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2017-10-02 - Colloque/Présentation - communication orale - Anglais - 1 page(s)

Gonze Nicolas , Tshibangu Katshidikaya , "Discrete element modelling of rock cutting experiments under confining pressure" in AfriRock 2017 - ISRM International Symposium 'Rock Mechanics for Africa', Cape Town, Afrique du Sud, 2017

  • Codes CREF : Forages pétroliers (DI2324), Mécanique des roches (DI1418)
  • Unités de recherche UMONS : Génie Minier (F408)
  • Instituts UMONS : Institut de Recherche en Science et Ingénierie des Matériaux (Matériaux)
Texte intégral :

Abstract(s) :

(Anglais) In the future, the oil and gas industry will need to exploit oil reservoirs that are increasingly deeper and difficult to access. With barrel low price, it is essential to improve the whole process of production and, in particular, the drilling operations. To optimize this aspect, it is important to have a good understanding of destruction mechanisms, and more specially in very deep drilling conditions, in a confined environment caused by the pressure of the drilling mud and the ground stresses. This research was particularly focused on the cutting mechanism involved with PDC tools that are increasingly used for the drilling operations. To study the impact of a confined environment on the rock cutting mechanism, we use the Discrete Element Method (DEM) powered by the software PFC2D of Itasca. DEM is more and more used to model rock cutting processes due to its capability to study simultaneously deformation, fracturing and fragmentation. The rock material used in this study is Vosges sandstone. The choice of this rock is explained by the fact that it is regularly used for the study of cutting mechanisms and, that is due to its regular and spherical grains, it is particularly well suited for the DEM modeling. The first step of this work was the calibration of the model. Generally, DEM models are calibrated based on uniaxial compressive behavior of the real material. We ensured that the behavior of the rock is as close as possible to the one observed during triaxial compressive tests. After this first step of calibration, we started the cutting modeling part. Different configurations of confining environment and cutting depths were tested to see the impact of the confining pressure on the cutting forces and on the cutting mechanism. The results obtained show significant differences regarding the ones gathered in atmospheric condition. From the point of view of the cutting mechanism, only one mechanism of destruction was observed in the confined conditions while two, ductile and brittle, were observed in atmospheric condition. We noticed that the only one mechanism is of ductile type with the formation of ribbons of crushed material as was presented in several labs researches (Kaitkay & Lei 2005). In term of forces acting on the cutter we can clearly observe two phases: a first transition phase where the forces increase and a second regime where the forces reach a level and appears to remain constant in average. In future works, it might be interesting to model constant weight on bit to get a better representation of the flow of crushed particles in a real drilling case.