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• 3.1 API Scope of specifications 4• 3.2 API Drill Pipe mechanical properties 5-6• 3.3 API Limitations 7• 3.4 BHA component specificity 8• 3.5 Development Areas 9

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• 4.1 Evaluation Criteria 11

• 4.2 API Connection 12

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• 5.1 NKK Double Shouldered Tool Joint 13

• 5.2 GRANT PRIDECO High Torque connection 14

• SST 14• HT, HI-TORQUE 15-16• XT, eXtreme Torque 16

• 5.3 HYDRIL, Wedge Thread 17-18

• 5.4 DBS, Slim Hole series 19

• 5.5 OMSCO, Tuff Torque 20-21

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• Connections data – Comparison Table 23

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• Appendix 1 : Thread Form 26

• Appendix 2 : Drill Pipe Design 27

• Appendix 3 : Make Up Torque 28

• Appendix 4 : Drill Pipe Management 29

• Appendix 5 : Stiffness Ratio 31

• Appendix 6 : Methodology - Torque 31

• Appendix 7 : Methodology - Hydraulics 32

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The aim of this study is to perform a technical review of available High Torque connections for drill pipesand to present their advantages and drawbacks compared to API connections.

A substantial increase of complicated wells (3D, ERD, complex trajectory) is noticeable; Fifty percent ofdevelopment wells drilled by TOTAL are now horizontal which is a major step change compared to wellsdrilled ten years ago.

Drilling engineers shall use the proposed guidelines to select the best drill pipes corresponding to local andeconomical environment.

Amongst considerations that influence the planning and preparation of challenging wells, a bulk list (1) canconsist of the following parameters:

• Drill pipe in terms of maximum yield stress, make-up torque, fatigue resistance• Drag or axial friction during sliding operations• Contact Loads, riser and casing wear• Top Drive System, its maximum sustainable torque• Stuck pipe and maximum applicable overpull• Buckling under high compressive loading• Hydraulics, maximum standpipe pressure, hole cleaning• Equivalent Circulating Density, pore pressure and fracture gradient• Wellbore stability, borehole collapse, loss circulation• Inspection, repair• Logistics, total length of drill pipes that can be handled, large volume of mud

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On one hand, pressure losses along the drillstring and in the annulus limit hole cleaning, especially inhighly deviated wells where cuttings tend to settle on the low side.

On the other hand, torque and drag are affected by well trajectory and friction factor.

Despite many effort in optimising well trajectory by minimising well bore tortuosity and dog legs, in reducingfriction factor with torque reducers, mud additives, drill pipe hardbanding, it is not always possible to staywithin operating torque of conventional drill pipes. If standard connection cannot be pushed above currentlyrecommended torque capacity, higher torsional yield strength drill pipes are then necessary to transmitenough torque to the bit.

A review of connections improvements through years is necessary to get a comprehensive understandingof the final drill pipes evolution to meet industry requirements.

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First wells drilled in 1859 in Pennsylvania by Uncle Billy, Colonel DRAKE toolpusher, were performedpercussion drilling with cable. It worked fine as long as drilling operations took place into hard andconsolidated formation.Hammer drilling appeared later on in Canada required both the use of pipe and mud circulation.FAUVELLE (France) had originally introduced that technique for water wells around 1845. Connectionsbetween pipes had to be tight. Torque was applied on a thread taper. Rotary drilling (1901) was developedto overtake low penetration rate encountered into sticking shale and unconsolidated sandstone in Texas.The torque was applied on a shoulder giving birth to the rotary shouldered connections. This principlerapidly became a standard and so was called “Regular”. But in those early days, it was difficult to be surethat drill pipes or drill collars of any given manufacturer would match: threads would not always mate andwall thickness could be different. American Petroleum Institute (API) committee for pipe standardisationwas founded around 1926's to clarify specifications, avoid confusion and standardise pipes.

During the late 1920's highly competitive drilling was done in new oil field of Oklahoma and much troublewas experienced with crooked holes and drill pipes failures in tool joints. Initially tool joints were threaded ateach end just like couplings. Weld on tool joints were introduced and range 1 (20 feet long) drill pipes weresubstituted by range 2 (30 ft) thus eliminating about one-third of potential weak points. Improvements inrotary drilling system led to deeper targets resulting into hydraulics considerations due to increasingpressure losses and mud flowrate.

Throughout the early 1930's new developments and designs were employed in an effort to eliminate failureof drill pipe threads. Two new ideas were introduced:

• Introduction of welded tool joints on drill pipes and• Running drill pipe in tension versus compression

In the 1930's, appeared Full Hole (FH) connection for tool joint. Inside Diameter of a 4 ½ FH increasedfrom 2 ¼ to 3” and Outside Diameter from 5 ½ to 5 ¾” compared with 4 ½ Reg.The thread form is a V profile. Both root and crest are truncated. The width of flat at crest truncationcompletes its definition. FH thread form was chosen either V-040 or V-050 as already used for regular. Theroot of the thread is rounded and this root radius is either 0.020" or 0.025".

In the early 1940’s the Internal Flush (IF) connection was created in an attempt to minimise pressure lossesthrough drill string. New dimensions available were from 2"3/8 to 5"½ but with a new V-065 thread profile.

This V-065 thread form has been applied on other connections such as "X-HOLES", "OPEN-HOLES","WIDE-OPENS", "EXTERNAL FLUSHES", "DOUBLE-STREAMLINE", "SEMI-INTERNAL FLUSHES". Mostof them are obsolete now. Connections still in use are IF and PAC.

Thread Form : V-040/V-050

Thread Style : REG-FH

Thread Form : V-065

Thread Style : IF-PAC

Radius0.020 "or 0.025"

Truncation0.040"

0.015"Truncation0.065"

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During World War II, material mechanical behaviour knowledge has improved. Concerns about stressconcentration and scored places on thread are since then taken into account. Use of treated Chrome-molybdenum steel has generalised. Seamless steel drill pipe is now offered in four grades of steel (E75, X95,G105 and S135) compared to grade D55 (55,000 psi yield point) used in 1928.

In the 1960’s a milestone in drill pipe connection was introduced with the HUGUES H90 : scored placeswere opened so that thread contact increased from 60 to 90° and a flat area inserted in between two radius(0.025”) in the thread;

REED introduced the “high flexing” ” to pre-stress the steel and enhance connection fatigue resistance. Itsprocess consisted of cold-hammering the thread roots. The use of a pneumatic hammer generated facetsand irregular pre-stress. HUGUES designed the “Cold Rolling" of a much reliable process.

H-90 worked reasonably well till API profile V-065 was replaced by V-038R on IF connection giving asimilar resistance to fatigue and being interchangeable with old V-065 profile. Indeed 9����5�LV�DOVR�D�9W\SH�SURILOH�ZLWK�D��������IODW�ZLGWK�EXW� WKH�URRW�UDGLXV� LV�������. "R" meaning cold rolling has beenapplied. Cold Rolling is more beneficial on BHA elements tool joints which suffer more of fatigue than drillpipes owing the relative stiffness of the tool joint compared to the tube.

This thread form remains an API standard and is still applied on some High Torque connections as well(See appendix 1).

Rotary drilling imposed itself since World War II. Rotary shouldered connections have been evolvingthrough years and each time a new model was introduced every effort was made to keep the newinterchangeable with the old.

Main connections still in use are :

• "REGULAR" (Reg) especially for BHA components,• "FULL HOLE" (FH) officially reinstated in 1993 and popular for 6"5/8 drill pipe,• "PAC" for 2"3/8 and 2"7/8 drill pipes (They are definitely not recommended for drill collars due to their low tensile and torsional capacity), as they afford a good fishing ability with overshot when, for example, cleaning 4"1/2 liner,• "API Numbered Connections " (NC XX) which is industry current standard.

30°0.038"

Thread Form : H-90

Thread Style : H-90

Thread Form : NC - HT- DSTJ

Thread Style : V-038R

Radius0.025"Flat area

Crest truncation0.065"

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American Petroleum Institute provides some specifications and recommended practices for the entireOil&Gas industry which are briefly described in this chapter. (For more information, one should referdirectly to API 5D and 7)

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API Specifications list definitions and tolerances about drill pipes range (1,2,3), connection (NC) and grade(E, X, G, S) in mainly vertical holes applications.

• API 5D characterises the tube body only in terms of Yield and Tensile Strength, ductility, toughnessand internal upset geometry.

• API Specifications 7 and RP 7G list dimensional data for drill string assemblies and recommendedpractices for the handling of drill pipes and tool joints. It deals with the tool joints, drill collars, subs, kellyand safety valves (& IBOP’s) in terms of Yield and Tensile Strength, ductility only.

• Heavy Weight Drill Pipe, stabilisers, motors, MWD, jars, etc are not covered by any API specifications.

• API definition of a drill pipe is a length of tube, usually steel, to which threaded connections called tooljoint are attached. A rotary shouldered connection is described as a connection used on drill stringelements which has coarse, tapered threads and seating shoulders designed to :

• sustain the weight of the drill stem (traction, compression),• withstand the strain of repeated make-up and break-out,• resist fatigue (flexion),• resist additional make-up during drilling (torque),• and provide a leak proof seal (pressure).

• API introduced the equivalent Numbered Connection (NC) in API 7 in 1968.There are 17 designations from NC 10 (1"1/16) to NC 77 (7"3/4).

NC stands for Numbered Connection and the number (XX) is fixed by the Gauge PointPitch Diameter (GPPD at 5/8” below the shoulder) multiplied by 10. For a long time APISpecifications 7 have had no specifications on taper angle. (see figure 3.1)

Hardfacing

Weld

Pipe Body External Upset

Tool Joint

Pin

Internal Coating

Elevator Shoulder

Internal Upset

Box

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Despite API definition, the industry is still calling a connection by a name not corresponding anymore to itsdesign description:

Original 4”1/2 IF Actual 4”1/2 IF or NC50Tube Outside Diameter 4”1/2 5”Tube ID shape with Internal Flush upset with Internal UpsetThread form V-065 V-038R

The above example illustrates that what is called “4 ½ IF” corresponds actually to 4"1/2 OD drill pipe withan Internal Flush upset type and a V-065 thread form connection. This one has been replaced by asmoother, more fatigue resistant root: its thread form is V-038R and it has an internal upset. So what wecall a 4”1/2 IF connection should be properly called according to API designation 5” NC 50, 5" being drillpipe OD.

Now all API connections from NC23 and above have four V-038R thread with 2 in/ft taper.Seamless drill pipe is upset to API dimensions for weld-on tool joints in three types : Internal Upset (IU),External Upset ( EU) and Internal-External Upset (IEU).

Nearly every obsolete connection has been replaced by a NC equivalent. Most commonly used NCconnections are:

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2 3/8 Internal flush2 7/8 Slim Hole

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1&��(4.6260")

4 Internal flush4 ½ Extra Hole

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3 ½ Internal flush4 ½ Slim Hole

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4 ½ Internal flush5 Extra Hole5 ½ Double Streamline

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The four basic causes of drill pipe failures are as follows:

• Tool joint and tube OD wear• Internal corrosion• Fatigue cracking in the slip and internal upset areas,• Physical damage to the tool joint threads and shoulders, and to the tube.

Several studies confirmed that washouts occurred near the end of the internal upset (noted Miu) closest tothe tube body, the most highly stressed area of the drill pipe during drilling and the most prone to fatiguefailure. Up to now fatigue phenomenon are not fully understood and research programmes are still ongoing. BHA components are more prone to fatigue mode failure at connection than drill pipe.

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The Tensile Strength of drill pipe (based on minimumvalue) is used to determine useful working depth for aparticular grade of pipe. To reach greater depth, highergrade with greater strength pipe should be used except insour environment unless corrosion control is added inmud and high pH is maintained. The minimum TensileStrength determines the minimum parting load in torsion,tension, burst and collapse of the drill string components(plastic deformation area).

Steel Grade Minimum Tensile Strength (psi)E 75 75,000X 95 95,000G 105 105,000S 135 135,0007RRO�-RLQW �������Drill Collar 110,000 (3"1/8 <OD< 6"7/8)

Drill Collar 100,000 (7" <OD< 10")

All API drill pipes tool Joints are made from the same material with a minimum Yield strength of 120,000 psi.

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Drill pipe tool joints are normally weaker in torsion than the tube they are attached to. Neverthelesstorsional capacity of both tube and tool joint must be checked and the lower value will determine torsionalcapacity. The torsional yield strength is the resistance to failure due to the application of a twisting force.

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API sets an arbitrary ratio (noted TSR) of 80% between tooljoint’s and tube’s torsional yield strength to define standardtool joint OD and ID.In other words, tool joint OD and ID determine tool jointtorsional capacity. The greatest TSR reduction occurs with ODwear. FPL recommends applying hardbanding on tool jointthat not only protect the drill string but that are also casingfriendly.An eccentric correction factor ()) is applied in case drill pipe is worn eccentrically.

Torsional strength is a function of several variables including the strength of the steel, connection size,thread form, lead, taper and coefficient of friction on mating surfaces, threads or shoulders. It isindependent of tube grade.

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FARR was a HUGUES Tools engineer. Its formula resultedfrom observing drill collars connections mix-up on a rig site. Itemphasises on threads deformation due to make up torqueand shows that lead of thread has little to do comparing withfriction in the thread or against the shoulder. This explainsspecial care brought into dope selection.In this formula the cross section area defines whether theconnection is "pin or box weak". If the pin controls when new(pin weak, pin cross section area is smaller), some OD wearmay occur before torsional strength is affected. At whateverpoint the tool joint box area becomes the smaller, any furtherreduction in OD causes a direct reduction in torsional strength.

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Calculations for recommended makeup torque for rotary shouldered connections is the amount of torquerequired to achieve a desired stress level in the weaker member, pin or box. For a standard connection thistorque amounts 60 % of minimum tensile yield strength for tool joint material conforming API 7.

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Makeup torque is independent of the grade of the pipe. For a long time makeup torque have not beenmeasured accurately at the rig site. The maximum surface torque is considered to be tool joint makeuptorque as tool joints are normally weaker in torsion than the tube.

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0DNHXS� WRUTXH� FDQ� EH� LQFUHDVHG� DERYH� VWDQGDUG� YDOXH� EXW� FRPELQHG� 7HQVLRQ�7RUVLRQ� ORDGFDSDFLW\�RI�WKH�WRRO�MRLQW�PXVW�EH�SUHYLRXVO\�FKHFNHG. It means that, at the rig site, if the makeup torquehas been increased, the maximum overpull is decreased otherwise desired stress level is overtaken. Thisway to increase tool joint torsional capacity is called "VWUHVV� EDODQFLQJ" and can be field implementedwhen operational torque and axial loads are estimated with confidence. It is described later in APIconnection evaluation paragraph.

Steel elastic deformation under constraints is not instantaneous. It is necessary to apply make up torqueduring several seconds continuously to store enough energy.To remain tight specially when wobbling occurs a connection should have stored energy : make upstretches the pin and compresses the box shoulder elastically so that connection is kept from leaking, evenwhen bent by high side loads.

In clear, double shouldered connection makeup torque value are :

• Based on a desired stress level within the connection• Independent of tube grade• Dependent of a minimum OD and ID to be checked• Have to be applied according specified operating practices :

½ several seconds to efficiently store enough energy½ respect tongs height½ take into account dope friction factor

• And can be increased after checking combined Tension/Torsion load capacity

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It is necessary to mention that API specifications do not cover every drill stem components and aregenerally conservative.

• $3,�53��*�GRHV�QRW�DGGUHVV�HYHU\�DWWULEXWHV�LPSRUWDQW�LQ�PRUH�FULWLFDO�GULOOLQJ�DSSOLFDWLRQV suchas : hardfacing, extra tong space, anti galling, elevator shoulder, make and break, internal coating, grademarking, slip proof drill pipe, under balance design, short radius drill pipe, pup joints, etc all those itemssometimes merchandised by manufacturers.

• API specifications are not only limited but they are sometimes confusing : A 5" drill pipe 19.5 lb/ft IEUNC 50 Grade E will have an approximated weight of 20.89 lb/ft as 19.5 lb/ft is the nominal weight of thetube alone.

• Another weakness of API recommendations isthat they remain very conservative in defininglimitations related to hole deviation.

• According to the graph showing region of nofatigue damage (See figure 3.3), wells in LIBYA(horizontal multi drains with 16°/100ft) or in the NorthSea ( up to 42°/100 ft on D05) would have neverbeen possible to drill

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• API recommendation for minimum CHARPY toughness on drill pipe tube (40 ft.lbs) is insufficient. Itresulted from CHEVRON and SHELL Canada lobbying; SHELL Canada demonstrated that a minimumCHARPY resistance of 74 ft.lbs was required to ensure drill pipe would sustain a through-wall crackwithout parting ("Leak before Break" concept). API unfortunately followed the other work conclusionsperformed by CHEVRON.

• Current API specifications allow a 12.5%deviation on nominal wall thickness. Somecontractors are pushing to decrease API thistolerance down to 5-6% in order to double theamount of OD wear allowable prior to demotedrill pipe from premium to Class 2 status.

• Finally API RP 7G does not cover the procedures by which the specifications are to be evaluated. DEAProject 74 has published DS-1TM, drill stem design and failure prevention, which is comparable withTEP/DO/FPL recommended standard for inspection.

Among DS-1TM main contribution is Premium class reduced TSR introduction. OD wear is a key factor todistinguish between the 3 classes of used drill pipe (Ref.: Standard DS-1-March 98).

Attribute Premiumclass

Premium Class,reduced TSR

Class 2

Minimum remainingtube wall thickness

≥ 80 % ≥ 80 % ≥ 70%

Maximum slip cut(depth)2

≤ 10 % ≤ 10 % ≤ 20 %

Tool Joint TorsionalStrength3

≥ 80 % 60-80 % ≥ 80 %

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Drill string reliability is affected by these excessive or unspecified tolerances allowed by API standards,specially in wall thickness deviation, control of the length and shape of the Internal Upset (Miu) and theability of the tool joint thread and shoulder to withstand stress.

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The Bending Stress Ratio (BSR) is the ratio of the pin and box area modulus whereconstraints are maximum (Zbox/Zpin).

In a rotary shoulder connection, the pin critical section is pre-loaded at make-up;During bending this pre-load reduces the amplitude of the cycling stress in the pincritical section. The box in this system does not benefit from a reduced stressamplitude, so it is subject to a greater stress range than the pin. Making the bendingstrength of the box greater than that of the pin produces a balanced connection for theconventional shouldering tool joint.

This concept applies only to the fatigue mechanism in bottom hole assembly (BHA) components. TheBending Stress Ratio has no meaning when applied to tool joints on normal weight drill pipe, nor does itrelate to other performance properties of BHA connections.

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The historical target of 2.5 BSR has led the industry to specify a standard range of around 2.25-2.75 asacceptable for BHA components. API RP 7G defines a wider range from 1.9 to 3.2 depending on thedrilling conditions.Experience is giving value to respect. It is risky to drift away from those:

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Should it becomes necessary to change BSR, this can be done by either adding material to the weakermember or removing material from the stronger. From the failure prevention standpoint the first alternativeis preferable. If the BSR is low, higher risk of premature box failure exists. When the BSR is high, it is thepin the weak part. A low BSR will result into swollen or split box, fatigue crack in the boxes at the lastengaged thread.

BSR applies exclusively to BHA connection and Stiffness Ratio (SR) to any section change within the drillstring. Here again experience defines a non-scientific "wild guess value" or rule of thumb: section changemust be kept below a ratio of 5.5 for normal drilling and 3.5 under severe conditions. (See Appendix 5)

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The more challenging drilling conditions, the more stress applied to drill string components.

To relieve stress for a given connection size there are several solutions;• Insert stress relieve features on either pin or box• Extend thread length• Create a new guide at shoulder opposite end.

The first one has been introduced years ago on API connection and the later are the developmentprinciples used by manufacturers. These features extend connection fatigue life by eliminating un-engagedthread root that acts as stress concentrators. They are more beneficial on drill collars than on drill pipe.Dressing a groove is not as easy on the box than on the pin. Machining of the groove on the box cangenerate scores on circumference that are very damaging. Pin stress relief features are not recommendedon connection smaller than NC 38 because they may weaken the connection’s tensile and torsionalstrength and fatigue is often less a problem as on small connections than non-cyclic loads.

DRILCO has designed the bore back box, similar to a basic traversing, which allow a good surfaceroughness. This process is still very popular and should be considered, even on smaller connections, if boxfatigue is occurring. To mention a drawback for 7"5/8 and 8"5/8 reg as thread width is diminished and mightnot be sufficient to hold increased makeup torque under wobbling conditions.

SMFI offers the taper bore that has the advantage to preserve box thread intact.Wedge Thread connections, described below, are not rotary shouldered but employ a different principlefor carrying torsion.In slim hole technology drill pipes are thin, taper angle is low and there is little space for shoulder so thatwhen tightening connections a better alignment and more turns are required.

Maximum fatigue life

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The choice of a connection consists of a compromise between pipe functionality and material ability to holdloads. Outside and Inside diameter are determined by phase diameter hydraulics calculations and fishingclearance. A connection should hold under traction, flexion, when under pressure and allow to transmittorque down hole.

Connection evaluation is performed considering following criteria:

7RUTXH� Operational torque are usually limited by rotary table, kelly, top drive system or drill pipe make uptorque. As an example a TDS 3 will have a limited torque capacity of 32,000 ft.lbs. It is unnecessary toattempt making up a 5" HT 50 G 105 drill pipe (optimum makeup torque is 42,600 ft.lbs for a 6"5/8 OD and3"1/4 ID connection) with this top drive.Make-up torque value should be corrected to integrate dope friction factor.SHELL has developed some finite elements analysis calculations in an attempt to verify torque valuesprovided by manufacturers. Their models confirmed that yield torque specified for NKK, GRANT PRIDECOand HYDRIL are valid.

+\GUDXOLFV� Limitation is introduced by pumping unit’s operating pressure, stand pipe’s pressuremaximum.Pressure losses inside the drill stem limit jetting through rockbit necessary to obtain an effective action onformation. Most annular pressure losses are concentrated at tool joint OD (singular pressure losses). Thisphenomenon generates a significant increase in ECD. It has been quantified on DUNBAR field in the NorthSea(2). A difference between Tool Joint ID and pipe body ID may jeopardise pumping wireline assemblythrough drill stem.

3ULFH� Purchasing or rental of required drill stem equipment can be out of traditional scope of contractspecifications. Economics calculation prior purchasing should include inspection (with its cost, frequencyand level), insurance in case non contractually specified drill string is run and lost in hole.Range 3 drill pipes can be an alternative as they allow gain in makeup or lay down and inspection. Most ofCIS (former USSR) rigs use range 3 or XLR (eXtra Long Range) drill pipe saving about 12% in purchasingcost. Elsewhere in the world only about 20% of drill pipes are of range 3. Latest SEDCO XPRESS will beequipped with a racking capability of 3 singles XLR or 4 range 2 drill pipes.

)LVKLQJ�DELOLW\� There is better chance to get a good grab on a longer box connection. In case of stuckpipe, clearance between tool joint OD and hole diameter should be big enough to run an overshot. 7" tooljoints should be preferred to 7"1/4 for drilling 8"1/2 phase with 5"1/2 drill pipes.

5HSDLU� Racking drill pipe tends to damage pin end. Stabbing deteriorate box. A good connection shouldallow re-cutting a minimum of two times and offer a sufficient tolerance to maintain sealing.

6HUYLFLQJ�� Servicing of a damaged connection locally should limit logistics cost and prevent customsdelays. Operator or contractor, either which ever owns the drill string, must implement audit of licensees.This also applies to hardfacing.

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API connections are commonly used. Its design is pretty basic.• It allows a good fatigue resistance,• It can be repaired all over the world,• It has stress relief features to withstand cyclic bending.• Still it is limited in torque transmission.

API connection are widely used in the industry and they make reference :• Standard are described,• Availability/Delivery are not of a matter as

½ drill pipe manufacturers have some in their catalogue and½ most rental companies have some on their shelves

• Licensees are present worldwide,• Acceptance by every drilling contractors• Cheaper than High Torque connections

API connection relies on a rotary shoulder for its torsional capacity, which isreduced in case of tool joint OD wear. All API tool joints have the sameminimum yield strength of 120,000 psi regardless the type of grade to whichthey are attached. Therefore, RQO\� WKH� WRRO� MRLQW� ER[� 2'� DQG� SLQ� ,'GHWHUPLQH�WKH�PDNHXS�WRUTXH�IRU�WRRO�MRLQWV�

API values for “new” make up torque should be ignored as they are intended forbreak-in only. A tool joint becomes used immediately before going into the holefor the first time. DS-1TM designation is recommended.

For a standard connection the PDNHXS� WRUTXH amounts to 60% of minimumyield strength for tool joint material and FDQ�EH�LQFUHDVHG�LI�QHFHVVDU\�WR����PD[LPXP�LI� WRUTXH�UHTXLUHPHQW� LV�FORVH�EXW�QRW�EH\RQG� WKH�SRLQW�ZKLFKWKH�SLQ�QHFN�LV�ZHDNHU�LQ�WHQVLRQ�WKDQ�WKH�WXEH;

Under combined torsion/tensionloads tool joint can fail due to :

½ Pin Yield due to externallyapplied tension combined withexcessive torque½ Box Yield due to excess torsion½ Shoulder separation/seal failuredue to tension combined withinappropriate makeup torque.

Pushing standard connection makeup by stress balancing should result from some comprehensive engineeringand be supported by wide knowledge of wells drilled in similar environment.

As an example, makeup torque for a 5" 19.5#Grade G NC50 (6"1/2OD - 3"1/4 ID) can be safelyincreased to 34,000 ft.lbs. But a 5" 19.5# Grade SNC50 cannot because the tool joint pin neckwould have less capacity to carry string tensionthan the tube.

Grade Grade G Grade SDrill pipe Tensile Yield 436,150 lbs 560,760 lbsNormal Makeup torque 30,870 ft.lbsConnection Tensile Yield 625,000 lbsNew makeup torque 34,000 ft.lbsNew Connection Tensile Yield 500,000ft.lbs

Normal makeup Torque fromstress balancing

Pin Yield area

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Some example of API drill pipe with NC connections commonly used are listed in the following table:

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2"3/8 1&��� 6,65# G105 3 3/8 1 ¾ 6,880 150,660 4,130 (b)2"7/8 1&�� 10,4# G105 4 1/8 2 13,200 233,150 7,920 (p)3"1/2 1&���13,3 G105 5 2 7/16 22,200 297,010 13,330 (p)3"1/2 1&����15,5# S135 5 1/2 21/4 32,940 451,110 19,760 (p)4" 1&�� 14# S135 6 3 39,230 403,530 23,540 (p)5" 1&���19,5# G105 6 5/8 3 ¼ 51,700 436,150 31,020 (p)5" 1&���25,6# G105 6 5/8 2 ¾ 63,410 580,560 38,040 (p)5"1/2 )+ 21,9# G105 7 ¼ 3 ½ 72,480 482,690 43,490 (p)5"1/2 )+�24,7# S135 7 ½ 3 87,170 704,310 52,300 (p)6"5/8 )+ 25,2# G105 8 ¼ 4 ¾ 86,240 542,450 51,740(p)

API connections have a limited fishing ability due to their large OD.

Good drill pipe management can enhance fatigue life. Appendix 4 lists guidelines to implement at the rigsite.

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DSTJ developed by NKK is a modified API tool joint. It was designed to beinterchangeable with API tool joint what is an advantage: any kind ofaccessories and conventional drill pipe can be used with DSTJ drill pipe.

The external shoulder provides the sealing and the internal one is a torquestop shoulder. Immediately after external shoulder touches, internalshoulder touches (0.15 mm longer box depth than pin length). NKK specifythat the distance between the pin shoulder (primary) and the intersection ofthe pin base diameter with the thread flank at the first point of full threaddepth cannot exceed ½ inch.

This means not much elasticity is available and the connection thatnormally acts in a spring like manner loses part of its stored energy. Soshould the pin end be damaged while racking up drill pipes in derrick, ascontact on both shoulder is nearly simultaneous, connection sealingeffectiveness is limited, risk of leak existing. Re-facing cannot beperformed on the threads since the outer and internal shoulder mustremain within 0.15 mm of their normal distance to perform correctly. If theexternal shoulder contact before the internal shoulders are within 0.15 mmof each other, then the internal shoulder will not take their required torquebefore the external shoulder begin to deform under maximum load. If theinternal shoulder meet first, then there may not be a good hydraulic sealand a washout may result.

In terms of sealability DSTJ is comparable to API.In terms of hydraulics, benefit is limited as this connection remains "heavy"and requires material (wall thickness).

No feedback is available from TOTAL subsidiaries. Information collectedfrom drill pipe rental companies emphasise on following advantages:

• Servicing (worldwide license network)• Repair ( ½" inch lost at re-cut)• Price, about 10% higher than normal API• Easy fishing

In terms of transmissible torque, DSJT offers about 30% maximum highertorque than API conventional for identical connection dimensions or areduction of wall thickness of about ½ inch for similar torque. SHELL hasperformed finite element analysis and their model tends to prove thatallowable torque is probably higher than given by NKK. DSTJ is quitepopular with SHELL and rentals companies as they have experienced notrouble with it.

Stress relieve groove can be added if needed.

In terms of rig operation concerns, running time is similar to API. This canbe significant where rig daily rate is high.

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GRANT PRIDECO has developed several types of connections in its H-series:

• SST, Super Strong Thread• HT, HI Torque®• XT, eXtreme Torque

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SST is based on Van Der Wissen concept, a SHELL engineer who had in the 60's the idea to modify the pitch to allowa better load distribution along the thread. Unfortunately his calculations were not so accurate. So despite aninteresting concept manufacturing process was very sophisticated and was abandoned after two years.Finite Elements Analysis illustrates stress constraints pretty well and it seems interesting to focus on some area: Arough estimate of constrains applied at a normal makeup is 50 kg/mm² maximum.

Zone A: Box maximum circumference stress at about 15 mm fromshoulder and below the surface (1mm) due to friction at shoulder.This is where splitting are generated under hydrogen weakening

Zone B & C: Last engaged thread roots where maximum stress isand overtake elastic limit resulting into a permanent (plastic)deformation.

Zone D: Around 35 kg/mm² under tensile stress

Here instead of modifying the pitch, the taper is changed from 2 in/ft into 1.925 in/ft. The root is also deeper, thethread form being 0.057" against 0.038" for API.

There are only two modifications on the pin, the boxremaining API and consequently interchangeable withstandard.

GRANT pretends a better Tensile load distribution is then obtained along the entire thread, reducing the load atthe last engaged thread thus enhancing connection fatigue resistance.

Actually load distribution along the thread has been calculated with FiniteElements Analysis leading that within a API connection first threads areplastically deformed and do not diminish fatigue resistance: a variablepitch thread is obtained. This explains stand off modification after firstmakeup.Still it seems a gain in stress concentration is obtained but it becomesminimal if cold rolling is applied (0.38R) on drill pipe connections, fatiguebeing a relatively rare failure. Because the connection is so much stifferthan the tube, most of the bending and fatigue damage in drill pipe occursin the tube, and thus the advantage of the longer thread root in a SSTtool joint connection could be considered questionable.

SST larger thread root radius would be most beneficial in BHA components.

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HT, HI TORQUE was originally designed by HUGUES (H90) in 1984and is based on a double shoulder connection. When GRANT TFWacquired the tool joint division of HUGUES Tool Company in 1990, itwas included into the H-SERIESTM package.

A primary external shoulder serves as a connection’s sealingsurface. A secondary internal shoulder (on the pin nose) offersadditional friction surface and provides an additional mechanicalstop. Primary shoulder gets into contact first and from a definedtorque secondary shoulder too. Initial clearance (between 0.6 to 0.8mm for HT 50) is compensated by elastic deformation of extendedcounterbores at pin base (about 2" long), pin nose and box (1" long).This allows a proportioned repartition of contact forces between thetwo shoulder surfaces.

Transmissible torque is comparable with NKK’s DSJT but the energystored within the connection is much higher meaning connectionbehaviour under wobble is better. HT series are better engineeredthan DSTJ. Resistance to fatigue should be greater.

HT has no compatibility with API connections.

Tool joints are precision contoured, threaded on ComputerNumerically Control (CNC) machine tools. Manufacturer advertisesthat OD and ID can be changed on request and still match the pipetorsional strength.

It is recommended not to drift away from common product as thisconnection need to be balanced. A surface ratio between shouldersmust be respected. ESSO in Australia experienced a change in IDand encountered problems. SHELL experienced some tool jointwreckage in their Woodside field in Australia due to iron roughneckjaws spacing. In Brent Charlie, break out revealed impossible on HT55: expertise found neither balling nor physical damage andconcluded in a dope problem. Therefore a metal free threadcompound is recommended like Bestolife or Shell Malleus TC2. Thelatest has a higher friction correction factor and better lowtemperature brush-ability. Still SHELL recommends HT as it meetslargely SQAIR requirements (at the exception of the CHARPYvalues in the weld area)

HT connections are commonly used within TOTAL ’s operations. For example, a 5"1/2 HT55 drill string wasused on TOTAL AUSTRAL ’s CN-1, so far Company Extended Reach Well record. In Thailand, 3"1/2 (13.3# and 15.5 #) grade S 135 HT 38 are used to drill horizontal multi-drain. HI TORQUE is available in sizesfrom 2 3/8 to 6 5/8 inches.

TOTAL SIRRI is currently using some 4" HT 40 14# S135 IU drill pipe for extended reach on SIRRI"E" field.The specificity of those HT drill pipes is that their range 3 to reduce time consumed in tripping and price ofmanufacturing. Tool joints have been requested with a 5"1/8 OD (ID=2"11/16; MUT = 21,500 ft.lbs) to allowfishing in 7" casing 26# and in open hole 6"1/8 with an overshot Bowen series 150SH.An inspection has been carried out on the 2300 meters of drill pipe used on rig Barracuda after 265 hours.Five connections were found damaged but due to transportation and lack of thread protectors and notresulting from drilling operations.TOTAL SIRRI has provided rigs with pipe handling equipment such as stabbing guides, special dope, all kinds ofcross over and saver subs for the top drive system.Indeed, some modifications are actually necessary on rig equipment when using HI TORQUE connections.

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They are mainly due to the longer tool joint. For example, bells and elevators need to be adjusted; mudscreen is to be installed in a hanger sub as there is no internal seat on tool joint. Note that it is notrecommended to install mud screen into the saver sub as firstly it is time consuming to check and secondlywash out can result on saver sub itself. Spacing between rams on BOP stack is another feature to adjust toensure tool joints are not located in front of shear rams.

Following is a list of equipment requiring modifications.

½ Adjust spacing on BOP stack to avoid tool joint in front of shear rams½ Order HT connection safety equipment (kelly cock…)½ Install shorter saver sub when using Pipe handler½ Install pressure limiter on iron roughneck to limit pressure on dies½ Locate mud screen in hanger and corrosion coupon in Drill collar (no seat in HT connection)½ Provide longer brush to dope properly shoulders½ Add booster to allow shearing bigger OD drill pipe

In the case of TOTAL SIRRI operations, space out of the string for shut in the well is easier and faster.Among disadvantages experienced it can be noticed the difficulty in finding safety equipment with thisconnection, extra cost in cross over, saver subs, fishing equipment, elevators and slips. Handling range 3drill pipe required to modify mouse hole and revealed extra care was necessary while racking as at hightemperature pipe have tendency to buckling.

At the contrary, 4" HT 40 drill pipes were not recommended in TOTAL INDONESIA as this connection ispretty sophisticated and serviceability over there could not be ensured.

Drill pipes and HTconnections

OD ID Torsional Yieldstrength

Tensile YieldStrength

Make Up Torque

2"3/8 6,6# G105 HT 26 3 3/8 1 ¼ 8,800 313 5,3003"1/2 15,5# S135 HT38 4 ¾ 2 7/16 28,400 708 17,1004" 15,7# S135 HT40 5 ½ 2 9/16 40,000 838 24,0004"1/2 20# S135 HT46 6 ¼ 3 58,700 1,048 35,2005" 19,5# G105 HT50 6 5/8 3 ½ 59,300 1,109 35,6005"1/2 24,7# S135 HT55 7 3 ¾ 87,700 1,448 52,600

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XT, eXtreme Torque is a project still under field test. The idea is to change the taper to get more torqueavailable at the connection DQG to add a metal seal.

GRANT has received order (October 1998) for the first 5"7/8 20# XD150 drillpipes with XT 57 connection from ARCO for a well in China.Tool joint dimensions (7"OD - 4"ID) are similar as for a 5"1/2 HT 55connection and allow fishing operations. 6 turns (versus 4 for HT 55) arenecessary to make up, and torque is applied with 30°’s tong placement.Because of this different taper, transmissible torque is greater at 60,000 ft.lbs(versus 46,300 ft.lbs). It is worth noting that this is a fairly light drill pipe (20ppf) offering a gain of about 30% in pressure losses.NKK had already attempted to introduce a higher grade’s drill pipe(170Kpsi) but experience revealed problems to seat the slips properly andseveral wash out occurred. For GRANT 5"7/8 20# XD150 drill pipes itseems this item has been investigated.Drawbacks to mention are cost about 20% higher and that one inch is lostduring re-cut.No Field test have been carried out yet and only available publication is �3XUSRVH�EXLOW�'ULOO�SLSH�IRU([WHQGHG�5HDFK�GULOOLQJ���63(��������E\�0��/��3$<1(��$5&2�(3�7HFKQRORJ\

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The series 500 Wedge Thread drill pipe tool joint was introduced in 1994 and the first string run in early1995.

Wedge Thread drill pipe tool joint is a tapered, two-step threadedconnection specially designed for high torque, high circulation ratedrilling. It is also convenient for small diameter.

Thread design is similar to a dovetail shape; Wedge Thread is anhyperstatic connection. There is no shoulder contact. The threadflanks provides the positive torque stop. Thread is longer than API’sin order to stand all flexion stress transmitted along the thread flankand thus avoid shearing thread. The limit torque is in theoryequivalent to the shearing of all thread flanks as make up torquedoes not result in any radial, axial or hoop stresses.

The torque strength developed by the flanks of the Wedge Threadeliminates OD or ID restrictive limitations encountered on APIconnection because of stress concentration at last pin thread:• Being independent of the tool joint OD the torque strength rating

of the drill pipe is retained for the life of the tool joint.

• Hydraulic efficiency is improved by allowing a large ID through thetool joint. In terms of hydraulics WT drill pipe tool joint is amongthe best on the market as its wall thickness can be significantlyreduced. Moreover the ID is flush and make pumping downwireline component safer.

• Sealing capability for both internal and external pressure isprovided by the tapered, dovetail Wedge Thread and lubricant.Stress reduction grooves are machined in the root of the largestep of the pin to provide a escape path for excess threadcompound and to reduce high stress levels associated with over-doping.

• A wear indicator is provided by the separation at the box face.The tool joint should be sent for recut when the separationreaches 0.1 mm (0.004"). The bevel provides an indication of ODwear. The tool joint retains rated tension and torque strengthdown to the bevel diameter.

This is a very sophisticated connection that only HYDRIL can repair.Still damaged thread can be field repair to a certain extend.There is obviously no compatibility with any other connection type.

One difference between WT and API tool joints is the increasedrotation of the Wedge Thread from the hand tight to the power tightposition, taking up to ½ revolution.

The Bending Stress Ratio is generally lower than of a comparable number API tool joint.

In the Wedge Thread neither pin nor box use a conventional shoulder. Since the pin and the box will nothave this dissimilar stress range, the API BSR values will not be applicable. HYDRIL recommends BSRbetween 1 and 1.5 for drill collar.

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Special care must be brought when choosing a Wedge Thread connection for drill collar as ID and ODcombination would result in a BSR out of range (BSR values comprises between 1.1 and 3).

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WT is recommended for extended reach wells’ application as they offer the best torque & hydraulicscombined performance. A break out guide is also recommended as the operation might reveal tricky: theguides maintain alignment of pin and box and allow for a straight lift without hanging up. Because thethreads and lubricant are used to create the seal, selection and application of the thread compound warrantindividual attention. Compounds that contain solid fillers are required. Drill pipe tongs with a continuoustorque applicable are also beneficial.WT also finds some application in cases such as 2"3/8 drill pipes with WT23 connection for cleaning out a4"1/2 liner or running TCP guns as clearance between tool joint and liner ID is restricting.TOTAL OIL MARINE runs 2"7/8 10,4# S135 WT23 to clean out 5" liner.

TOTAL AUSTRAL have also experienced Wedge Thread on its challenging extended reach well CN-1:About 180 stands of 4" WT38 S135 (4"3/4 OD and 2"9/16 ID) drill pipes were run to drill the 6"1/8 phaseafter setting the 7" liner from 6259 m to 10025 m. 4" WT 38 makeup torque ranges from 9,000 to 31,500ft.lbs. In CN-1 case torque repartition calculations conducted drilling engineers in choosing a makeuptorque of 20,000 ft.lbs. For this first run the Wedge thread connections have proven their efficiency undersevere drilling conditions as world-wide record of 11,021 m extended reach target has been reached. Butthe most noticeable Wedge Thread related event occurred during geological side track when the drillstringbecame stuck at 10,030 m. To free stuck pipe surface torque was increased up to 45-47,000 ft.lbs andtransmitted down-hole as much as possible with reciprocation. Tripping out indicated that stuck point waslikely within bottom hole assembly as all connections till down-hole motor have been over-torque. Torquerequired to break out was from 35,000 ft.lbs to 55,000 ft.lbs. As torsional yield is given at 41,000 ft.lbs, alldrill pipes were inspected. Separation at the box face reached 3 mm indicating the connection could havesustain additional travel of the pin into the box.Inspection rejected 6 joints only for minor damaged most of which probably occurred while laying down drillpipes.From this experience Wedge Thread capability is confirmed. So is field repair. (We recommend referringdirectly to TOTAL AUSTRAL engineering team in Tierra Del Fuego for more comprehensive feedback, M.Naegel, E. Pradié and R. Vighetto)

Of course in terms of cost this connection is more expensive to buy. HYDRIL merchandises some runningtime comparison and some field repair and re-cut history: they pretend WT tool joint average one end re-cut and two field repairs per rental. More turns are required to makeup the connection so more rig timespent.

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With slim hole technology pipe wall is thin, shoulder on connection narrow and taper low, meaning abetter guidance is required. This is obtained by increasing thread length. Connection tightening is thenmuch longer.

SECURITY DBS offers two types of Slim Hole drill string:

• SH 66 (66 mm/2.6" tool joint OD) for 2"1/4 tube• SH 121 (105 mm OD) replacing SH 111 for 3"1/2 body

They are double shouldered, each shoulder supporting a portion of the axial force due to the makeuptorque. Stored energy within the connection is low. The thread is associated with stress relief groove.Sealing ability is said to be up to 600 bar with fluid.

One major application of SH series is wireline coring.

Both SH types are flush ID. The threads are conical with a conicity of about 1°.

Following are presented mechanical characteristics of drill pipe SH series:

,WHPV 6+��� 6+����OD 2.25" 3.50"• Body ID 1.89" 2.92"OD 2.60" 4.125"• Tool Joint ID 1.80" 2.92"

• Core diameter OD 1.32" 2.02"• Weight 4.3 lb/ft 10.6 lb/ft• Torsion yield point 4,400 lb.ft 12,600 lb.ft• Torsion tensile

strength5,900 lb.ft 21,650 lb.ft

• Traction Yield Point 110,000 lb 289,000 lb• Traction tensile

Strength135,000 lb 329,000 lb

• Makeup torque 2,050 lb.ft 7,200 lb.ft• Maximum Pulling

Force88,800 lb 220,000 lb

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DBS SLIMHOLE is designed for very specific application. They have been used and box weakness wasproven. The BSR is between 1 and 1,4. But it seems they have been used out of purpose above theircapacity in wells with high vibrations. FORASLIM drilled 17"1/2 section with such drill pipes.

No evaluation is proposed for this connection because its range of application is restricted and nothingcomparable to the other high torque tool joint.

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This connection is similar to NKK’s DSTJ. It replaces obsolete previous High Torque with which British Gasexperienced problems.

Connection OD ID Torsional Yieldstrength

Tensile YieldStrength

Make Up Torque(pin or box weak)

TuffTorq NC26 3 3/8 1 ¼ 9,002 313 5,401TuffTorq NC38 5 2 9/16 27,700 649 16,600

1R� 63(�� ,$'&�� $60(� RU� 27&� SDSHUV� KDYH� EHHQ� SUHVHQWHG� WR� GDWH� RQ� 7XII� 7RUT� FRQQHFWLRQV�&RQVHTXHQWO\�WKHUH�LV�QR�UHSRUWHG�H[SHULHQFH�RQ�7XII�7RUT�XVH�LQ�WKH�LQGXVWU\��GHVFULSWLRQ�JLYHQ�EHORZ�LVEDVHG�RQ�WKHRUHWLFDO�DQDO\VLV�RQO\�The OMSCO Tuff Torq connection is interchangeable with the DSTJ connection and will withstand the samemagnitude of torsional and tensile loads before failure. It will also interchange with standard API connections butwill only withstand the torsional and tensile loads that are recommended by the API because there is nosecondary internal shoulder. The primary difference between the Tuff Torq and the DSTJ is in the design of thebox stress relief groove. The Tuff Torq box relief groove does not require more than 3/8inch loss in length duringrecuts but still relieves stress because of the larger radius.

Benefits of the Tuff Torq connection features include the following:

1. Higher torque can be carried by the Tuff Torq than an API connection because of the secondaryshoulder between the pin nose and the box throat. The actual increase in torque is proportional to theaverage radius of the pin nose and the thickness of the shoulder. The minimum makeup and yieldtorque are calculated using modified API equations that were developed in Jack Smiths SPE paper no.35035 “Box OD Stability of Double Shoulder Tool Joints at Catastrophic Failure.” These wereconfirmed by full scale testing of “Tuff Torq tool joints.

2. The tension characteristics remain the same as API since the feature that carries tensile loads is thepin thickness at 5/8” distance from the external shoulder. Torque – Tensile plots show that highertorque can be sustained at the same tensile loads when compared to API connections.

3. Tuff Torq can sustain more wear on the tool joint outside diameter than API tool joints beforeappreciable loss of torque because the internal shoulder holds a substantial portion of the torque loadand is not affected by external wear.

4. Mud pressure losses may be lower using Tuff Torq connections than for API connections. Larger pinand box inside diameters will still allow higher torque because of the internal shoulder. However thereare practical limits to the maximum pin bore sizes before the internal shoulder becomes ineffective asa torque carrying feature and there is a drop in tensile strength.

5. The rate at which Tuff Torq drill pipe is run into and out of the hole is the same as for regular APIconnection pipe. Since its thread is the same and the threaded length is the same, it requires the samenumber of turns as API to make or break. Care must be taken not to damage the pin nose shoulder butno more precaution is required than for API pipe.

6. Repairs of the threads and shoulders are at the same rate as for API threads. Both the outershoulders and the threads wear at the same rate as for API since they are API. The internal shoulderdoes not appear to wear any faster than the outer shoulder as long as the torque has not exceeded theyield strength. If it has, then the connection will have to be recut just as would be regular API threads.About 7/16” is lost with each recut to accommodate the modified stress relief groove in the box.

7. Refacing cannot be performed on the threads since the outer and internal shoulders must remainwithin 0.005 inches of their nominal distance to perform correctly. If the external shoulders contactbefore the internal shoulders are within 0.005 inches of each other, then the interval shoulders will nottake their required torque before the external shoulders begin to deform under maximum load. If theinternal shoulders meet first, then there may not be a good hydraulic seal and a washout may result.

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Tuff Torq connections are applicable for both oil and gas wells where high torque is a problem. Thisincludes extended reach, horizontal and deep vertical wells. On HT/HP wells the higher temperaturewillreduce the yield strength of the tool joint material and will reduce the maximum connection torqueby the same proportion.

9 Under normal rig operating conditions, there is no required time span to store sufficient energy in theconnection. Once the primary and secondary shoulders have made contact, less turn is required tomake up to the required torque than for API connections. This may be due to preventing pin elongationwith the secondary shoulder.

10 Stress relief grooves can be cut on pin connections but since there is an internal shoulder on the boxhere, it is not possible to cut either a bore back or a box stress relief groove in the Tuff Torq box. TuffTorq have not been requested on Heavy Weight drill pipe or drill collars as since they are run at thebottom of the hole and are normally not subjected to as much torque as the drill pipe.

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Each connection type studied has been evaluated according to already above mentioned criteria :

• As current standard for the industry, API connection remains satisfactory for conventional drillingoperations. It is cost effective in a way that it is the cheapest on the market and it allow a goodmaintenance. For most complex drilling its torque capacity and hydraulics characteristics are penalisingand it simply cannot be used. “Stress balancing” is limited and does not eliminate hydraulics problems.

• DBS SH series connection has a limited field of application: slim hole. So it has not been evaluated inthe table to avoid confusion.

• OMSCO Tuff Torque is not so popular within the industry and QR�SXEOLFDWLRQV�RU�SUHYLRXVO\�UHSRUWHGH[SHULHQFH�LV�DYDLODEOH. This connection has not been included in the comparison.

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API ♥ ♥ ♥♥♥♥ ♥ ♥♥♥♥ ♥♥♥♥ N/ANKK – DSTJ ♥♥ ♥♥♥ ♥♥♥ ♥♥♥ ♥♥♥ ♥♥♥ ♥♥♥♥GRANT - HT ♥♥♥ ♥♥♥ ♥♥ ♥♥♥ ♥♥♥ ♥♥ -HYDRIL - WT ♥♥♥♥ ♥♥♥♥ ♥ ♥♥♥♥ ♥♥ ♥ -

Hearts (♥) are used to define the level of satisfaction and confidence.

• NKK DSTJ offers an interesting compromise despite torque benefits is not tremendous when comparedto API standard connection. Hydraulics characteristics are good. But its great advantage is its APIinterchangeability: No need for crossovers thus saving and time and money. NKK allows re-facing of thepin end once only which is the main burden. )RU�WKHVH�UHDVRQV�1..�'67-�LV�UHFRPPHQGHG�

• GRANT PRIDECO HT series provides better torque characteristics than NKK. Special equipment andrig modifications are required meaning extra cost involved. However as the tool joint is longer than NKKmore than one re-cut is allowed. 727$/�H[SHULHQFHV�KDYH�SURYHQ�VDWLVIDFWRU\.

In NKK DSTJ and GRANT PRIDECO HT-series pin face acts as a sealing area. It is strongly recommendedto use pin end protectors when raking up in the mast or laying down drill pipes.

• HYDRIL Wedge Thread connection, due to its higher cost, should be limited when both hydraulics andtorque can not be satisfied by other connection type. This later presents the best engineering designthat brings confidence for the most challenging wells. As this technology will spread over contractorsand operators its servicing should be enhanced. It also finds some application in cases such as 2"3/8drill pipes WT23 for cleaning out a 4"1/2 liner or running TCP guns as clearance between tool joint andliner ID is restricting. +<'5,/�:HGJH�7KUHDG�FRQQHFWLRQ�LV�GRXEWOHVV�UHFRPPHQGHG�LQ�FRPSOH[DQG�FKDOOHQJLQJ�ZHOOV�

As mentioned above for HYDRIL Wedge Thread connection, the pin needs guidance when breaking outuntil it completely releases from the box. WEATHERFORD has specially developed break out guideswhich maintain alignment of pin and box and allow a straight lift without hanging up. Drill pipe tongs with acontinuous torque applicable are also beneficial.

A general recommendation is to always check dope friction factor and compatibility with selectedconnection. Metal free dope is recommended.

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������������*����SLSH ����� ��� �IW�OEV�NC 26 3 3/8 1 ¼ 6,875 313 4,125 (b)HT 26 3 3/8 1 ¼ 8,800 313 5,300WT 26 3 3/8 1 ¼ 12,300 416 2,800 – 9,800������������*����SLSH ������ ���

NC31 4 1/8 2 13,200 495 7,920 (p)HT31 4 1/8 2 16,300 485 9,800WT31 4 1/8 2 28,500 697 6,100 – 22,500�����������*����SLSH ������ ���

NC31 4 1/8 2 13,200 495 7,100NC38 5 2 7/16 22,210 708 13,330HT38 4 ¾ 2 11/16 25,300 587 15,200WT38 4 ¾ 2 9/16 41,000 877 9,000 – 31,500������������6����SLSH ������ ���

NC38 4 ¾ 2 9/16 19,170 649 11,500 (p)HT38 4 ¾ 2 7/16 28,400 708 17,100DSTJ NC 38 4 3/4 2 9/16 23,630 649 14,200WT38 4 ¾ 2 ½ 37,950 907 9,000 – 31,500

���������6����SLSH ������ ���NC 40 5 ½ 2 36,400 1,080 18,900HT40 5 ½ 2 9/16 40,000 838 24,000WT 40 5 1/2 3 1/8 54,000 998 12,000 – 42,000

����������6����SLSH ������ ���NC46 6 1/4 2 ¼ 53,940 1,307 33,360 (p)HT46 6 ¼ 3 58,700 1,048 35,200DSTJ NC46 6 ¼ 3 49,530 1,048 29,700DSTJ NC46 6 ¼ 2 ¼ 68,570 1,419 41,100WT46 6 1/4 3 1/2 70,000 1,280 15,000 – 56,000

���������*����SLSH ������ �������NC50 6 5/8 3 ¼ 51,710 1,269 31,025 (p)HT50 6 5/8 3 ½ 59,300 1,109 35,600DSTJ NC50 6 5/8 3 ½ 56,560 1,109 33,900 (p)DSTJ NC50 6 5/8 3 ¼ 65,650 1,268 39,400 (p)WT50 6 5/8 3 5/8 1,090,000 1,444 23,000 – 86,000

���������*����SLSH ������ ���NC50 6 5/8 2 ¾ 63,410 1,552 38,040 (p)HT50 6 5/8 3 ¼ 71,000 1,269 42,600DSTJ NC50 6 5/8 2 ¾ 81,620 1,552 49,000 (p)DSTJ NC50 6 5/8 3 ¼ 65,650 1,269 39,400 (p)WT50 6 5/8 3 5/8 1,090,000 1,710 23,000 – 86,000

������������*��� ������ ���5"1/2 FH 7 ¼ 3 ½ 72,480 1,619 43,490 (p)HT55 7 4 77,200 1,265 46,300DSTJ 5"1/2 FH 7 ¼ 3 ½ 81,430 1,619 48,900(b)DSTJ 5"1/2 FH 7 4 69,140 1,265 41,500 (p)

������������6��� ������� ���5"1/2 FH 7 ½ 3 87,170 1,926 52,300 (p)HT55 7 3 ¾ 87,700 1,448 52,600DSTJ 5"1/2 FH 7 3 ¾ 79,200 1,448 47,500 (b)WT54 7 4 3/8 120,000 1,404 25,000 – 90,000

������������*��� ������ ���6"5/8 FH 8 ¼ 4 ¾ 86,240 1,678 51,740(p)HT65 8 5 99,800 1,448 59,900WT56 7 4 5/8 131,000 1,473 27,000 – 99,000

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$PHULFDQ�3HWUROHXP�,QVWLWXWH�"Recommended Practice for Drill Stem Design and Operating limits, API RP 7G", 15th edition, January 95

6HFXULW\�'%6�"Slimhole drillstring, reference PFBR711.WPS, dec 95"

206&2�,1'8675,(6�"OMSCO’s Major Products catalog, july 97"

*5$17�35,'(&2��'ULOO�SLSH�6HPLQDU���+�6(5,(670��+,�7RUTXH�DQG�H;WUHPH�7RUTXH�&RQQHFWRUV��5RWDU\�6KRXOGHU�+DQGERRN���+�VHULHV�GULOO�SLSH�FDWDORJ������&'�520�������+RZ�WR�UHGXFH�GULOOVWULQJ�IDWLJXH�IDLOXUHV�LQ�D�FRUURVLYH�HQYLURQPHQW�� by Gerald Wilson, Worldoil, oct 98�5HSODFLQJ���,QFK�DQG�������,QFK�'ULOO�3LSH�ZLWK�D�VLQJOH�VWULQJ�RI���LQFK�GULOO�SLSH� S. Mehra, sedco Forex & J.E.Smith, Grant Prideco, SPE/IADC 37648

1..�(8523(�/7'��7RUTXH�UHVLVWDQFH�RI�WXEXODU�FRQQHFWLRQV�XQGHU�VLPXODWHG�ZHOO�FRQGLWLRQV� by E. Tsuru, M. Oka & K. Maruyama,Yawata R&D laboratory, PD vol. 65, 607 848, Drilling Technology ASME 1995�0DNH�XS�WHVW�UHVXOW�DQG�ILQLWH�HOHPHQW�DQDO\VLV�RI�'67-�WRRO�MRLQW�� NKK Technical bulletin, Sept. 95

+<'5,/�±�:($7+(5)25'�6HULHV������:HGJH�7KUHDG���'ULOO�3LSH�7RRO�-RLQW�� HYDRIL Bulletin 9402-C�:HGJH�7KUHDG���ILHOG�+DQGERRN�� second edition�5HGXFH�7RUTXH��'UDJ�DQG�:HDU�±�0DWHULDO�VHOHFWLRQ�IRU�FHQWUDOL]HUV�XVHG�LQ�KLJKO\�LQFOLQHG�DQG�KRUL]RQWDO�ZHOOV��by H. Kinzel, EVI Weatherford oil Tool GmbH Germany, R.L. Colvard, EVI Weatherford UK Ltd, SPE/IADC47804, Jakarta 7-9 Sept. 98

7�+��+,//�$662&,$7(6��6WDQGDUG�'6������'ULOO�6WHP�'HVLJQ�DQG�,QVSHFWLRQ�� second edition, March 98�'6������'ULOO�6WULQJ�'HVLJQ��)DLOXUH�3UHYHQWLRQ�� 1998

727$/�(;3/25$7,21�352'8&7,21�9DOLGDWLRQ�RI�DGYDQFH�K\GUDXOLF�PRGHOOLQJ�XVLQJ�3:'�GDWD�� Ph. Charlez, TOM, at OTC 8804���,QFK�'ULOO�3LSH�UHTXLUHPHQWV�� M. Campos, TOTAL SIRRI-DUBAI, April 97"�([WHQGHG�UHDFK�'ULOOLQJ��&KDSWHU����GULOOVWULQJ�GHVLJQ�� S. Handcock, EAP & T. Delahaye, TEP, June 95

27+(56�([WHQGHG�5HDFK�'ULOOLQJ�±�:KDW�LV�WKH�OLPLW"�� C.J. Mason, BP Explo. Operating Co. Ltd and A. Judzis, BP(Alaska), SPE 48943�'ULOO�SLSH�0DQDJHPHQW�H[WHQGV�GULOOVWULQJ�OLIH�� Jeff shapard, Global Marine Drilling Co. Oil & Gas Journal,Oct 28, 1991�3XUSRVH�EXLOW�'ULOO�SLSH�IRU�([WHQGHG�5HDFK�GULOOLQJ�� SPE 39319, by M.L. PAYNE, ARCO E&P Technology³,QWHJUDWHG�0HWKRGRORJ\�IRU�(5'�5LJ�6L]LQJ�DQG�:HOO�3ODQQLQJ´� SPE/IADC 52837, by M.L. PAYNE, ARCO E&PTechnology

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OMSCO INDUSTRIES LtdArthur Reilly, engineering supervisor,Dunnswood Rd, Wardpark south, Cumbernauld,Glasgow G67 3ETTel. : + 44 (01236)618713Fax : + 44 (01236) 727763

GRANT PRIDECOFrançois Kessler,1274 rue du HouecF-40180 CandresseTel.: 05 58 90 86 28Fax : 05 58 90 86 27Francois.kessler@wanadoo.fr

NKK EUROPE LTD,Kazuo Yamazaki, senoir technical manager, steel division4th floor west block11 Moorfields HighwalkLondon EC2Y 9DETel.: + 44 (0171) 628 2161Fax : + 44 (0171) 638 1374kaz-yama@jais.co.uk

HYDRIL S.A;Nis Krug, consultant, Marketing & SalesRoute de Beaumont 20, P.O. Box 163CH-1709 Fribourg, SwitzerlandTel.: + 41 (26) 422 1251Fax : + 41 (26) 424 9165Home : +34 72 660 834 (Spain)

SECURITY DBSJean valery Garcia, Product engineer DHTS74, Avenue du Pont de LuttreB-1190 BrusselsTel. : +32 2 348 3231Fax : +32 2 348 3584jgarcia@Securitydbs.com

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• Tool joint & Tube ODWear

• Excessive tolerancesspecially in wallthickness deviations(12.5%)

• Slips dies can make deep& sharp notches thatform cracks

• Never « shotgun »connections with kellyspinner

• Internal corrosion • Unspecified control of thelength and shape of theinternal upset (Miu)

• Maintenance of slips, dies& bushing

• Check torque gaugeaccuracy

• Fatigue cracking in the slipand internal upset area

• Ability of tool joint thread& shoulder design towithstand stress.

• Use two tongs to avoidbending pipe & ensurecorrect placement

• Individual marking permitstracking downhole wear

• Physical damage to thetool joint threads &shoulders,and to thetube

• Number of manufacturer,variance in mill andprocessor capabilities(wall thickness –5/6%and upset formation)

• In case of missed stabpick up the pipe toprevent scoring theshoulder faces andcause a faulse torquereading

• Well-planned stand rotationavoid stressing string atthe same part Rotatebreaks in stand preventsovertorquing unbrokenconnections

• A dope stand avertscontamination andmake it easier to applythread compounds

• Clean carefully threads anduse zinc-based or leadbased compound.

• Supply thread protectors

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• Internal plastic coating can helpcombat corrosion

• H2S embrittlement form under high pressurewithin the steel grain structure

• Maintain hole curvaturesbelow 2.5°/100 ft

• Use oil-based mud wheneverpossible

• CO2 combined with water form carbonicacid,immediately reacting with exposediron surfaces causing severe pitting,

• Replace worn drill collarsthat may have low BSR

• Use smooth and long upset taper • Failure occur at the most stressed areas,such asthe last engaged thread of the pin

• Check for proper torque onall connections

• Inject oxygen scavengingchemicals into the mud suctionlines

• In case of water-based mud maintain a highmud pH (10.5 min)

• Minimize backreaming andstring rotation offbottom

• Use motor wheneverpossible

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The following table summarises FPL recommended practices for drill pipe design in terms of stiffnessratio (SR). This Stiffness Ratio applies to any section change within the drill string.This is a completely different notion from Bending Stress Ratio (BSR) which applies to avoid fatiguedamage resulting from an unbalanced connection.Experience defines a non-scientific “wild guess” or rule of thumb: VHFWLRQ�FKDQJH�PXVW�EH�NHSW�EHORZD�6WLIIQHVV�5DWLR�RI�����IRU�QRUPDO�GULOOLQJ�FRQGLWLRQ�DQG�EHORZ�����XQGHU�VHYHUH�FRQGLWLRQV�

Components Allowed Components toconnect above

Stiffness Ratio (SR)

DC 11” x 3” DC 9”1/2 x 3”DC 8” ½ x 2” 13/16DC 7” 1/4 x 2” 13/16DC 6” 1/2 x 2” 13/16

SR = 1.6SR = 2.2SR = 3.5SR = 5

DC 9”1/2 x 3” DC 8” ½ x 2” 13/16DC 7” 1/4 x 2” 13/16DC 6” 1/2 x 2” 13/16

SR = 1.4SR = 2.3SR = 3.2

DC 8”1/4 x 2” 13/16 DC 7” 1/4 x 2” 13/16DC 6” 1/2 x 2” 13/16HWDP 5” – 50 lb/ft

SR = 1.5SR =2.1SR = 5.1

DC 8” x 2” 13/16 DC 7” 1/4 x 2” 13/16DC 6” 1/2 x 2” 13/16HWDP 5” – 50 lb/ft

SR = 1.4SR = 1.9SR = 4.6

DC 7” 1/4 x 2” 13/16 DC 6” 1/2 x 2” 13/16HWDP 5” – 50 lb/ft

SR = 1.4SR = 3.4

DC 6” 1/2 x 2” 13/16 HWDP 5” – 50 lb/ftDP 5” – 19.50 lb/ft

SR = 2.4SR = 4.6

HWDP 5” – 50 lb/ft DP 5” – 19.50 lb/ft SR = 1.9DC4” ¾ x 2” 1/4 DP 3”1/2 – 13.30 lb/ft SR = 3.8

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REDUCETORQUE/DRAG

LIMITED BYDRILL PIPE

DESIGN

LIMITED BYTOP DRIVE or

ROTARY

TORQUELIMITATION

TRAJECTORY DESIGNOPTIMIZATION

- PSEUDO CATENARY

BHA DESIGN- STABS- REDUCE DC- REDUCE HWDP

BIT SELECTIONTRICONE vs PDC

CASED HOLETORQUE REDUCTION

TOOLS

MUD ADDITIVES- LUBRICANTS- BEADS

MUD SELECTION- OBM vs WBM

OPEN HOLETORQUE REDUCTION

TOOLS

UPGRADETOP DRIVE orCHANGE RIGSELECTION

ENSURE MAXIMUMTORQUE POWERIS AVAILABLE

UPDATE EXISTINGDRILL PIPE

HIGH FRICTIONTHREAD COMPOUND

INCREASE MUT BYSTRESS BALANCING

DESIGN NEWDRILL PIPE

LARGER SIZE5”1/2, 5”7/8, 6”5/8

HIGH TORQUETOOL JOINTS

HIGHER GRADE

PURPOSE BUILTERD DRILL PIPE

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LOWERTHE PRESSURE AT

GIVEN RATES

LIMITED BYPRESSURE

LIMITED BYPOWER

HYDRAULICLIMITATION

ENLARGE SURFACEPIPING

LOWERMUD RHEOLOGY

MODIFY DRILL PIPESTRATEGY FROM 5” DP

BASE PLAN :• COMBO

- 5”1/2 x 5”- 5”7/8 x 5”- 6”5/8 x 5”

• FULL- 5”1/2- 5”7/8- 6”5/8

• OTHER COMBO- 6”5/8 x 5”1/2- etc

CASED HOLETORQUE REDUCTION

TOOLS

MODIFY BHA DESIGN :MWD/LWD ∆PPDM ∆P,VGS ∆PID CONSTRAINTS

MODIFY BIT SELECTION-INCREASE TFA

ADD INTEGRATEDPOWER

ALTERNATIVESOURCE FOR

“HOTEL” LOADS

RISK ASSESSMENTFOR EXTENT OF HOLE

SELECTION TO BEPOWER LIMITED

MODIFY PUMPSTRATEGY TO USESMALLER LINERSAT HIGH RATES

IMPROVE POWERFACTORS WITHAUTOMATEDCONTROLS

ADD AUXILLARYPOWER

UPGRADE PUMPFLUID END

FORENTIRE PUMP

&HP PIPING

LOWER THEREQUIRED RATE TO

CLEAN HOLE

UPGRADE FORPRESSURE

SYSTEMATICAPPLICATION OF HOLE

CLEANING ASSISTS :- SHORT TRIP- BACKREAM- PILLS

OPTIMIZE MUDRHEOLOGY AND WEIGHT

TUNE RATEREQUIREMENTS WITHHOLE CLEANING PWD

ANALYSIS

CONTROL DRILL HOLESECTION INTERVAL ATISSUE

MECANICAL HOLECLEANING AIDS

LIKE ENHANCED DP

MAXIMIZE DRILLINGROTATION :

- HIGH RPM- BHA DESIGN- WALK COMPENSATION- VGS / HVGS- RSS