Several phenomena that negatively affect drilling efficiency are still commonly observed in practice. These phenomena can often be linked directly to the high torque required for a PDC bit to aggressively shear formation, and the difficulty of effectively transmitting such torque consistently to the bit. In highly transitional or conglomerate formations, the depth of cut and subsequent torque required for the bit to continuously shear formation fluctuates greatly, leading to the buildup and release of torsional energy in the drill string, commonly known as stick/slip. High speeds and vibration during the slip phase, combined with the heterogeneous and/or hard nature of the environment can cause damage to PDC cutters and other drill string components, resulting in reduced bit and tool life as well as poor rate of penetration (ROP). A proprietary torsional impact hammer was tested in applications in Western Oklahoma and in the Southeast Arabian Peninsula where drilling efficiency was believed to be much lower than the theoretical limit. These applications were identified by high cost per foot drilling with roller cone and diamond impregnated bits, as well as known and expected high vibrations accompanying unsuccessful and inconsistent PDC testing. The case studies reveal the strengths and weaknesses of applying such a solution, and introduce a discussion on selection of applications where this solution is advisable. The balance of this paper will also describe how this solution has reduced drilling costs and changed the economics of drilling applications in Western Oklahoma and the Southeastern Arabian Peninsula over the course of the cases studied.

Drilling in the Anadarko Basin in southern Oklahoma can present a number of distinctive challenges including fractured formations, conglomerates and other eccentric geologic phenomena. In this unpredictable drilling environment, it is difficult to optimize/refine the bit/tool and BHA selections, resulting in unacceptable or inconsistent drilling performance. To maximize on-bottom time and cut costs, operator and service-company engineers conducted an in-depth analysis in an attempt to improve section economics. They selected a consistently troublesome application where inconsistencies in the use, performance and dull conditions of bits in close offsets were driving up field development costs. From this group, a specific interval was selected for analysis and the data compared with direct offset runs. In the study, engineers considered bit design/materials, turbodrill and BHA stabilization and drilling parameter optimization. Finally, turbodrill/impreg limitations were considered. The analysis determined that turbodrilling with impregnated bits was a viable option to create savings and could effectively optimize drilling in applications where:specific lithology/formation tops are difficult to define/predictdeviation is caused by hard formations encountered at severe dip angleshigh probability of bit/tool damage from impact/abrasionexcessive fishing/tripping issueshole stability/quality may be compromised by frequent tripsroller-cone and fixed cutter bit performance is inconsistent The new-style turbine/impreg BHA was run with outstanding results. The test interval was successfully drilled, eliminating multiple bit trips and reducing overall days. Cost savings were substantial versus a direct offset well that experienced 38 days of trouble time through the same formations. This trial run gives considerable strength to the hypothesis that impreg/turbine drilling can significantly reduce risk compared to traditional BHAs used in direct offsets. The operator plans to further explore the turbodrill/impreg BHA in the near future. Introduction The Anadarko Basin in Southern Oklahoma is bordered by three major geological uplifts and four major geological basins (see figure A-1). Fracturing, conglomerates, and other geologic phenomena that are associated with these transitions make the drilling environment very problematic. Figure A-2 illustrates some the drilling environment between the Wichita Uplift and Anadarko Basin across the A-A strike plane. Here, overlapping, repeating, and overturned formations, along with extreme dip angles are among the several unique features encountered that make the drilling environment difficult to predict, but also have great potential payouts.

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.

At their advent, PDC bits were aimed at soft formation, fast drilling applications. However, as PDCs have come to dominate market share over roller cones, PDC bit development has shifted focus toward other goals such as durability and longevity which is often in conflict with high ROP. Returning focus to aggressive, high ROP drilling applications has required development of materials, design and manufacturing processes in alignment with that goal set. A cross-functional team was assembled to understand and focus on the high ROP concerns of the end customer and was tasked to develop a PDC bit platform aligned with these goals. This paper discusses general and application specific challenges posed by high ROP drilling applications and how they have been addressed by the aligned development of a new system of materials, design, and manufacturing processes used in PDC drill bits. Formation to bit interaction simulations and computational fluid dynamic modeling analysis are presented in support of the development hypotheses. Field results from case studies and broad field data analysis summarizing the results of extensive testing are presented as well. Driving ROP beyond the ceilings observed in many extreme ROP applications requires that energy be efficiently transferred not just to the bit, but focused on the cutters. To achieve this, an essential change to the base material of the bit body was made, exposing drastically new avenuesand hurdlesfor design and manufacturing. However, the simulation and field results presented confirm that the new system is able to consistently achieve the goal set in high ROP applications.