Design Techniques for Reducing Toughness Related Cutter Issues in Carbonate Formations

Abstract

Carbonate formation drilling with PDC drill bits often leads to accelerated catastrophic diamond table loss of the PDC cutter. Historically, PDC toughness related failures have been blamed on the bit/formation interaction producing destructive drilling dysfunctions such as; axial, lateral, and torsional vibrations. A number of design techniques have been applied to cutting structure/bit body design in an attempt to reduce the intensity and frequency of bit/formation interaction related drilling dysfunctions. These techniques were successful in reducing bit/formation interaction instigated drilling dysfunctions, however accelerated catastrophic diamond table failures were still observed at historical rates. This has led to the hypothesis that the accelerated catastrophic diamond table loss observed in carbonate formations is not exclusively related to drilling dysfunctions. The aforementioned hypothesis initiated a detailed study focusing on the relationship between cutting structure design and the damage observed from drilling carbonate formations. The results of this study clearly identified a relationship between hydraulic configuration, the relative magnitude and orientation of individual cutter’s impact force, and observed catastrophic diamond table failure. Several experimental PDC drill bit designs were constructed using different hydraulic and cutting structure design techniques. These techniques were aimed at reducing the hydraulic erosion potential of cutter substrates and normalizing forces across the majority of the cutting structure. The product of these experimental bit runs has been incredibly positive. In every case, the optimized hydraulic configuration and impact force normalized cutting structure design has outperformed the control designs while drilling carbonate intervals. This paper will focus on the performance differences between several control and experimental fixed cutter designs operating in the Anadarko Basin. The salient differences between these designs are the hydraulic configurations and the orientations of individual cutters on the control and experimental cutting structures. The slight modification of hydraulic configuration and individual cutter orientations (from control to experimental) has produced remarkable improvements in efficiency and durability. Several 7 7/8" diameter bit designs will provide the technical basis for this paper.

Avaliação Numérica Do Processo Mecânico De Corte Em Evaporitos E Carbonatos Através Do Método Dos Elementos Discretos

“…Sun et al (2000) A agressividade da broca pode ser definida como sendo uma resposta da broca em termos de velocidade axial à uma força axial aplicada (peso sobre a broca -WOB) e à uma rotação (revoluções por minuto -RPM) em um ambiente idealizado. A agressividade pode ser influenciada por diversos fatores, entre eles: ângulos de inclinação lateral e de ataque dos cortadores, espaçamento dos cortadores e exposição do cortador à rocha (Weeden and Whipple, 2010). Hinaai et al (2013) também apresentam estudos relacionados a projetos de broca PDC para fins de ganho de performance em ambientes complexos como em reservatórios de carbonatos.…”