Changing Selection Concepts: True Optimization of Drill Bits with Latest Generation Rotary Steerable Systems

Abstract

Abstract Use of Rotary Steerable Systems (RSS) has steadily increased since their introduction in the mid-1990's. Improvements in durability, reliability, and operator familiarity, have moved these systems further into mainstream drilling use around the globe. However, the large majority of footage drilled with RSS is with side force (Push) tools. These tend to require some degree of sidecutting, thus utilize drill bits that have specifically engineered cutting structure, profile, and gauge design to achieve this. Due to common availability of this type of bit design, plus extensive experience with operators, they are often also utilized on the growing number of Point RSS. Due to the significant difference in operating mechanism, these bit designs can be poorly suited, resulting in sub-optimal drilling performance. This paper describes a joint engineering approach in developing specific drill bits for the latest generation of RSS that utilizes point-the-bit technology. The project has included systematic testing at a purpose-built, full-size drilling test facility. This has enabled a direct comparison of the directional response, hole quality, and drill string vibration to be made for the various combinations of drill bit and RSS configurations tested. The testing and subsequent field performance has led to development of specified characteristics of the drill bit for optimal performance. To ensure consistent and accurate matching of the bit to this specific RSS, an interactive, intranet tool was developed. This software incorporates logic regarding tool operation and assesses these against key characteristics of the bit including length, profile, gauge geometry, cutting structure, and sidecutting capability. This allows the ideal design to be rapidly identified, particularly as some characteristics are not visible within the visual geometry of the bit. Several case studies are documented that clearly demonstrate that the correct matching of drill bits to this specific Point RSS has delivered improved drilling efficiency with excellent directional control.