Departure From the Norm in Polycrystalline Diamond Bit Design Allows Significant Performance Gains in Highly Erosive and Abrasive Formations

Abstract

PDC drill bits have grown from niche to mainstream products by gradual, subtle evolutions in design and materials technology. Occasionally, there have been more dramatic step changes in design or materials that have launched PDC bits into new applications. This paper will talk about such a step change: the design, manufacture and application of a contiguous blade of polycrystalline diamond. Rather than blades made up from individual cutters, as with a conventional PDC bit design, this bit has full-length, contiguous polycrystalline diamond coverage, without gaps between cutters on each blade. The advantages of this arrangement are many. Most obvious is the ability to drill erosive and/or abrasive formations without erosion. Often PDC bits, especially lighter set bits, can lose steel or matrix body material between the cutters due to erosion or abrasion, and this can be life-limiting. With no gaps between the cutters, this ceases to be a problem. Other possibilities include: bits for more conventional formations where a contiguous blade can be used instead of backup cutters, enhancing ROP and stability (Maw 2012). This represents a step change in bit design with the potential to redefine bit design across the applications spectrum.This paper details some of the problems with the currently accepted PDC design paradigm, and proposes a novel solution to them by changing it. The hurdles in the way of making the concept a reality and their solutions are described, relating to new concepts in bit design, cutter selection, and new manufacturing process. The testing methodology used to prove the concept in the oil sands in northern Alberta, Canada, as well as the test results are presented. Finally, future planned developments based on the apparent advantages of the invention are forecast. Problem StatementPDC drill bits are obviously composed of two main components: PCD cutters and a body. This is a superficial indicator of all aspects of design and material selection -everything is a compromise. PDC cutters are used to take advantage of the abrasion resistance, hardness, and thermal conductivity of polycrystalline diamond. The bit body, while it is still largely on the same extreme of the material properties spectrum in the grand scheme of all known materials, is comprised of a much tougher mix of components, still at least an order of magnitude softer and less abrasion resistant than diamond. The view has traditionally been that PCD cutters are the most important part of the PDC bit, as they are required to engage the formation and maintain their geometrical properties long enough for shear drilling to be economical. The bit body, then, is necessary only in order to hold the cutters in their arranged layout, and to convey mechanical and hydraulic power to remove the rock in their path.