Design of Drill Pipe

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the design of the drillpipe for use in oil well drilling operation


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    The Design and Performance Characteristics ofAluminum Drill Pipe





    This paper outlines the approach atz~ solutions to theproblems associated with - the design and deve!optnent ofaluminum as a drill stem. for rotary drilling. A current

    field history on tdumitsutn as a drilling tool is includedto assist the reader in judging the selection of engi-neering compromises [n the light of present field perform-ance and to acquaint the reader with. the present status ofaluminum dril! stetn in the drilling art.

    Following proof of satisfactory operation of the firstcduminum drill string; 25, more strings (ske TabIe 1] have

    ~gone into. worldwide operational ttse. A study ,of theirperformance indicates: (1) no operational disadvantages,

    (2) compatibility wfth. present drilling muds, (3J mlxed-



    transfer of stresses and a satisfacto~y fatigue life. Thisand other design and performanc~ considerations are dealtwith in this report.

    After the development of a satisfactory aluminum drillpipe it was necessary to demonstrate the eeonomic ad-vantage of this tool, This too has been accomplished anddata are available to show the competitive position ofaluminum drill pipe.

    Acceptance of ahsminum drill pipe is attested to bydemonstrated success i and by re-orders by present users:Five users have purchased their second strings of alum-inum drilI pipe. One user has purchased his fourth string.

    Statement of Theory




    . .

    string operat(onir are successful, (4) hand and power slipsare operational{ (5) .no failures in the tool-joint area, (6)tioproblems it? fishing or other special USCS,(7) normalwear on. pipe body comparable to steel and (8) less thant~rmal wear on tool jo[nts.

    These facts about the. present operational status ofalutnin?tni drill pipe de-mcmstrate that successful drillingtools can be designed and constructed of aluminum. Fieldand laboratory studies are continuing in order to improveand expand the u,veof aluminum jor.drill pipe.


    Introduction , .

    To make functional drill pipe from aluminum requiredmore than a casual selectior, of engineering compromises.The target was a d@ling tool that would substantiallymeet the physical characteristics of Grade E steel drillpipe but, if possible, also incorporate the many desirablecharacteristics found in low-allov steel drill Ltiue(Grade D)such as toughness, concentric w%ar,and, lowembrittlementrate.

    If aluminum could be successfully fabricated into de-pendable dr~ll stem, the advantages of this light materialshould reduce drilling costs. A few of the readily apparentareas of improved economy are: (1) rig investment, (2)transportation, (3) wireline life, (4) hoisting fuel savingsand ~(s) hoisting time reduction.

    On the theory that aluminum drill pipe would lowerdr~lling costs, a project was initiated about 14 years ago,


    length mn~cw:(ftl WNe% L%h locatlm,

    41/..1. F+t)-







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    15 9,89023 4,62016 6,350

    6,563!4 9,550 8 8,500

    4,5001! 4,650

    ~1/2 1 S,po.

    from: Texas. Cal If,Okla.ChileN.E, TexasN.Z. TexasAlberta, CanadaAlberta, CamdaN.E. Texas, Calif.

    It was recognized early in the aluminum drill pipe pro-,. -.,W11. 11,620 77,000 9 8,55072,

    N .E , Texas12,000

    gram that aluminum alloys could not be beat utilized in a ,, IS. ,~~::,61,634 5 12,300, La., Miss.39,013 3,900 Ok&OmO

    dbsign that copied the then available steel driil pipe. It14. 11;355 ,! 1T ,:5515, S:olo 15,000 Mont.

    1;:*was necessary to balance the design, alloy choice, spength, 16, 4,020 9,f7017,


    corrosion and, wear resistance of aluminum alloys into a.* *.


    7,020 4,55s 1 Colo.19. 4,740 57,351 7,:90

    workable tool, one. ctspable of sustainigg_the; spe$ses ~f, ~ ~o.. _._u,s~o. ~.-z#.l.?.o._ -1&l,: 10,OSO..._. N$, .roxm .,. -.N. Okla.rotary diiilhi-gr - -- PiOe

    The application of steei tool jaints to aluminum pipe ,21, 11?5z0 113,427 19 5,950 MIs.:, posed many problems in ofder to achieve a satisfactory, ,, 2Z !J1~.1. pipe

    7,020 20:,:S7; ~33 6,100 La., Miss., Tex.23:.

    OrfginsS manuscript received fn Soelety of Petroleum Engineers oflh?e7,500 * *

    24. 6,000SWdlArabia

    5:800 Aug. S,. 1963. Revieed manuscript received Oct. 80, 106S. Paper me. 1$:;$ .* ,,-~ :


    sented at SPE FsL1 Meting held h New Orleans, Ott, 6.9, 196$. & ,l

    Cqllf..*, Uhzh

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    which has today progressed to a point of full-scale magnL-tude throughout the world,

    Acturil field operation (25 strings) ot ahvninum drillpipe has brought to light other advantages and savingswhich were not apparent at the outset: 2 (1) pipe main-tenance and life, (2) drilling fuel, (3) tool joint life, (4)pumping fuel, (.5) safety and (6) less flow resistance inannuhts.

    Description of Test Eqsdpmetit

    Fsstigue TestA rotating, cantilever betun-type fatigue test tnachinc

    is maintained in the Reynolds Richmond, Vs., labora-tories for full-scale fatigue testing of drill p~pe and drillpipe-tool joint assemblies. The machine has a drive

    mechanism in the head which provides a controlled con-tinuous rotation.

    A deflecting mechanism is located approximately 7 ft,from the head and is equipped with rollers to provide ro-tating support of the test section. The machine is capableof subjecting a test specimen to a bending moment of200,000 in.-lb during a typical test. Fig. 1 shows a schem-atic of the test machine.Tension and Torsion Test

    A, combirai?ion, tension and. torsion testing machine ismaintained at the Reynolds Extrusion Milt in Phoenix,Ariz., for testing full-scale specimens of various shapes,.including drill pipe with tool joints. The machine is sxtp-able of a 750,000-lb tensiIe pull, and the heads can berotated 3600 in either direction. Fig. 2 shows a sketch of.the arrangement,.

    Application of Test E&ipm*

    Fntigue Testing -

    Sufficirmt background has been developed in the fatiguetesting of hand-applied tool joints on steel pipe to providegood fatigue life pnrameters. Most of the tests on the 41.4in, steel drill pipe were run at 300 rpm under a bending

    lRefevences given 21L end of p,auer.





    II I


    F-ig. lDrill pipe assembly fatigue testmachine.





    .-. .


    Fig. ZDrill pipe assemldy tension imd torsion testing.

    l , *


    moment of 1S0,000 in.-lb to produce a bending stress ofabout 35,000 psi at the base of the upset, The deflection of41/2-in, stee] pipe with a lever arm length of 80-in. iS about7/s -in. which is maintained during rotation. Exprience withGrade E drill pipe and hand-applied tool joints indicatean average fatigue life of 400,000 to 600,000 turns orcycles.

    Today, aluminum drill pipe specimens give long con-sistent runs in the million cycle range with. test specimensselected at random from production. Breaks usually OC-cur 4 to 36 in. from the tool joint, which indicate maxi-mum efficiency of the tool joint-drill pipe assembly.

    The tests on 41X-in, aluminum pipe are also run at300 rpm under a bending moment of 150,000 in.-lb whichproduces a bending stress of about 16,000 ,Psi at the endof ihc tool joint shoulder. The deflection of the 41A-in.aluminum is double that of steel or about 13A in. for a Ieverarm length of 80 in, and a 150,000 in.-lb moment. Thispoints up the fact that the aluminum drill pipe can de-flect about twice as much as steel driIl pipe and still be

    , within safe stress limits, ,,,

    Tension and Torsion Test

    The background ,dftensile t&thtg on 4~z in. Grade Epipe indicates an average value of 450,000 to 500,000lb. Aluminum drill pipe shows an average tensiie strengthof 488,000 lb, ranging from 473,000 to 503,000 lb ineight joints selected at random from production prior torelease of the first string. Tests were made which putthe, tension load through the tool joint assembly. FuII.length joints were u~ed (30 ft). No failures occurred in ornear the. tool. joint area. The break areas ranged from4 1/3 to 9 ft from the end of the joint. The test wasmade by gripping the ,outside of the tool joints. The tensileload did not pass through the working, connections of thejoints.) Very limited torsion test data on steel drill pipe wereavailable for comparison.

    A field specimen with a service history of 148,000 ftof hole was given an initial tensile pull of 150,000 lbafter which one emi was rotated 180 clockwise with re-spect to the opposite end. N.o failure occurred. The torquewas then backed off to 120 displacement and the tensiontest continued to a tlnai pLdi of 365,000 lb, at whichpoint a typical tension break occurred in the body, of thepipe. These tests dramatically illustrate the tough tension .and torsion properties of aluminum drill stem, in the Par-ticular design, and its ability to accept abuse.

    Design ObjectivesInitial design objectives for alumisium drill stem con-

    templated physical characteristics comparable to GrtRie Edrill pipe. The design should be compatible With presentrig practices, drilling methods, fishing operations, drillingfluids and all other well drilling operatiofis.Phase One -


    1, To prevent compounding the problems associated .with the irstroduotion, of a new product, a decision was ~made to provide steel tool joints wit