New materials, a better understanding of rock mechanics and hydraulics, extreme drilling environments, improvements in BHAs, high activity levels and unique applications have all driven ongoing drilling bit innovation. Across the board, involved companies are leveraging internal resources to meet the new performance requirements. Some of the latest achievements not already covered are noted.
Security DBS (Halliburton)
• This manufacturer has introduced the concept of energy balanced bits that recognize the amount of formation removed by each cutter on a bit is different. Forces acting on each cutter differ so they need to be balanced to avoid overloading individual cutters and blades. The company’s Energy Balanced® Series bits are force and volume balanced to create even wear for extended bit life and optimized performance.
• Patented Claw Tooth and Diamond Tech2000 hardfacing technology now incorporates diamond inlays in steel tooth cutting structures, to help extend performance in premium steel tooth products.
Hughes Christensen (Baker Hughes)
• To enhance steerability, Hughes Christensen has introduced EZSteer® depth-of-cut control technology in many of its bits. Bearing surfaces near the center of the bit are designed to engage the bottom hole in slide mode, but not in rotate mode. This tempers the aggressiveness when steering and preserves ROP while rotating. In a related development, new Zenith® Series cutters have been used to optimize internal cutter geometries and control residual stress, improving cutter toughness and abrasion resistance.
• Also new is the EZCase® casing bit system (EZC) to aid in getting casing to existing total depth (TD), drilling through trouble zones, controlling hole instability and lost circulation zones. The system can be used in one continuous operation or after the hole has been drilled conventionally. EZC’s full polycrystalline diamond cutting (PDC) structure allows it to drill and/or ream farther in harder, more abrasive formations than was previously possible.
• For hole enlargement, the new RWD2 (rotary), RWD2S (steerable) and RWD2ST (slimhole) fixed blade eccentric reamers have been designed to tackle hole opening applications in the most demanding well bore geometries without the risks and performance limitations associated with bi-center bits and conventional underreamers.
• MXL bearing technology, third generation metal face seals with improved bearings, now allow higher loads and higher RPM on roller cone bits.
Smith Bits (Smith International)
• SHARC (Smith High Abrasion Resistance Configuration) bits have been recently introduced for tough formations that may be highly abrasive and inter-bedded. Cutting structure layouts feature two rows of cutters set on each blade for reinforcement and to provide maximum durability over the critical nose and shoulder areas of the bit.
• The SHARC bits were designed using Smith’s new IDEAS bit design software. The sophisticated computer-based engineering design tool combines laboratory-derived data about cutter and rock interaction with innovative new methods of designing and optimizing the bit’s cutting structure such as 4-D simulation.
• FH tungsten carbide insert (TCI) bits are now run to increase drilling efficiency and drive down drilling costs. The FH platform emphasizes Fast Hole Cutting Structures, Formation Hardy, Materials, Field Honed Reliability and Flexible Hydraulics Options.
• Newly marketed Kinetic bits use a combination of application specific features and materials to withstand the most rigorous drilling conditions. The bits are built using Grit Hot Pressed Inserts (GHI), PDC cutters.
Varel
• Varel has developed the MBCSeries bicenter bits that use Casing-SaverTM cutter technology and a one-piece construction matrix to deliver optimum performance inside the casing during drill-out. The company has also introduced Challenger premium roller cone bits with aggressive cutting structures and High Energy Tumbling (HET) technology to reduce insert breakage. In another development, Varel’s VBSeries fixed cutter bits now use oval cutters and lateral jets in applications where performance is premium. Additionally, the company’s Navigator bits have been designed with proprietary software for enhanced steering and wellbore quality in directional applications.
ReedHycalog (GrantPrideco)
• TuffCutter® roller cone drill bits from ReedHycalog now extend the traditional boundaries of tooth bits into the range of soft formation insert bits. Manufactured utilizing a patented and proprietary powder forging process, the bits feature consistent, wear-resistant tungsten carbide for a durable, aggressive cutting structure that remains sharper, longer.
• New second generation Raptor® cutters have broadened TreX thermostable features over the entire circumference of the cutter as well as the face for increased PDC bit life and ROP. ReedHycalog believes the “game-changing” technology means many previously non-PDC drillable formations are now targets.
• The company has also developed a SystemMatched® RS rotary steerable line of fixed cutter drill bits. They feature unique and patented cutting structures specifically designed to optimize performance of the entire directional assembly. A SmoothSteer® Gauge is used to enhance performance via reduced torque fluctuations and vibration minimization.
Drilling Fluids Play a Greater Role
Increased efficiency in nearly all aspects of drilling has aided the continued evolution of drill bit technology. Performance improvements have been seen in many areas including lower mechanical failure rates, significantly reduced drilling times through increased hydraulic horsepower, draw works innovations and even cost savings during rig moves. Individually and collectively many technical enhancements have positively impacted the drilling environment, including drilling fluids.
One of the major factors affecting how fast a bit drills and how long it lasts, are the drilling fluids which transport cuttings to the surface, cool and clean the bit and even help collect MWD/LWD data. Although drilling fluid averages only 10% of the total tangible costs of well construction, drilling fluid performance can help reduce costs throughout the drilling operation by enhancing the penetration rate, protecting the reservoir, stabilizing the wellbore and helping the operator remain in compliance with environmental and safety regulations. Drilling fluids are today rapidly becoming an even greater factor in the overall success of drilling operations and bit performance.
For instance, deep drilling depends heavily upon drilling fluids to act as a lubricant and reduce torque and drag on the drill pipe. As this market has expanded, the role of drilling fluids has become increasingly important.
Extreme conditions can result in the failure of the drilling fluid to perform as needed, so careful planning is necessary to match the fluids to the operating conditions and of course, the bit.
There are three types of drilling fluids: water-based, oil-based and synthetic-based. The drilling fluid system, commonly called the “mud system”, is the only component of the well construction process that remains in contact with the wellbore throughout the entire drilling operation. A drilling fluid system is designed to perform efficiently under expected wellbore conditions.
Recent drilling fluid advancements have led to more stable wells that are drilled faster and cheaper with PDC bits using water based muds. PDC bits coupled with oil-based/synthetic-based muds have also set performance benchmarks for drilling shales especially in deep, high-pressured troublesome zones. PDC bit-balling problems have been best tackled using an integrated approach of optimizing both bit and drilling fluid. The use of ROP Enhancers has led to significant advancements improving formulations for reduced clay sticking.
There are now trends in fluids products similar to the displacement of roller cone bits by diamond bits. Unfortunately, the better lubricating qualities of oil-based and synthetic-based drilling fluids may become less available to drillers due to environmental regulations restricting their use. Because of this, drilling fluid companies are working closely with operators and bit manufacturers to develop new options. For environmental reasons, fluids are moving away from oil based products to new water based products like PERFORMAX® from Baker Hughes Drilling Fluids and PERFORMADRIL® from Baroid. These innovative products simulate many of the properties of an oil base fluid. Their growing use makes bit hydraulic design and flow efficiency more important. Drilling fluids are now one of the key performance enhancers in bit performance.
It’s Well Profitability that Counts in the End
Advances in drill bit technology have led to an impressive array of new roller cone and fixed cutter products that continue to reduce drilling costs. Innovations in materials technology have positively impacted tungsten carbide metallurgy and led to the further development of more impact and abrasion resistant PDCs. As part of this, there has been a market transition from roller cone to diamond bit types. In the development work today, every component of a bit is constantly being upgraded whether it be materials, bearings, grease, seals, cutting structure, or gage holding capability.
These improvements have been facilitated by the frequent application of highly sophisticated design and drilling application software and processes. To drill the more complex wells of today, operators are also scrutinizing all the dynamic influences affecting bit performance including BHA components, motor systems, fluids, and drive assemblies. Databases are being defined and captured to continually improve drilling performance.
In the end, economics remains the prime determinant of bit success. Savings and benefits are measured in many performance dimensions including ROP, durability, steerability and hole quality. When all of these factors are delivered together in a matched drilling system, drilling costs are reduced and the well’s profitability is maximized.
