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2017-06-25 - Colloque/Présentation - poster - Anglais - 1 page(s)

Gonze Nicolas , Tshibangu Katshidikaya , "Correlation between Slab Test and rock cutting modeling using 2D Discrete Element Method" in 51st US Rock Mechanics / Geomechanics Symposium, San Francisco, Etats-Unis, 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)
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Abstract(s) :

(Anglais) During this low prices period for oil and gas on the market, the necessity to optimize drilling operations is more and more present. This optimization goes through a better understanding of the rock destruction mechanism and particularly, of the rock cutting mechanism in the case of PDC drill bits, which are increasingly used in drilling operations. During the last decade, studies trying to provide a solution to this problem have been focusing on numerical modeling, as a more time efficient method compared to laboratory testing or analytical analysis. Among the different numerical methods, Discrete Element Methods (DEM) are commonly used to study the rock cutting process. The main advantage of this numerical method is that it can take into account the granular aspect of rock materials, providing a better understanding of the fracture’s propagation and therefore of the destruction mechanism. The DEM 2D models generally give good qualitative results in term of fractures patterns and chips formation. Unfortunately, the calculated cutting forces using those models are generally lower than the ones measured in laboratory by cutting tests. To be able to compare correctly cutting modeling and cutting laboratory tests, we decided to use a geometric feature of 2D numerical models to conduct our cutting laboratory tests. Indeed, in order to calculate the forces and stresses acting on a cutter in a model, DEM 2D models consider that the sample and the PDC cutter have the same unit width of one meter. Therefore, in order to compare these results, we decided to use the slab cutting tests. The particularity of this test is that the rock sample is prepared in such a way that it has the same width than the rectangular PDC cutter used. The rock material used in this study was 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 due to its regular and spherical grains, it is particularly well suited for the DEM modeling. For the modeling part of this research we took care to model as closely as possible the material both from the standpoint of its mechanical behavior and its grain size distribution. Once the material model is perfectly calibrated (same response to the uniaxial compressive test than the real material) we can initiate the cutting modeling aspect of the study. We highlight the good correlation between laboratory slab tests and the results provided by the numerical models. Indeed, the evolution of cutting forces depending on the depth of cut is comparable to laboratory tests and they are quite comparable in terms of magnitude. These results show that the discrete elements numerical models in two dimensions can be used to obtain a correct estimation of cutting forces and therefore, to quickly study different geometries of rectangular PDC cutters. Despite these good results, it still remains necessary to go through laboratory and 3D modeling tests for other cutter geometries.