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. Introduction The paper focuses on the development and testing of one of the latest generation point-the-bit RSS. The tool comprises three main elements; downhole electronic control module, mechanical bias unit and pivot stabilizer (Figure 1). The bias unit is a hydraulic/mechanical mechanism that develops power from differential rotation between the rotating drill-string and a nonrotating steering sleeve. This hydraulic power is used to deflect the drill-string (eccentrically to the borehole) in the required direction for steering. The system employs a pivot (fulcrum) stabilizer such that the driveshaft is deflected in the opposite direction to required hole deviation (Figure 2). Sprung anti-rotation guides prevent the steering sleeve from rotating, but if the sleeve begins to roll, the system automatically redirects hydraulics to maintain desired orientation. The electronic control module applies algorithms to provide closed loop control of the position of the bias unit, giving tight toolface control and proportional deflection control; enabling fine adjustment of wellbore deviation rates.

Development and diversification of directional drilling tools continues, as do the applications in which they operate. As a result, there is continual demand for development and refinement of drill bits and string tools to meet the latest challenges and issues faced. One such challenge is the ability to reliably deliver consistent directional performance in very soft formation applications. Issues such as hole washout, inappropriate drilling parameters, stabilization, and hole quality can all contribute to poor directional drilling performance. Several commercial projects are reviewed where technical merit has justified use of Rotary Steerable Systems (RSS), but due to the very soft lithologies, these systems have been unable to deliver the required directional control. In each example, a separate engineered solution is introduced. These include:An innovative concentric string reamer, featuring a mid-reamer section that enables effective stabilization of the reamer even if the pilot borehole is of poor quality or is over gaugeA soft formation fixed cutter drill bit design with an engineered hydraulic configuration to avoid hole washout and extended circumferential gauge geometryA near-bit stabilizer incorporating a full ring gauge that delivers 360 degree circumferential coverage, thus providing greater contact with the wellbore and higher potential for deviationA specific Bi-center design that utilizes a secondary component configuration on the face of the pilot to enable appropriate drilling parameters to be utilized for efficient directional control. The gauge geometry and profile is also tailored to suit soft formation drilling. Global case studies document where these solutions, in combination with both Push and Point RSS, have proven extremely successful. These have provided greater flexibility with regard to tool selection, well planning options, and delivering lower cost per foot in RS projects. Introduction Approximately 60 to 80%1 of the formations drilled in the oil and gas industry are shale or shaly type formations which are mechanically weak and easily penetrated. These present multiple drilling challenges. From a drill bit perspective, designs are developed in order to overcome the potential of bit balling, a scenario where formation cuttings pack together and stick to the bit face, resulting in reduced drilling efficiency. Solutions may include optimizing the open face volume, though potentially at the cost of reduced durability of the designs. Generally, steel bodied bits are considered optimal in this environment as they typically have higher blade standoff and thinner blades when compared to that of a matrix bodied design. This affords them an increased open face volume and larger junk slot area. Matrix bodied bits are composed of an infiltrated matrix of tungsten carbide powder, offering excellent surface hardness properties with an exceptional ability to resist fluid erosion, significantly higher than their steel bodied counterparts. This is beneficial as flow rates utilized in soft formation tend to be high in order to maximize hole cleaning, potentially leading to body erosion and reduced bit life. However, tungsten carbide matrix is less strong than steel and this means that matrix bodied bits generally have wider blades and reduced standoff, limiting the open face volume that can be achieved.

The paper focuses on drill bit development for a specific natural shale gas play located within North America. These wells require advanced horizontal drilling techniques and extensive hydraulic fracturing to make them economically attractive. This paper details how a major operator has been able to make radical improvements in drilling performance in this area, leading to significant cost reductions. A typical well consists of a vertical section, build section, and a final horizontal leg. When the operator started this project in 2008, the objective was to drill this entire main hole in just three bit runs; one for each directional leg described prior. In actuality, twelve to fourteen bits were utilized, averaging over forty days from drill-out to section TD. This made the economic viability of further development questionable. A team approach enabled bit design modifications and improvements to be implemented in a controlled, continuous, and closely monitored program. A key component of this was the development of a unique flexible bit design developed specifically for directional applications in coordination with a leading supplier of motors. These bits contain novel features that allow rapid design modifications to be performed locally, significantly reducing response time, and allowing the program to proceed at a much faster pace than previously possible. Within a matter of months, this systematic cooperative approach enabled the operator to achieve the initial objective of drilling the interval in 3 bit runs, but also their subsequent objective of drilling the interval in just two bit runs. Days to drill this section were drastically reduced from over forty to less than twelve days. The savings produced by this huge improvement in drilling performance has greatly assisted the economic viability of continued development in this basin.