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

The durability and efficiency of polycrystalline diamond composite (PDC) drill bits continue to improve to support enhanced operating parameters and BHA designs, including powerful motors and complex rotary steering systems. These performance improvements are largely the result of the improved toughness and durability of the PDC tool itself, but the design features and continuous iterative product development also play a role.  

While R&D resources are being used for PDC bit development, the key performance indicators for bit applications have become somewhat limited. When most of the hole sections have been drilled with one drill bit, it is difficult to reduce the number of drill bits for each section. It is also challenging to significantly increase the ROP when the hydraulic configuration cannot effectively push the drill cuttings upwards out of the annulus. In addition, borehole quality and direction requirements can sometimes overwhelm the desire to drill faster.  

Therefore, an innovation that can further improve performance is broadly classified as a "smart bit" label. At National Oilwell Varco, the ReedHycalog business unit has been at the forefront of the smart drill bit market, developing technologies to measure all aspects of the drilling environment, communicating these measurement results, and making self-modifications downhole based on this information.  

In the late 1990s, high frequency measurements of downhole parameters and vibration became part of ReedHycalog's product portfolio. 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 bit measurement is a major advancement, providing important information for NOV product engineers to improve the drilling efficiency of PDC bits. Engineers also discovered that near-bit and/or drill-bit measurements can be combined with measurements far away from the bit to improve the BHA model, overall directional control, and stability of the drilling system.  

Drilling parameters and vibration measurement tools are now very accurate and collect data at an impressive frequency. After processing, the data can provide important insights into downhole dynamics and efficiency as well as less obvious topics such as borehole quality and formation characteristics. By taking these measurements a few feet above the bit instead of the BHA, it can immediately see many aspects of the drilling process and information about the drilling formation.  

An interesting application of these downhole measurements is the potential of using data in neural networks or big data analysis. If we can capture downhole data for the entire depth of many wells in an oil field, we can draw new conclusions about 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 large amounts of high-quality data.  

The relatively high costs associated with many types of measurement tools limit their deployment, so in a given application, typically less than 10% of wells will include tools to capture high-frequency data. ReedHycalog is working hard to improve these statistics.  

In order to improve the accessibility of near-bit and downhole data collection, service providers are currently deploying a small, low-cost data logger to record and store all ReedHycalog PDC bit data in a specific application. @bit recording device is 1.6 inches. Diameter plugs, use 4½-in. API pins or larger, Figure 1. The maximum pressure of the recorder is 15,000 psi and the maximum operating temperature is 257°F. Even if the size is small, the @bit device can operate in a downhole environment with a sampling rate of 100 Hz and 200 hours while recording triaxial vibration, downhole temperature and RPM.  

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

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

@bit data is collected after operation in an almost fully automated system, further reducing analysis costs. A simple one-page report is automatically generated, providing operating vibration statistics broken down by day. The data is indexed and uploaded to the database. Drilling experts can work with operators to analyze performance trends through the map interface.  

Apply smart adaptation to reduce bit travel. As mentioned earlier, many parts of wellbore sizes around the world are now drilled with a single bit due to improvements in drill bit durability and improvements in other drilling systems such as motors, rotary steering tools, and MWD components. Considering the particularly high cost of entering and exiting the wellbore in offshore applications, this is a major development from the perspective of operator costs.  

The disadvantage of reducing bit changes during drilling is that once a bit is selected and drilled downhole, the same bit is usually used to drill many different types of formations under different pressure and hydraulic conditions. The same bit may also have different directional targets-while drilling with high ROP.  

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

To meet this challenge, ReedHycalog has developed a new technology that allows the drill bit to be adjusted and changed while it is downhole, thereby eliminating the trip to the surface. The new technology provides the drill bit with the potential to adapt to the ever-changing dynamic environment, stratum characteristics, direction requirements, etc. In this way, the drill bit can drill as efficiently as possible during its entire downhole life cycle—improving ROP, borehole quality, and directional profile, while reducing the possibility of catastrophic failure of the drill bit or BHA component.  

Current testing of these "smart adaptation" bit concepts allows drillers to deploy additional cutting structures or cutting depth limiting elements during the drilling process. In the first prototype of the technology, adaptability was triggered by changes in hydraulic parameters, but future versions will use other deployment methods. The technology can be deployed in many valuable ways.  

In one such example, the driller chose a drill bit that was drilling very aggressively in the first half of the application, where the formation was relatively soft. To achieve this, a relatively light drill bit with six blades will be used. Since drilling operations will encounter extremely abrasive sand particles, a six-edged drill bit that works well at the top of the hole will not survive this section as described in the adjacent well. It requires expensive down-drilling for new, application-specific drill bits. . With ReedHycalog's smart adaptable bit technology, the driller can deploy additional blades with new tools, providing greater durability, so BHA can complete this part without having to pull out the hole to replace the blunt bit, Figure 2.  

Intelligently adaptable drill bits can also benefit directional applications, in which curved and horizontal sections are drilled with a single hole size. For curves, it is necessary to combine the curved shell motor on the drill to control the depth of cut to ensure a smooth torque response. In order to achieve this, the intelligent adaptive drill bit deploys a cutting depth control element to reduce torsional fluctuations and tool face control problems. However, after completing the curve, the offset shows that the lateral well can be drilled with a ROP three to four times faster than the speed achieved in the curve. In this case, the smart adaptable drill bit can retract the cutting depth control element to allow a larger cutting structure to penetrate, so that the drill bit can drill on a horizontal surface as quickly as possible, Figure 3.  

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

There will be new synergies in the future. With the advancement of technology and material science, the industry will develop new bit measurement products to provide real-time information for drilling optimization and perform post-well analysis in memory. Bit suppliers and operating companies must work together to determine which information from the bottom of the well provides the most value, and how quickly the data is needed to maximize value.  

Intelligent adaptive bit control can be performed superficially through various downlink methods that are already in use in the industry. Ultimately, these methods may be too time-consuming and fail to provide the required response control.  

The development of intelligent adaptive drill bits should focus on systems that do not require direct interaction with ground personnel. When these smart bits acquire measured values, they should be combined with the measured values ​​of other tools in the BHA as needed. When the required information is in place, the drill bit (and other parts of the BHA) should react and adapt to changing conditions without being disturbed by the surface. As smart bit design advances in the next few years, these closed-loop functions have the potential to significantly increase drilling efficiency and improve processes such as geosteering and balanced drilling.  

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