Bit designs take a leap

With more than 64% of the world drilling records for bi-center bits last year, DPI has become a recognized leader in bi-center drill bit technology.

DIAMOND PRODUCTS INTERNATIONAL (DPI)

With more than 64% of the world drilling records for bi-center bits last year, DPI has become a recognized leader in bi-center drill bit technology. Several recent field run applications have resulted in a unique design modification that is opening up new and exciting applications for the SpeedReamer bi-center bit.

SpeedReamer SRF+ and CSD+ Bi-Center Drill Bits

Since 1994, DPI has continued to improve the performance and expand the applications of the SpeedReamer bi-center bit series. In May of 1999, DPI invented the SpeedReamerCSD, a bi-center bit with casing-shoe drilling capability. On this initial application, the bit was able to drill out the casing and liners and then continue to drill ahead successfully. It produced improved drilling performance in vertical, build and tangent sections and saved five trips on a single well, resulting in a cost savings of US $889,000.

A new design, the SpeedReamerSRF+, adds a new dimension to the highly successful SpeedReamer bi-center bit series. The SpeedReamerCSD+ incorporates all the standard CSD design features, adding a "Mid-Reamer" section. This feature not only allows the CSD to ream out a pilot hole, but also provides geometric stability for improved performance.

SpeedReamerSRF+ Drilling an Existing Core Hole

When a core is required in the middle of a bi-center run, the pilot bit of a standard bi-center is usually smaller than the core hole. This causes the standard bi-center to drill an undersized hole when reaming through the core hole. The mid-reamer on the SRF+ can be designed to match the size of the core hole. With the core hole size and the mid-reamer size matched, the bi-center will produce the correct hole size when reaming the core hole.

A recent run for a major operator in deepwater Gulf of Mexico illustrates the advantages of this new design. A 105/8-in. x 115/8-in. SRF+444M2 was selected to drill several hundred feet of 81/2-in. core hole, open the hole to 115/8 in., then drill ahead in new formation. The bit drilled out the rat hole with excellent stabilization and saved the operator an additional trip.

SpeedReamerCSD+ Drilling an Existing Pilot Hole

In a more recent application, the new CSD+ bit was used to open an existing pilot hole that was drilled for wireline well logging purposes. After logging was complete, the operator had a 121/4-in. hole in which he wanted opened to 191/2-in. The 161/2-in. x

191/2-in. CSD+044 allowed for the pilot hole to be drilled and opened with the 131/2-in. mid-reamer then reamed out to a full 191/2-in. for the 3,000-ft (900-m) section. It then drilled ahead in new formation for another 1,000 ft (305 m) and 16-in. casing was set.

HALLIBURTON SECURITY DBS

Advances in PDC Cutter Development

Polycrystalline Diamond Compact (PDC) has been a key technology Security DBS has invested in heavily throughout the years for its fixed cutter product line. The company continues to advance PDC technology as drilling needs change due to demands in the industry and as PDC bit applications expand. The RING CLAW was one of the first PDC cutters that incorporated an aggressive non planar interface designed to mitigate residual stresses, was balanced between impact and abrasion resistance and offered a cutter that differentiated itself in the field. In 1999, Security DBS developed the DEEP RING CLAW, a PDC cutter with three times the diamond volume, and the first PDC cutter with a diamond thickness over 0.150-in. The DEEP RING CLAW extended the life of the cutter in applications where life was critical. Both the RING CLAW and the DEEP RING CLAW cutters have become standards in the industry.

In the past year, Security DBS has made strides in addressing cutting efficiency, a new variable to the balance between impact and abrasion resistance. Cutting efficiency is the ability to shear rock during the drilling operation with the least amount of energy. The new CLAW RING CLAW (CRC), now available for inclusion in Security DBS' FM3000, FM2000, SE3000 and FS2000 Series line of fixed cutter bits, incorporates interface features that mitigate harmful residual stress components, diamond table technology that increases abrasion resistance without a loss of impact resistance and a choice of four different edge preparations depending on the application. Every feature of the CRC cutter is designed to increase the efficiency of Security DBS' fixed cutter bits, thereby lowering overall drilling cost.
This latest cutter technology from Security DBS is delivering significant increases in cutting efficiency, with an increase in the abrasion resistance being five times greater than what was offered just over a year ago. The company is continuing to focus and lead the way in PDC bit and cutter development for the drilling industry.

HUGHES CHRISTENSEN (HCC)

New hard and abrasive Genesis XT PDC introduced

Hughes Christensen recently introduced Genesis XT, an extension of Genesis product line that expands the application envelope of PDC drilling into harder and more abrasive formations. Building on the Genesis multi-functional team approach, HCC engineers have incorporated a new generation of cutters and patented depth-of-cut control technology to increase bit stability and durability in demanding applications.

Odyssey Series Cutters - Engineers optimized the interface between the tungsten carbide substrate and the synthetic diamond table to improve cutter toughness. In addition, the latest innovations in layered diamond table technology have been applied to provide superior abrasion resistance.

SmoothCut - Award-winning EZSteer depth-of-cut control technology has been adapted for general-purpose applications to provide smoother, more stable drilling, especially through interbedded formations. This improves bit longevity and overall drilling efficiency.

Genesis XT technology provides longer, faster runs through formations previously drillable only with roller cone bits.

Slimhole Mini-MX

Hughes Christensen has also introduced a new slimhole line of metal sealed TCI and steel tooth Tricone bits, optimized for drilling long directional or horizontal wells. The new "Mini-MX" bits are the latest addition to the UltraMax line of motor bits that are specifically designed for demanding, high speed applications. Mini-MX is a premium small diameter bit with all the features of a larger UltraMax bit. Technologies to protect the bearing seal have been integrated into a smaller metal sealed bearing package with tighter tolerances and greater reliability than an elastomer sealed bit.

Metal Seal Bearing

Mini-MX utilizes HCC's patented single energizer metal seal (SEM) system to provide a more robust alternative to elastomer sealed bearings for high-speed directional drilling, which often require high total bit revolutions to achieve directional objectives and finish the hole section. The SEM system relies on a metal face seal where all relative rotary motion occurs between two highly polished and lubricated metal surfaces. This type of low friction metal face seal thrives at higher rotary speeds (200 to 300+ rpm), whereas radial elastomer seal performance tends to degrade at these rotary speeds resulting in accelerated elastomer seal wear and reduced bearing life expectancy.

Mud packing is a common occurrence in bits used on motors and in directional applications, particularly when drilling shales and claystones. To address this issue, Mini-MX uses "Excluder" technology targeted specifically at preventing the detrimental effects of mud packing. A mud wiper TCI button works in tandem with a groove in the cone backface to wipe away cuttings, which tend to adhere to the cone. Finally, to keep the metal seal bearing well lubricated, the Mini-MX utilizes the "Equalizer" lubrication system, which is an advanced pressure compensation system that features a spring loaded cap to reduce vibration & fretting and a pinhole relief system to limit internal pressure build up.

Optimized Hydraulics

A patented "Clean Sweep" nozzle configuration cleans areas of the cutting structure prone to bit balling and provides return flow through deep junk slots for better cuttings evacuation. This advanced hydraulics system ensures high penetration rates throughout the run. Mini-MX bits are available in the 57/8-in. to
63/4-in. size range over a wide range of IADC classifications.

PRECISION DRILLING

PDC bits from Precision Drilling aid rotary steerable drilling

With more than 50 bit styles and sizes, Precision Drilling's United Diamond (UD) division is a leader in Polycrystalline Diamond Compact (PDC) bit design. UD's shankless, single-piece bits have a flat profile that optimizes depth-of-cut from bit center to gauge. Using the latest cutter technology, new premium, nonplanar cutters provide greater impact resistance and abrasive resistance than other PDC bits, resulting in increased drilling efficiency. The bit's unique design, cutter placement, profile and nonplanar cutters produce consistent torque and smooth, predictable build rates.

UD PDC bits are created with proprietary 3-D modeling software that provides quality assurance and repeatability of design. Force balancing is part of every bit design to provide a high stabilization factor. These designed stabilizing forces allow UD bits to drill harder lithologies with improved penetration rates (because of less bit damage from downhole vibration) and create a constant reactive torque value, and therefore a constant toolface for steering.

The TruGauge tool is a spiral-bladed, steel-bodied bit sub with fused carbide hard facing. Spiral blades on the tool match up to blades on UD PDC bits, extending gauge protection and eliminating the need to ream long sections of undergauge hole. This tool has helped eliminate hole-ledging caused by rotating with a bent housing in directional wells. The TruGauge tool combined with the UD PDC bit allows lower bent housing settings to be used and still achieve nominal build rates. Lower bent housing settings mean less chance of hole-ledging, and therefore less hole tortuosity.

UD's one-piece, steel-bodied PDC bit has worked well in rotary steerable applications, which have been proven in several tests with Precision's rotary steerable system at the Advantage Engineering research facility in Houston, Texas, and in the field. This combination, along with TruGauge technology, maximizes rotary steerable performance, producing a clean, smooth well bore and consistent build rates while reducing tortuosity caused by high doglegs or hole ledging. A smooth well bore allows greater weight transfer to the bit, resulting in higher penetration rates and longer bit life.

A typical bottomhole assembly with a rotary steerable configuration includes a UD PDC bit, TruGauge tool, near-bit stabilizer, rotary steerable system, measurement while drilling (MWD) tool and drillstring stabilizer. UD PDC bits have been used successfully on more than a dozen Precision rotary steerable runs, as well as several other industry rotary steerable systems.

REED HYCALOG

Bit Durability is the Key to Advanced Drilling Methods

Durability is the key to significant improvements in drilling efficiency in today's drilling environment. To drill a well in less time, operators need to improve the overall drilling rate and reduce non-productive trip time. The use of fixed cutter bits to shear formation offers the greatest improvement in penetration rate. Combining this cutter technology with stable bit designs allows operators to drill further, faster. More durable fixed cutter designs, therefore, improve drilling efficiency.

Roller cone applications also benefit from improved durability. Modern well designs and drilling equipment deliver more energy to the drill bit in more demanding loading conditions than ever before. New tougher bit designs, with more robust cutting structures are necessary. Once again durability is the key to improved drilling performance.

Roller Cone bit Technical Advances

The TuffDuty Directional series of roller cone bits combines a tougher bearing system with a cutting structure designed to address the rigors of drilling on a steerable assembly. Key design aspects include a tougher bearing system, kerf wear resistant main and inner row insert features, improved cone and insert retention technologies, advanced hydraulics, enhanced gauge durability and new high-performance hard facing on tooth bits.

When a steerable assembly is rotated, the bit can be subjected to off- center rotation, which can lead to tracking and kerf wear, as well as high side loading. These conditions can reduce bearing life and damage the gauge and shirttail areas of the bit.

TuffDuty Directional bits specifically address off- center wear with features such as KerfStop inserts, progressive skip spacing, enlarged nose insert and strategically staggered insert rows called WideCut. The combination of KerfStop, WideCut, and the oversize nose insert, significantly reduce cutting structure damage resulting from kerf build-up.

TuffDuty Directional Bits deliver durability and performance in the most demanding drilling applications.

Fixed Cutter Bit Technical Advances

TReX cutters feature a self-sharpening, ultra wear-resistant, thermostable layer on the cutting face of a premium PDC cutter. Tests demonstrate that this integral layer is 400% more abrasion resistant and 200% more temperature resistant than the highest-grade PDC materials. ReedHycalog designed, developed and patented TReX technology. TReX cutters can only be produced in ReedHycalog's manufacturing, research and development facility and are exclusive to ReedHycalog.

ReedHycalog's SteeringWheel bit designs significantly reduce bit whirl and therefore lateral vibration. Reduced vibration results in reduced impact damage. The combination of the ultra-wear resistant TReX cutters with the reduced impact damage of SteeringWheel bits has allowed operators to significantly improve drilling performance in hard, abrasive formations. In East Texas, SteeringWheel bits fitted with TReX cutters have drilled the very abrasive Travis Peak and Cotton Valley formations on over 300 runs in the past 2 years. No other bit has completed this well interval. Compared to average offsets these bits have typically replaced three or four hard formation (637-837) insert bits and eliminated multiple trips.

Conclusion

Meeting demands for increased durability requires bit designs that incorporate a full range of technologies, from bit dynamic mathematical modeling to materials, components and bit body configuration. Singularly and in combination, these design changes are resulting in faster, more efficient drilling campaigns.

ROCKBIT INTERNATIONAL (RBI)

RBI-Gearhart has developed a new line of products for hard rock applications, including new gage protection known as Wrap Gage.

Where the LRG offered 200% improvement in gage protection, the Wrap Gage feature offers nearly 300% more inserts to maintain gage; this combined with the new cone geometry and strategically placed diamond enhanced inserts allows the Wrap Gage to drill faster and hold gage in hard rock drilling applications.

A consistent set of inherent problems exists in the ever-growing market of bi-center, RWD, SRWD family of products. RBI-Gearhart has developed the RCER for such problematic situations.

The RC line of Eccentric Reamer Technology addresses the problems of torque, noise, stability and vibration while giving the operator the choice of using "bi-center" bits in harder formations. The rolling cutter helps to alleviate the constant problem of torque while causing a much lower noise/vibration situation downhole. While PDC style cutters can drill most soft to medium formations, the new RCER can address all formations from soft to very hard formations giving this line greater overall possible drilling applications. The new tool, combined with RBI-Gearhart's "RSA" software will allow the RBI engineering team to drill holes previously thought to be completed utilizing only under reamers. The RCER design allows both flexibility in rolling cutter selection and the pilot bit as well, allowing for maximum options in proper bit selection.

RBI-Gearhart's also developed a new one-cone product line has been developed for slim-hole applications. In a standard one cone, the bearing and seal is over 300% larger than a comparable three-cone bit. This eliminates the concern of bearing failure in slimhole drill bits. The current Eliminator is used in soft to medium formations. However, the newest line will attack the medium to hard classification of formations. This bit, with the proper bottomhole assembly has replaced three to five similar three-cone bits with the same or higher rates of penetration.

SMITH INTERNATIONAL

SmithBits division offers a new line of bits featuring lots of options and design innovations. The Xplorer Expanded line of milled tooth bits is offered in two configurations. The XR+ has a conventional straight tooth cutting structure, while the XR+i features a twisted tooth cutting structure. These bits include Flex-Flo hydraulics, IDEAS designs, MIC2 hardfacing and the latest generation of Gemini seals.

The XR+ and XR+i cutting structure options give the customer the ability to choose the product most closely matched to the formation being drilled. The XR+i teeth are specifically twisted to optimize rate of penetration (ROP) in given formations.

This choice is further enhanced by having the opportunity to select the Flex-Flo hydraulics mode that is most appropriate for the drilling conditions being encountered. S-Flo uses three identical nozzles to allocate hydraulic energy to prolong bit life. V-Flo uses three precisely directed nozzles to allocate hydraulic energy for improved penetration rates through superior cutting structure cleaning, and efficient cuttings evacuation.

Extensive research in materials technology has produced the new MIC2 hardfacing material. This ultra wear-resistant substance provides outstanding durability. According to the company, the full cap application of MIC2 yields a 35% to 60% increase in hardfacing per tooth compared to previous designs.

VAREL INTERNATIONAL INC.

New tungsten carbide technology from Varel improves bit performance

Varel International has developed new sintered tungsten carbide insert technology that is significantly improving rock bit performance. The technology is based on a new manufacturing process called High Energy Tumbling (HET) that replaces the traditional step of tumble-polishing sintered tungsten carbide parts.

The traditional method for making sintered tungsten carbide parts is to press blended grade powder into the desired shape using dies and a mechanical or hydraulic press. The pressed parts are then sintered under gas pressure. After sintering, tungsten carbide inserts have the cylindrical diameter precision ground. After grinding, the parts are tumble-polished to break any sharp edges on the parts and improve the overall surface finish. The improved surface finish improves the durability of the inserts slightly by minimizing stress risers on the part surface. Tungsten carbide inserts produced by this traditional process are reasonably homogeneous throughout.

The new process developed by Varel International differs from the traditional process by replacing the tumble polishing operation with a much more aggressive treatment. During the HET process, the parts are tumbled in a special machine that causes them to repeatedly collide with one another at high speeds. The impacts between the parts are intense enough that the insert surfaces undergo compressive deformation and are left with residual compressive stresses on all part surfaces. The surface hardness increases, and the surface finish of the parts improves beyond what can be achieved by traditional tumble polishing. The overall effect on the insert is that it is much more resistant to breakage under the high loads that bit teeth are subjected to.

Impact tests performed on standard and HET processed inserts showed the HET process significantly improves insert durability. Impact levels that caused catastrophic breakage of standard inserts 91% of the time were found to only damage identical HET inserts 14% of the time. In static bending tests where inserts were loaded to failure, HET inserts were able to survive 210% higher loads than traditionally processed inserts.

Field tests of roller cone bits with HET inserts showed dramatic improvements in durability when compared with standard bits. Several 77/8 CH39 (IADC 547Y) rock bits with and without HET inserts were run for comparison in Ector County, Texas. The bits with HET inserts averaged 17% higher penetration rates and saved an average of US $6,278 per bit run as compared with 77/8 CH39's with traditional inserts. The higher overall penetration rates were due to reduced breakage of the HET inserts while drilling hard, dense stringers that normally damage conventional bits.

Similar results were shown by 77/8 CH09 rock bits (IADC 427) run in Denton County, Texas. The bits with HET inserts drilled an average of 326 more feet (99 m), at an 8% higher average penetration rate as compared with the same bits with standard tungsten carbide inserts. As with the CH39's, the higher average penetration rates were due to the bits staying sharper throughout the runs. Average savings per bit to the operator was $1,512.

Varel International has applied for patent protection for the HET process. Varel's popular Challenger line of premium motor bits is presently being converted to feature HET inserts in all cutting rows.