As wellbores and drilling operations have become more complex, drill bit development must keep pace to meet increasingly difficult performance requirements.

Polycrystalline diamond compact (PDC)   drill bits have  seen  consistent improvements in durability and efficiency to support   enhanced operating parameters as well as BHA designs that include powerful motors and  sophisticated   rotary   steerable systems. These performance gains are largely the result of improvements in the toughness   and durability of the PDC cutters themselves, but design features and relentless iterative product   development have also played a part.  

While  R&D  resources are being applied to PDC bit development, the  key  performance indicators for   drill bit applications are becoming somewhat restrained.  It’s  difficult to reduce the number of   bits per section when most   hole  sections are already drilled with   one bit . It is  equally challenging to   significantly  increase ROP  when  hydraulic configurations cannot efficiently  evacuate drill  cuttings  up the annulus . Additionally, wellbore quality and   directional requirements sometimes override the desire to drill faster.  

As a result, one innovation that can drive further performance gains is broadly categorized under the   label of “smart bits.” At National Oilwell Varco, the ReedHycalog business unit has moved to the   forefront of the smart bit market, developing  technologies  that measure various aspects of the drilling   environment, communicate those measurements, and modify themselves downhole based on that   information.  

High-frequency measurement of downhole parameters and vibrations became part of the ReedHycalog   portfolio in the late 1990s. Since then,  the company  has continued to develop and deploy new   measurement technologies for internal research, product development, and drilling optimization   projects. Near-bit and at-bit measurements are a significant advancement that provided NOV product   engineers with crucial information as they worked to improve the drilling efficiency of PDC bits .  Engineers also discovered that near-bit and/or at-bit measurements could be combined with   measurements farther from the bit to improve BHA models, overall directional control, and the stability   of the drilling system.  

Drilling parameter and vibration measurement tools are now incredibly accurate and gather data at an   impressive frequency. Once processed, the data can provide significant insights into downhole dynamics   and efficiency as well as less obvious topics such as wellbore quality and formation characteristics. By   taking these measurements at the bit rather than several feet above within the BHA, it provides an   immediate look at many aspects of the drilling process as well as information on the formations bring   drilled.  

One intriguing application for these downhole measurements is the potential to use the data in neural   network   or big-data analyses. If we can capture downhole data across the entire depth of many wells   within a field, we can draw new conclusions about drill bit selection and BHA design, parameter   optimization, and geological trends. Many of these statistical analyses can be automated—the limiting   factor is the availability of  a high volume of  quality data .  

The  relative high costs related to many types of measurement tools have limited their   deployment, and, as a result, typically less than 10% of wells in a given application will include tools that   capture high-frequency data. ReedHycalog is working to improve these statistics.  

To improve the accessibility of near-bit, downhole data acquisition,  the service provider  is currently deploying a   small, low-cost data recorder that records and stores data on all ReedHycalog PDC bits in specific   applications. The @bit recording device is a 1.6-in.   diameter plug that fits securely in the shank   of any bit using a 4½-in. API pin or larger ,  Fig. 1 .  The recorder has a 15,000-psi maximum pressure and a 257°F   maximum operating temperature. Even with its tiny size, the @bit device is capable of 100 Hz   sampling rate and 200 hr of operation in the downhole environment while recording three-axis   vibration, downhole temperature, and RPM.  

Throughout the development of this tool, the emphasis has been on ease of use. The @bit device does   not affect the BHA design, and the carrier takes minutes to install or complete its data download. By   making the @bit device affordable, both in terms of hardware and manpower for implementation, it can   be broadly deployed across a target field.  

Due to its extremely small size, the device cannot store  large  amounts of data .  However, it   automatically processes data while downhole and stores that information for when it is needed to   support decisions about the dynamic performance of the bit.  

The @bit data are collected post run in an almost completely automated system, further reducing the   expense of analysis. A simple, one-page report is automatically generated, providing vibration statistics   for the run that are broken down by day. The data are indexed and uploaded to a database  where  drilling experts can work with  operators  to analyze performance trends via a map   interface.  

Applying smart adaptation to reduce bit trips .   As previously mentioned, many hole size sections around the world are now drilled with a single bit,   which is a result of advances in drill bit durability as well as improvements in other drilling systems such   as motors, rotary steerable tools, and MWD components. Considering the costs of tripping in and out of   hole, which are particularly high in offshore applications, this is a significant development from the   viewpoint of operator costs.  

The downside to this reduction in bit changes during the drilling process is that once the drill bit has   been selected and run downhole, that same bit will often be used to drill many different formation   types under different pressure and hydraulic regimes. The same bit can potentially be tasked with varied   directional objectives, as well—all while drilling at a high ROP.  

In most cases, the driller typically has limited control over the drilling performance optimization that has   been committed to the well plan, with input mainly based on operating parameters. This emphasizes   the importance of good parameter planning, bit selection, and BHA design. However, compromises must   be made in most plans due to the changing downhole conditions throughout the run.  

To  address  this challenge,  ReedHycalog  has developed a new technology that allows the bit to adapt and   change while downhole, thereby eliminating a trip to surface. The new technology offers the potential   for bits to adapt to changing dynamic environments, formation characteristics, directional requirements,   and more. In this way, the bit can drill at the highest possible efficiency for the entirety of its downhole   lifecycle—improving ROP, wellbore quality, and directional profile while reducing the likelihood of   catastrophic   failure for the bit or BHA components.  

Current testing of these “smart-adapting” bit concepts is allowing the driller to deploy additional cutting   structure or depth-of-cut limitation elements during the drilling process. In the first prototype of this   technology, the adaptation is triggered via changes in hydraulic parameters, but future versions will   utilize other deployment methods. The technology can be deployed in several valuable ways.  

In one such example, a driller selects a bit that drills very aggressively through the first half of an   application, where the formations are relatively soft. To accomplish this, a relatively light-set bit with six   blades would be used. As the drilling operation encounters extremely abrasive sands, the six-blade bit   that worked so well in the top of the hole will not survive this section as noted in offset wells, requiring a   costly trip for a new, application-specific bit. With ReedHycalog’s smart-adapting bit technology, a   driller can deploy additional blades with fresh cutters, providing enhanced durability  so the BHA can finish the  section without pulling  out-of-hole to replace the dull bit ,  Fig. 2 .  

The smart-adapting drill bit can also benefit directional applications, in which the curve and horizontal   sections are drilled with a single hole size. For the curve, depth-of-cut control is required on the bit in   combination with a bent-housing motor to ensure a smooth torque response. To accomplish this, the   smart-adapting bit deploys depth-of-cut control elements that reduce torsional fluctuations and tool   face control issues. However, after completing the curve, offsets show the lateral can be drilled at an   ROP three or four times faster than what is achieved in the curve. In this case, the smart-adapting bit   can retract the depth-of-cut control elements to allow greater penetration of the cutting structure,   allowing the bit to drill the horizontal as quickly as possible ,  Fig.  3 .  

In addition to these operational benefits, other scenarios include the ability to significantly change the   cutting structure, ga u ge configuration,  and/ or hydraulic design while downhole to further optimize   performance.  

N ew synergies  going forward .   As technology and material  science  advance, new at-bit measurement  products  will   be developed by the   industry, leading to information provided in real time for drilling optimization ,  as well as in memory   for post-well analysis. Drill bit suppliers and operating companies must work together to identify what   information from the bottom of the well provides the greatest value and how quickly those data are   needed to maximize value.  

Smart-adaptive bit control can be exerted from the surface via various downlink methods that are   already in use around the industry. Ultimately, these methods may be too time consuming and not   provide the reactive control needed.  

Smart-adaptive bit development should be working towards systems that require no direct interaction   with surface personnel. As these smart bits acquire measurements, those data should be combined with   measurements from other tools in the BHA, as needed. When the required information is in place, the   bit (and other portions of the BHA) should then react and adapt to the changing conditions without   interference from the surface. These closed-loop capabilities have the potential to dramatically improve   drilling efficiency and improve processes such as geo - steering and at-balance drilling as smart bit   designs progress in  the coming years .  

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