Case Study: Drilling at the Cutting Edge of Performance With Shaped-Cutter Technology

Abstract

_ Shaped cutters are not new to the industry. They were introduced decades ago when drilling environments began to change and more complex formations introduced new challenges, and they have been part of drill-bit technology portfolios since the 1990s. For many years, development teams have been investigating downhole conditions that were causing cutter damage and drilling dysfunctions, continually playing with the balance between materials and geometry. That knowledge has been a springboard for focused R&D efforts to improve cutter designs to contend with demanding drilling conditions and more complex wellbores. Today, shaped cutters push performance to new limits in applications that traverse multiple formations on a single run, from interbedded, to hard rock and abrasive formations, through sand, clay, sandstone, and limestone. Developing Shaped-Cutter Technology An entire suite of shaped cutters (Fig. 1) has been developed using the latest in materials research to address a range of challenging formation types and applications. Drilling engineers can place combinations of specialized cutters on a single bit to drill efficiently through complex formations. One of the advanced cutters (Fig. 1a) that emerged from these development efforts is a design that improves performance in hard formations. The resulting cutter has novel edge geometry to stand up to high-impact loads and a secondary chamfer on the diamond face that enables it to withstand higher loads than polycrystalline diamond compact (PDC) cutters. This allows it to maintain drilling efficiency in hard, interbedded formations, leading to a higher overall rate of penetration (ROP) for the interval. When drilling in hard, abrasive formations, heat generated from the rock-cutter interaction can break down the integrity of the cutter, leading to premature wear and reduced performance. Engineers focused on enhancing the improved cutter tip to develop a cutter (Fig. 1b) that remains cool in hard, abrasive formations and is particularly effective in sandstone, where it exhibits considerably less microfracturing and wear than traditional cutters. Complex runs often mean that bits must drill through very different formations, from interbedded, hard rock to more abrasive formations. To contend with these varying conditions, a cutter must be effective in high-impact loading conditions and still be functional at end of run. Another specialized cutter (Fig. 1c) was developed to deliver this balanced performance, reducing friction and heat generation at cutter/rock interface, breaking up rock cuttings, and enabling faster drilling and longer runs with a lower weight on bit (WOB) requirement for a given ROP. Conditions where point loading is required, such as drilling through evaporites or high-mud-weight environments and in drilling runs where WOB is limited, require a cutter with the ability to distribute more weight to a smaller portion of the rock. Baker Hughes designed a cutter (Fig. 1d) for these conditions that penetrates the formation more effectively than standard cutters by generating a larger depth of cut using the energy available to deliver faster drilling runs. The most recent addition (Fig. 1e) to the specialized cutter portfolio takes on even more demanding conditions with a design that delivers greater durability with the inclusion of secondary chamfering, a relief in the center of the cutter, and enhanced point-loading capability.