B I T D E S I G N F O R R S S

NORTH SEA FIELDS continue to ben-efit from improvements in PDC bit androtary steerable technology. There are,however, issues relating to very hardimbedded formations that result in stick-slip, bit/BHA wear, shocks/vibration, toolfailures and short run lengths.

Rotary steerable systems (RSS) areessential to drill the tortuous well paths.Push-the-bit RSS tools, first employedwith early versions of point-the-bit sys-tems, resulted in premature tool failures.Tool modifications, increasing theirruggedness, led to longer runs, and newpoint-the-bit systems have reducedshocks/vibrations, allowing more toler-ance of the harsh drilling environment.

There has been an evolution in cuttertechnology/bit design. The cutters havehigher wear resistance and are able todrill formations that were previouslynot PDC-drillable. Bit designs evolvedas RSS tools have changed: point-thebit versus push-the-bit systems. Thenew point-the-bit systems require mod-ifications to bit gauge designs. Highstick slip and vibration are the mainconstraints to performance but aregreatly reduced by designing the bit tocomplement the RSS.

This paper will show how modificationsto bit designs based on the steering char-acteristics of RSS tools, and modifica-tions to operating parameters of the RSStools based on the characteristics of PDCbits, have been brought together to yielda significant improvement in drilling per-formance.

A New Approach to Stick Slip Manage-ment Integrating Bit Design andRotary Steerable System Characteris-tics (IADC/SPE 98962) MR Niznik, ADCarson, ExxonMobil; KJ Wise, Schlum-berger; F Carson, Reed Hycalog.

T W O - C O N E B I T S

Designers have always recognized greatadvantages in two-cone bits, which havenot fully lived up to their potential. Therehas always been concerns with vibration,directional responsiveness, holestraightness, mechanical reliability andhole cleaning, leading to their displace-ment by three-cone bits.

But technology advances have encouragedbit manufacturers to revisit older designs.

To date, six runs with a modern two-conebit design have taken place in the Texasand Louisiana Gulf coast. All runs arereported in this paper, detailing lessonslearned and successes from the new two-cone bit that have been shared by theoperators.

Unlocking Two Cone Bit Potential:Technology, People, and PlanningMake It Possible and the LessonsLearned (IADC/SPE 99017) PK Centala,Smith Bits; RJ Ford, Smith Tool; TLDunn, Ballard Exploration; T Burnett,MM Burley, Smith Bits; JP Sinesi, SmithInternational Inc.

L A T E R A L L Y S T A B L E P D C B I T S

Bit whirl is well-documented as a majorcause of damage to PDC drill bits, result-

ing in short runs, low ROP, high cost/ft,poor hole quality and downhole tool dam-age. Hence, consistent lateral stability ishighly desirable in PDC bits.

This paper presents a new method ofproducing PDC drill bits that reduce oreliminate bit whirl. Traditionally,attempts to design laterally stable PDCbits have assumed that the forces gener-ated by the bit cause it to begin whirling.This new approach assumes that it is theresponse of the bit to force motion off itscenter that causes whirl.

This new method was successfully vali-dated through a field test program in theNorthwest US.

This paper demonstrates how the use ofthis new method can eliminate whirl inboth laboratory and field environmentsand deliver significant performanceimprovements over traditional force bal-ancing methods.

26 D R I L L I N G C O N T R A C T O R January/February 2006

As RSS tools evolve, so should bit designs

IADC/SPE DRILLING CONFERENCE: DRILLING OPTIMIZATION & BITS

98986: Traditionally, attempts to design laterally stable PDC bits have assumed that the forces gen-erated by the bit cause it to begin whirling. A new approach assumes that it is the response of thebit to force motion off its center that causes whirl. A test in the Northwest US validated the method.

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A New Method of Producing LaterallyStable PDC Drill Bits (IADC/SPE 98986)SC Johnson, ReedHycalog.

G A G E P A D D E S I G N S

Although several factors affect overall bitperformance, this paper will isolate thecontributions of gage pad design as theyrelate to the functionality, dynamicbehavior and performance of the differ-ent rotary steerable tool types: push-the-bit and point-the-bit. It will discuss theeffects of gage pad length, geometry andactivity (side cutting) when all other bitfactors are held constant.

Extensive field data having differentgage configurations and in similar appli-cations will be presented.

Gage Design Effects of Gage PadLength, Geometry and Activity (SideCutting) on PDC Bit Stability, Steer-ability, and Borehole Quality inRotary Steerable Drilling Applica-tions (IADC/SPE 98931) G Mensa-Wilmot, B James, Smith Bits; L Aggarw-al, H Luu, Schlumberger; F Rueda, BP.

D R I L L I N G S I M U L A T O R S

This paper describes how the use of afull-size, real-time drilling simulator cansignificantly reduce the learning curvefor operations.

Techniques such as Through TubingRotary Drilling (TTRD) and ExtendedReach Drilling are still typically new tomany of the field drillcrews involved.

Traditionally used for well-control train-ing or the training of crews to operatenew-generation automated drillingequipment, drilling simulators are alsonow being used to practice techniques ina low-cost environment.

This paper describes how state-of-the-artsimulators can be programmed to realis-tically model the proposed operation.

The paper explains how well plannerscan then identify whether certainaspects of their programs are effectiveand establish whether all anticipatedeventualities have been covered.

The paper concludes that the use of suchfacilities has significantly acceleratedthe learning curve experience whendeveloping innovative well programs.

Reducing the Learning Curve ThroughUse of an Advanced Drilling Simula-tor (IADC/SPE 98107) RK Hodgson, SPorteous, P Hassard, KCA DEUTAGDrilling Ltd.

N O R W E G I A N T R O L L F I E L D

In 2001, an innovative service wasintroduced to the Troll Field Reservoirin the Norwegian North Sea, beingfounded on a new multisensor dataacquisition and processing Measure-ment While Drilling (MWD) tool. Thedownhole tool contains variousdynamics and mechanical sensors anda high-speed data processing systemto continuously provide an accuratepicture of downhole conditions andthe energy transfer train. This real-

time service, as well as the intrinsicdetailed studies on BHA and bit designwith ensuing in-depth knowledge cap-ture, have lead to a comprehensiveunderstanding of the Troll drillingchallenges and thereby facilitated thedesign and utilization of application-specific bottom-hole assemblies.

This paper will discuss how this technol-ogy is used and how this total drillingsystem deployment concept was appliedto successfully surmount the specificchallenges of the Troll Field.

IADC/SPE DRILLING CONFERENCE: DRILLING OPTIMIZATION & BITS

January/February 2006 D R I L L I N G C O N T R A C T O R 29

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Mitigating Application Specific Chal-lenges Through a Total SystemApproach (IADC/SPE 99122) MStavland, Baker Hughes; H Wolter, HydroOil & Energy; JG Evans, Baker Hughes.

DRILLING THE BUNTER

The Middle and Upper Bunter formation(Triassic) in Northwest Germany is avery hard and abrasive formation, typi-cally in a depth range of 8000 ft to 12,500ft. It consists of layers of quartzitic sand-stone and silificated claystone. Low ROPand high abrasive wear of tools is char-acteristic for drilling this formation. Toimprove the performance and decreasecost/ft, intensive research was done inthe past.

This paper deals with the results of theanalysis of historical data and the devel-opment of bits, motors and other BHAcomponents to a total system. This BHAsystem is to enhance ROP and reducetrips due to dull bits or BHA and drill-string failure.

To date, 15 runs of these improved BHAsystems have been performed. Perfor-mance data have been analyzed and willbe presented to document achievedimprovements.

ROP Enhancement In Ultrahard Rock(IADC/ SPE 99045) M Roehrlich, KBelohlavek, ExxonMobil.

CUTTING ROCK INTERACTION

PDC drill bit design is generally done bybalancing the bit, distributing uniformwear along the profile and achieving highdrillability and control steerability. Drillbit designers adjust features such as pro-file shape, gage and mainly cutters char-acteristics.

Cutter rock interaction model becomesa critical feature in the design process.But previous models considered onlythree forces on the PDC: drag force,normal force and side force. Such mod-els are no longer valid with the intro-duction of PDC cutters with chamferand special shape.

This paper presents a new cutter rockinteraction model with several improve-ments.

First, it is based on the presence of abuild-up edge of crushed materials onthe cutting face often described in the lit-erature but never modeled. Secondly, thechamfer, which significantly affects bitROP, is completely modeled with its

shape and size influence. Third, forcesapplied on the back of the cutter and dueto the rock deformation and back flowcrushed materials are taken intoaccount. Finally, numerous single cuttertests are shown to validate the new cut-ter rock interaction model and investi-gate the influence of the PDC character-

istics. The model has been applied tooptimize the cutting efficiency and bitsteerability.

PDC Bits: All Comes From the CuttingRock Interaction (IADC/SPE 98988) LGerbaud, S Menand, H Sellami, ParisSchool of Mines. �

30 D R I L L I N G C O N T R A C T O R January/February 2006

IADC/SPE DRILLING CONFERENCE: DRILLING OPTIMIZATION & BITS

98988: Electronic microscope view of chip formation used to develop a new cutter-rock model.

98107: Drilling simulators — tra-ditionally used for well-controltraining or the training of crews tooperate new-generation automateddrilling equipment — are nowbeing used to practice techniquesin a low-cost environment withthose tasked with onsite execu-tion. State-of-the-art simulatorscan be programmed to realisticallymodel the proposed operation,with emphasis on well challenges.

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