutter, between results obtained under confining pressure and results gathered in ambient conditions. Finally, we compare the numerical simulation outputs with some laboratory results from the literature, and show a good correlation between the two methods.
The oil and gas industry needs to exploit increasingly deep oil reservoirs that are difficult to access. With the current low oil price, it is essential to optimize the whole process of production to limit costs and, in particular, the expensive drilling operations which are a major contributor to overall expenditures. The optimization of drilling operations requires a good understanding of the rock-cutting mechanisms during drilling. The cutting mechanisms have generally been well studied in ambient conditions, but the effect of the confining pressure in deep drilling conditions is still not well understood.
In this research, we focus more specifically on the cutting mechanisms of polycrystalline diamond compact (PDC) drill-bits. The choice of PDC bits featuring multiple PDC cutters on the bit face is justified by their increasing use in drilling operations due to their superior mechanical properties.
