Stinger

Conical diamond element

StingerApplications

Wide variety of formation types and compressive strengthsRotary, motor and rotary-steerable drive systems and anyBHAconfigurationVertical, build, and lateral drilling

Benefits

Enhances drilling efficiency for greater ROP

Increases bit stability and decreases vibration

Increases bit durability to minimize bit runs

Produces larger cuttings for more accurate formation evaluation

Features

1

Unique conical shape produces increased point loading tofracture rock more efficiently

Synthetic, ultrathick diamond material layer increases durability

Center-placed cutting structure enhances rockdestruction

Design integrates into a wide range of PDC bit sizes and types

Beyond shearperformanceThe Stinger* conical diamond elementprovides an innovative cutting structureenhancement that significantly increasesa PDC bits performance. Located at thebits center, the element enables high-pointloading to fracture rock more efficientlyfor increased durability and ROP acrossa wide range of formations and operatingparameters. When compared with standardPDC bits in durability tests, PDCbits witha Stinger element demonstrated improvedresistance to wear and impact.

In field tests comparing conventionalPDC bits and PDC bits fitted with aStinger element across a wide range ofrock types and operating parameters, bitswith a Stinger element demonstratedgreater durability and stability whileincreasing ROP as much as 46%.

2

3

Technology answers drillbit performance challengesRESULTSEVALUATIONSIMULATIONDEVELOPMENTCHALLENGE

Improve PDC bitperformance:

Fail rock moreefficiently at bitscenterEliminate cored outdull condition toextend bit lifeDrill efficiently ina wide range offormations

Enhance cuttingstructure at bits center:

Undertake modelingwith IDEAS* integrateddrillbit design platform:

Innovative conicalcutting elementUltrathick syntheticdiamond layerPDC bit cuttingstructureadaptability

tinger elementsScenter placementincreases lateralstabilityROP improvementsthrough increasedrock failing efficiency

Conduct extensivelaboratory testing:

Measure increasedstability andboreholequalityChart enhanced rockremovalAnalyze largercuttings

PDC bits withStinger element vs.conventional PDC bits:

Increased ROP asmuch as 46%Improved cuttingstructure durabilityMinimized bit runs

Borehole center challenges conventional PDC bitsCutter force and velocity plot for conventional 8.75-in, 6-blade PDC with 16-mm cutters1

10.9

Highest-load cutters

0.8

0.8

0.7

0.7Relative cutter force

0.6

0.6

0.5

0.5

0.4

0.4Relative cutter velocity

0.3

0.3

0.2

0.2

0.1

0.1

0

Normalized cutter velocity

Normalized cutter force

0.9

A common challenge to conventional PDC bitsis that they are inefficient at removing rockfrom the center of the borehole. Because therotational velocity of cutters decreases withtheir proximity to the center of the cuttingstructure, rock removal by the center-mostcutters is much less efficient, especially inhard formations.Because the center cutters bear the highestload, operational and formation changescan cause large variations in depth of cut,inducing bit torque fluctuations. This resultsin decreased drilling efficiency at the centerof the bits cutting structure, which can causelow rates of penetration, destructive lateralvibrations, and cutter damage.

00

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Distance from bit center, inPlot shows typical forces and cutter velocity, from the bit center to the gauge. The center-most cuttersexperience the highest loads and have the lowest rotational velocity, subjecting them to more stress andmaking them lessefficient.

5

CHALLENGE

DEVELOPMENT

SIMULATION

EVALUATION

RESULTS

Center-placed element increases PDC efficiencyTo decrease damage and increaseperformance at the center of a PDC bitscutting structure, bit design engineersconceived a center-placed conicaldiamond element.To position the element in the bit, engineersremoved the center cutters. The absenceof these cutters allows a stress-relievedcolumn of rock to develop while drilling,which continuously fractures and crushes,thereby improving drillingefficiency.

With conventional PDC bits, cutters extend from thecenter of the bits cutting structure to the gauge.

CHALLENGE

DEVELOPMENT

SIMULATION

Removal of the PDC bits centermost cutters wasrequired to accommodate a center-placed conicaldiamond element.

EVALUATION

RESULTS

6

Conical diamond element advances rock destruction

Stinger Element

The Stinger element produces a crushingaction as opposed to the action of traditionalsynthetic diamond cutters and inserts used inPDC and roller cone bits.

7

CHALLENGE

PDC Cutter

Positioned on bit blades, the higher velocityPDC cutters are optimized to effectivelyshear the formation and ensure bottomholecuttingefficiency.

DEVELOPMENT

SIMULATION

Diamond Enhanced Insert

The diamond enhanced inserts (DEI) are usedon the gauge and heel row of roller cone bitsto ensure gauge hole integrity.

EVALUATION

RESULTS

Proven materials engineered to extend bit durabilityStinger element

PDC

DEI

1.00

Relative scale

The Stinger element has twice the diamondthickness of conventional PDC cutters andis manufactured from synthetic diamondmaterial engineered to provide impactstrength and superior resistance to abrasivewear. Combining this capability with theStinger elements unique conical geometryresults in a cutting element that significantlyincreases a PDC bits durability.

0.75

0.50

0.25

0

Wear resistance

Impact strength

Diamond thickness

In tests, PDC bits with a Stinger element demonstrated greater wear resistance and impact strength propertiesthan PDC bits fitted with conventional cutters or rock bits fitted with DEIs. The Stinger element has a syntheticdiamond layer that is significantly thicker than that of a conventional PDC cutter or DEI.

CHALLENGE

DEVELOPMENT

SIMULATION

EVALUATION

RESULTS

8

IDEAS design platform optimizes elements placementTo ensure that the Stinger elementsincorporation into a PDC bit would maximizedrilling efficiency, engineers used IDEASintegrated drillbit design platform to improvea PDCs cutting structure in two major ways:They shortened the blades that held the PDCbits low-velocity center cutters and placedthe Stinger element at the center of the PDCbits cutting structure.To measure the effectiveness of adding aStinger element to a reconfigured PDC bitscutting structure, IDEAS platform simulateddrilling was conducted in shale, limestone,and sandstone. In these tests, PDC bitswith aStinger element demonstrated ROPincreases of asmuch as18%.

By reconfiguring the bit with the Stinger element, a column of rock is allowed to form at the center of thecutting structure, which is continuously fractured and crushed, increasing drilling efficiency.

9

CHALLENGE

DEVELOPMENT

SIMULATION

EVALUATION

RESULTS

Advanced modeling tools enable cutting structure optimizationFEA modeling

Using finite element analysis (FEA) modelingsoftware, engineers analyzed the precisepoint at which the Stinger element tip indentsa rocks stress field.The analysis showed that significantly lessapplied load is required to fracture rock, if theload is concentrated at a single point.

FEA modeling software was used to study fracturingmechanics at the point the Stinger element tipindents the rock.

CHALLENGE

The effect of this single-point loadingis compounded with a Stinger elementbecause the column of rock that the bitallows to develop is isolated and therebyunconstrained, making it easier to destroy.This effect has also proven to increasestability and reducevibration.

Precise nozzle placement for cleaningPlacing the Stinger element in the center ofthe cutting structure makes it essential thatnozzle orientation and the resulting flow fieldare optimized. This will ensure the Stingerelement is efficiently cleaned and cooled.

A detailed hydraulic analysis was undertakenusing advanced computational fluid dynamic(CFD) software to accurately simulate theflow around the Stinger element. In thecourse of each new bit development, nozzlepositions are adjusted and finely tuned tomaximize cleaning of the Stinger element andthe bottom hole around the bits center.

DEVELOPMENT

SIMULATION

Optimized nozzle placement showing cross flowpathlines and higher fluid velocity for enhancedcleaning and cuttings removal.

EVALUATION

RESULTS

10

Bottomhole evaluation confirms increased rock failing efficiencyIn a controlled test, a standard PDC bitand a PDC bit with a Stinger element weresubjected to downhole confining pressuresand evaluated to identify the bottomholeprofile of each.The bit with the Stinger element produceda highly developed rock column at the verycenter of the bit that mirrored its cuttingstructure. The rock column clearly showedevidence that it was being fractured,confirming that the conical diamond elementwas crushing the rock into larger-thannormalfragments.

Bottomhole profile generated by conventional PDC bitin the test (above) and IDEAS simulation (below).

11

CHALLENGE

DEVELOPMENT

SIMULATION

Bottomhole profile generated by PDC bit withStinger element in the test (above) and IDEASsimulation (below).

EVALUATION

RESULTS

Increased geological evaluation accuracyPDC bits with conventional cutting structuresdrill by scraping and shearing rock, whichproduces cuttings that are often too small foraccurate formation evaluation.A PDC bit with a Stinger element deliversa crushing action, causing much largercuttings to splinter from the rock column thatis created. The resulting larger fragmentsenable wellsite geologists to determinemore accurate rock properties for reservoircharacterization and wellbore placement.

0

1

2

3

cm

0

1

2

3

cm0

1

in

0

1

in

When cuttings collected from a drilling simulator were compared, those generated by a conventional PDC bitwere smaller (left) than those produced by a PDC bit with a Stinger element (right).

CHALLENGE

DEVELOPMENT

SIMULATION

EVALUATION

RESULTS

12

Greater stability for improved borehole quality

The stability demonstrated by bits with aStinger element is a positive dynamic, whichimproves borehole quality and reducesstress on drillstring components, increasingBHAreliability.

0

0

0.5

0.5

1.0

1.0

Depth, ft

The test was run in hard-medium grainedsandstone with a unconfined compressivestrength (UCS) of 9,000 psi. Bit revolution wasmaintained at a constant 85 RPM on both bitsto control variance. The borehole drilled bythe PDC bit with a Stinger element showedthe least amount of hole diameter variance,which is reflective of a more stable cuttingstructure design that is less vulnerable tolateral and torsional shocks and vibrations.

Depth, ft

A test was conducted to compare boreholequality produced by a conventional PDC bitversus that of a PDC with a Stinger elementwhen changes are introduced to weight on bit.

1.5

1.5

2.0

2.0

2.5

2.5PDC bit with Stinger elementConventional PDC bit

3.00.02

0.04

0.06

0.08

0.10

Hole-diameter variance, in

13

CHALLENGE

DEVELOPMENT

SIMULATION

3.0

0

4,000

8,000

Weight on bit, lbf

EVALUATION

RESULTS

12,000

14

Case Studies

SHARC Bit with Stinger Element Increases ROP 46% inNorth Dakotas Bakken FieldHard formations challenge bitdurability and ROP

To increase ROP and reduce the numberof bits used by operators drilling 8-invertical sections in the hard, abrasive, andinterbedded formations of North DakotasBakken basin, Smith Bits added a Stingerelement to a standard SHARC* PDC bit,creating the MDSiZ616.

15

CHALLENGE

DEVELOPMENT

SIMULATION

Stinger element significantly advancesdrilling performance

SHARC PDC bits were fitted with 16-mmcutters and a Stinger element; the bits wererun on a directional BHA and drilled 8-invertical sections of between 6,209 and 6,477ftin single trips. Bits attained an average ROPof 168 ft/h that included a record run with anaverage ROP of 203 ft/h. When comparedwith the next best average ROP reported byother bits in offset wells, the SHARC bits witha Stinger element increasedoverall averageROP 46%.

EVALUATION

RESULTS

Company A,average

Company B,average

MDSiZ616,average

MDSiZ616,record run

1,000

203

2,000168

175

Depth, ft

4,000

150115

5,000

7,000

225200

3,000

6,000

250

976,583

125100

876,301

6,669

6,301

6,318

75

8,000

50

9,000

25

10,000

0Smith Bits baseline bit

CHALLENGE

SHARC bit with a Stinger element

DEVELOPMENT

SIMULATION

Other bits

EVALUATION

ROP, ft/h

0

MDSi616,average

When compared withthe next best averageROP of 115ft/h byother bits, the SHARCPDC bits with aStinger element drilledNorthDakotas Bakkenbasin at an averageROP of 168ft/h thatincluded a record runwith an average ROPof 203 ft/hr, which isan overall increase inaverage ROP of 46%.

ROP, ft/h

RESULTS

16

Case Studies

PDC Bit with Stinger Element Increases ROP 14% inUtahs Wasatch FormationChallenging applicationdemands durability

The lithology associated with applications innorthern Utahs Wasatch formation consistsof difficult interbedded sand and shale withUCS that ranges from 2,000 to 30,000 psi.For this application, a 778-in, MiZ616 PDC bitwith a Stinger element was selected. Theassembly was run on a directional BHA usinga positive displacement motor (PDM) witha 1.5 bend angle with the following goals:Increase ROP, improve cutting structuredurability in high weight-on-bit applications(30,000 to 50,000 lbf), and reach section TD inone run.

17

CHALLENGE

DEVELOPMENT

SIMULATION

Stinger element enhanced PDCdelivers increased durability and ROP

The PDC bit with a Stinger element drilled6,050 ft of the 778-in wellbore to TD in one trip.The bit was pulled in excellent dull condition:1-2-BT-C-X-IN-WT-TD. When comparedwith four bits that reported the highest ROPaverages in offset wells, the PDC bit with aStinger element increased ROP 14%.

EVALUATION

RESULTS

MDSi616

Mi616

Mi616

Company A

Average

1,000135

MiZ616

141

134

Depth, ft

2,0003,0004,000

117

109

180150120

124

90

3,7924,402

5,000

5,778

6,000

60

4,770

5,109

6,050

7,000

When compared with bits that hadthe best average ROP in four offsetwells, the PDC with the Stinger elementdelivered a 14% greater ROP withincreased footage.

ROP, ft/h

0

300

Case study bit

CHALLENGE

Smith Bits without Stinger element

DEVELOPMENT

Other bits

SIMULATION

ROP, ft/h

EVALUATION

RESULTS

18

ReferenceNomenclature

A PDC bit equipped with the central Stingerconical diamond element is identified by theletter Z in the bit type, directly before theblade count and cutter size.

Dull grading

The unique conical geometry of the Stingerelement requires a modified dull gradingsystem, in order to measure the amount ofdamage observed (lost, worn, or broken). Thewear rating scale (0 to 8) is the same, as usedfor standard PDC cutters.

Stinger element dull grade examples

0 (0% wear)4 (50% wear)8 (100% wear)

Examples

MDSiZ616

SDiZ513

MiZ613A wear card for field use is availablefrom SmithBits to accurately measurewear of the central Stingerelement.

19

Stinger element with 0 rating (0%) wear; no signs ofwear orchipping.

20

StingerFind out more about the Stinger conical diamond element atwww.slb.com/Stinger.Animation

See the advanced rock destruction efficiency the Stingerelement gives a PDCbit.

Case Studies

SHARC PDC bits with a Stinger element drilled 8-in verticalsections in North Dakotas Bakken basin in single trips,which included a record run with an average ROP of 203ft/h. This surpassed the average ROP reported by other bitsin offset wells by 46%.

ONYX II

PDC cutters with greaterwear resistance anddurability to maximize ROPwww.slb.com/ONYXII

IDEAS

Integrated drillbitdesign platformwww.slb.com/IDEAS

A PDC bit with a Stinger element drilled a 6,050-ft, 778-inwellbore through Utahs Wasatch formation in one trip witha 14% higher ROP and was in excellent dull condition.

www.slb.com/Stinger

*Mark of SchlumbergerOther company, product, and service names are the properties of their respective owners.Copyright 2013 Schlumberger. All rights reserved. 12-BT-0091