CA2237432A1 - Composite material structures having reduced signal attenuation - Google Patents

Abstract

The present invention relates to composite material structures having reduced signal attenuation properties. In particular, the invention relates to composite drill string components with electromagnetic properties and acoustic properties that enable the use of electromagnetic, acoustic and nuclear sensing equipment to obtain data from a wellbore from within a drill pipe. In a specific embodiment, a composite tube is incorporated with end-fittings which enable its incorporation into a drill string thereby permitting the use of logging equipment from within the composite tube.

Description

COMPOSITE MATE~AL STRUCTURES HAVING REDUCED SIGNAL
ATTENUATION

RELA~ED APPLICATIONS
This application is a co..~ n-in-part of United States Patent Application 08/5~7,337 S filed December 5, 1995.

FIELD OF THE INVENTION
The present invention relates to cul~o~ilt; m~t~r~ Llù~;~ul~s having reduced signal l ion properties. In particular, the inventlon relates to composite drillstring components which exhibit a degree of l~ J~ Y which permits for the tr~n.~itic n of 10 electr )m:~gnPtic fields, acoustic signals and echos and nuclear media thus enabling the use of electrl m~gn~tiç, acoustic and nuclear sensing e~l..;l....~..~ to obtain data from a wellbore from within a drill pipe. In a specific embodiment, a cvlll~o~i~e tube is hlcul~,olaLed with end-fittings which enable its incorporation into a drillstring thereby ~ liLlhlg the use of logging e.l, ;l~ l from within the c~lly-o~iLe tube.

In the process of excava~ g a borehole, it is uull~,llLly the practice to acquire hlr~,.lllaLion conr~rning the formation through the use of m~th~ldologies known as ..lea,,ul~,ll.cllL while drilling (MWD), logging while drilling (LWD), logging while tripping (LWT), and Ill~abul-,.llent while tripping (MWT). These m~th~dologies use sensing technologies and 20 devices such as spectral gamma ray, neutron emission and detection, radio frequency tools, nuclear m~n-otjc. resnn~nre, acoustic imagery, acoustic density, acoustic calipers, gamma ray emi~sion and detection, density logs, sonic logs and a range of other instrum~nt~ti( n to obtain detailed hlrc,llllalion co~ . .li..g the form~til-n :,ullvull.lillg a borehole. These lll~,aSUlCllltlll. technologies require sophi~tir~ted devices or pl.)cedul~ to obtain high quality 25 data about a form~tinn, the level of sophi~tir~tion a direct result of the severity of the downhole operating ellvhol~llle~. Furthermore, this measurement e~ may be design~d to form a component of the drilling e~lui~llellL which requires furt_ersophi~tic~tion in the i"le~,;.;ion of the ~llca~ul~,lllcllL e~ui~llltnL within the drilling C.~ l However, the lllalliage of llle~ul~lllcl~ e~..;l.."~ with standard drilling 30 e.~ is limited in both the quality and type of data which can be obtained from a borehole.

For example, where a logging or ll.ea~u~ tool is used within a drillstring, the type of data and the resolution of that data is limited by the m~tQri~1 properties of the drill pipes of the drill string. In normal practice, drill pipes are steel and, accc,ldi.-gly, limit the ability of logging or ll~a;,~ lllclll tools to acquire a broad range of hlr(~l~l-alion. In particular, 5 ele.;L.u,..~g..P~ir, and acoustic sensing devices cannot be operated from within a metal drill pipe in view of the inability of an cle~ L~ gnPtic or acoustic sensing device to operate through a metal drill pipe. Secondly, the use of sensing devices operable through a metal pipe may result in severe ~ttf nn~tion of any data signal, thereby limiting the accuracy of ul~ li--g a data log of the Çu~ aLion.

10 Once a borehole has been fully excavated, Oy.,lalol~ often contin-1f to acquire formation data from the borehole over the life of its production. In order to ...~ stability in the borehole, it is often l~cç~ I y for the borehole to be lined with a casing, normally a metal casing c~ d into place. Again, the use of metal may prevent or severely aftrn11~tç the operation of sensing ~l";l"" "

I~ Accordingly, there has been a need for tubing for use in both the drilling and casing phases of a borehole which does not prevent or severely ~tten11~te the use of sensing e.l,.;l...-f .-~within the borehole. Thus, there has been a need for tubing that enables the use of a full range MWD, LWD, LWT and MWT technologies.

The drilling/borehole c.~vi-ull---ent is an eA~ llely a~lasive, high stress e..~hu--,.-t;..L that 20 requires very high sl~ldd,ds of p~lrull~allce and quality in drilling e~ These standards and p~lr~ -rc ~ ;rc for drilling e~ ..l are set forth, in part, by the .Amerir~n Petroleum Tn~tih1t~ (API S~e~ n 7 for Rotary Drill Stem P.lPm~ntc) and detail llulll~,luus ~e~-;r~ ;ons for drill pipes and casings (API Sperif r~tinn S for casings~
for use in boreholes.

25 Thus, there has been a need for tubing which meets API specifir~tionc for tlrill~tring CO~ O~ S which further provide the ~-~c~ss,.. y con~lnrtivity to the u~"dLillg freql~en~ies of sensing e-~ used in MWD, LWD, LWT and MWT operations. Specifically, there has been a need for c->n~rosite tubing con~i11ctive to radio frequency and acoustic signals which also result in a re~ rfff n of ~ I ;on of natural decay waves/particles (gamma 30 rays, beta particles, etc.) passing through the tubing.

It is, however, impractical for a composite tube to replace a steel drill string. Acco.~ sly, in that the use of MWD, LWD, LWT, and MWT h~ll.~ tioll requires only a relatively small window to obtain downhole data, only a collG~oll~lillg short section of colll~?osiLe tubing is required to provide the window. Thus, the incorporation of a l~,la~ ,ly short section of composite tubing within a drill string requires metal/composite jlmrtiQn~ with pGlrullnal~ce l~h~r~ct~ri~ti~s equal to those of the cully~G~ile and metal sections of the 5 ~lrill~trin~ which thereby enable the composite tubing to be ~tt~rhPd to metal co llyo~ of the drillstring in a cûllvt;"lional manner. Acu,,lyo~ile drill collar will also act ac a rotary torque absoll,el l~,du~ing the risk of twist-offs as a result of rotary torque build-up in the 11rill.ctring.

As in~ t~Cl above, the downhole drilling envhulllllGllL is severe in terms of abrasion, 10 ple~ulG and lelll~ Lul~. In that a composite tube does not have the abra ion l~ "~e qll~liti~c of steel, there has been a need for a composite tube with an outer surface m:lt.~ri~T
that reduces al~ld~ive wear to a drilling sub or casings caused by contact with the borehole.

Con lu~Live fibres such as carbon provide cle~ n~tic ,chi~ 1in~ and are often used to enhance the ~hit~l(ling capabilities of inclll~ting plastics. For example, the addition of carbon 15 fibre to nylon hlcl.,ases signal ~ ion Accordingly, in that it is known that the choice of carbon fibre as a material for a rel,.ru~ g m~flillm is ~e~ .f ~ l to the object;ve of EM
Ll~l~yà~ ;y, there has been a need for a cu -l~Jo~iLe tube design wherein the design f~ it~tes the use of carbon fibre while providing ~rc~ ble EM 11aIIS~:e 1~;Y.

Accul.lhlgly, there has been a need for a composite tube design wherein the composite 20 llli~;lu~Llu~;Lul; provides both physical strength and an ~rc~y~l lc EM L.~ .G..~;y to permit the use of sensing e~ ....- -.l from within the tube.

Still further, there has been a need for a cu...~,o:,iLe drill sub with a composite structure which ~ nr~s the stiffn~oc~ of the drill sub while also h~ ovi.,g the abrasion fe~ r-e and ele~ tla~ ;y of the drill sub. Acco-di~ ly, there has been a need for~5 binder cu~ osilions which are cement based which enable the ~ ion or partial m of carbon fibre from the culll~USilG s~u~ e through ~ A~ g the ilir~ of the co"~yosiLG drill sub.

A search of the prior art has revealed that the above problems have not been addressed. For example, US Patent 5,097,870, US Patent 5,332,049, US Patent 5,398,975 and PCT
30 Publication WO 91/14123 teach composite tube structures. US Patent 5,250,806, US Patent 5,339,036 and US Patent 5,128,902 teach various a~y~ and meth~ for collecting I CA 02237432 1998-0~-12 . ' ';.' ~

downhole data. Canadian Patent ~pplication '~04~.62~ discloses a me~hod t'or reducing noise in drillstring signals.

Still further~ U.S. Patent ~,968,5~5 discloses a composite structure utilizing a prepreg construction, U.S. Patent 5, ' 1',~95 discloses a composite shell for protecting an ~ntenna of a S formation evaluation tool, U.S. Patent 5,132,62~ discloses a method ~nd apparatus for insulating electrical devices in a logging sonde, U.S. Patent 5,13g,~ 13 discloses an electrically insulative gap sub assembly for tubular goods, U.S. Patent 4,592,~21 discloses sucker rods which include a plurality of unidirectional reinforced composite fibre rods and U.S. Patent 4,504,736 discloses a gamma ray spectral tool for borehole use.

SU~ 7~A~YOF THE IA'YElVTIOlV
In accordance with the invention, a composite body is provided having signal attenuation properties for a physical and performance design point, the composite body comprising a plurality of fibre layers impregnated with a binder, wherein each fibre layer is selected from fibre materials having different mechanical and signal attenuation properties and wherein each 15 fibre layer is orientated with respect to a reference axis in accordance with desired mechanical, signal attenuation and phase shift properties of the design point.

Preferably, the fibre layers include any one of or a combination of fibreglass fibres, aramid fibre and carbon fibre wherein the carbon fibre is oriented at +10~ with respect to a reference axis to minimi7.o signal attenuation and the binder is an epoxy resin. In another embodiment, 20 the binder is cement selected from any one of or a combination of portland cement, portland-aluminous-gypsum cement, gypsum cement, aluminous-phosphate cement, portland-sulfoaluminate cement, calcium silicate-monosulfoaluminate cement, glass ionomer cement, or other inorganic cement.

In a preferred embodiment, the invention provides a composite tube for use in a drillstring, the 25 composite tube comprising a plurality of resin-impregnated fibre layers of a first type and a second type wherein the first type layers are interspersed by layers of the second type, the composite tube adapted for receiving a logging tool.

Preferably, the first layer type is ~,vound at + 10~ with respect to the longitudinal axis of the tube, the first layer type comprising 0-50% high modulus carbon fibre, 0-50% aramid fibre and - - A~E~ )E~ SlIEET

CA 02237432 1998-0=,-12 ~/1 16-50% high strength fbre glass and the second layer type is ~vound at 90~ with respect to the longitudinal a~cis of the tube, the second type comprising 100% hi2h strength fbreg,l~ss In another form, the frst layer type constitutes 90% of the total ~vall thickness of the tube ;3nd the second layer type is equally interspersed through the tube ~vall at 1-9 discrete radial 5 positions In a specific forrn, the invention provides a composite tube wherein the first !aver type is wound at + 10~ with respect to the longitudinal aYis of the tube, the first layer type o~ S~

s co~ g 25% high mn-hllllc carbon fibre, 25% aramid fibre and 50% high strength fibre glass.

In a another forrn, the composite tube has a signal ~llrl....l;OIl response of at least 70% at 20 Khz and a microstructure with a fibre volume fraction of approxim~tely 60%.

5 When used in a drillstring, the tube is ylcrelably 7-31 feet long and meets the yc;lr~ u~e requirements detailed in Table 1 in~ fling tensile load, cùlnyLes~ive load, torsional load, internal pre~ e, cndul~lce limit, lateral ~I;rr..~c~, impact strength, tensile strength, and yield strength which meet or exceed the ~l~ldalds of the ,~m~ril~n Petroleum TncSpecifir~tion 7.

10 In another form, the composite tube further culllyli~es an abrasion l.,~ coating on the outer surface of the tube and/or the resin-iull~l~,gllalcd fibre layers include a ceramic powder blended with the resin.

In another yLef~,lled form, the cc,~ osiLe tube further comrric~c end-fittings int~gr~lly :lttzlrh~.~ to the co~ o~ tube by additional fibre layers and resin and/or cement.

15 Pref~,~ly, the end-fittings include:
a tube seat for seating the end-fitting within the basic con~yosiLe tube;

at least one cu~uy~ ion bearing surface for supporting a colllyles~ioll load between the end-fittings and the basic Colly,o;.ilc tube;

at least one torcion~l transfer surface for l~al~L~lh~gtor~cit~n~l load between the end-fittings and the basic colllyosile tube;

a bending stress transfer surface for S~ Jullillg a bending stress load between the end-fittings and basic culll~o;~iLt~ tube; and at least one axial tension surface for ~llyyolling an axial tension load between the end-fittings and basic culll~osiLc tube.
In a plcrtlled form, the torsional transfer surface~s) culll~ cs eight surfaces which are either parallel or tapered with respect to the ll~n~itllriin~l axis of the end-fittings.

P.~r~ldbly, the end-fittings are ~tt~rhPd to the basic composite tube by ~ tion~l winding of binder-impregnated fibre and where the 3~ itio~l whl Ihlg is high mo~ s carbon fibre wound at 90~.

In a still further form, the end-fittings further coll~lise stabilizers which may include rutile 5 or ~hcoln~ ru-;usshlg lenses for use with micro pulse imaging radar.

In a still further form, the cc,lll~o~ile tube/end fitting junction is pre-stressed or pre-loaded to reduce the ~usce~l~bility to fatigue damage.

In a specific form, the invention provides a drillstring nlt;llll,.,l having a composite tube middle section with integral end-fittings, the culllposil~ tube middle seceion having a signal 10 Ll~ ;y CCl~ illg;

a basic colll~o~iL~ tube, the basic composite tube in~ 1ing a plurality of binder-hll~legllilled fibre layers of a first and second ty-pe wherein the first type layers are hll~ c.~cd by layers of the second type and the first layers are wound at i 10~
with respect to the longit~ in~l axis of the tube, the first layer type Culll~ lg 40%
high mn~l~lhlc carbon fibre, 44% aramid fibre and 16% high strength fibre glass and the first layer co~ e~ 90% of the total wall thirl~n~.c of the tube and wherein the second layer type is wound at 90~ with respect to the lon~itlltlin~l axis of the tube, the second type Culll~ illg 100% high strength fibre glass equally hl~er~ ed through the tube wall at a plurality of discrete radial positions;
end-fittings, the end-fittings inrlll-1ing:
a tube seat for seating the end-fitting within a basic composite tube;

at least one colll~l~,;,sion bearing surface for ~u~(JlLing a culll~les~ion loadbetween the end-fittings and the basic co~ o~ile tube;

at least one torsional transfer surface for ~l~Ç~lillg torsional load bGlwt;en the end-fittings and the composite basic tube;

a bending stress transfer surface for :~UIJ~JOlLillg a bending stress load between the end-fittings and basic colll~)o~iLe tube;

i CA 02237432 l998-05-l2 at least one axial tension surface for Du~olLi.,g an axial tension load between the end-fittings and basic cu-~.~osiLe tube.

In another embodiment of the invention, a method of forming a composite tube wi~h integral end-fittings is provided Co.l~l;Di..g the steps of:
a) winding a basic inner tube of a binder-.~tllratP~1 fibre on a steel mandrel;
b) curing the binder to form a cured tube;
c) removing the mandrel from the cured tube;
d) cutting the cured tube to length to form a basic tube;
e) inserting an ~lignm~nt mandrel within the basic tube and seating end-fittingswithin the basic tube over the ~lignm~nt mandrel;
f) winding an outer layer of binder-.~ d fibre over the basic tube and end-fittings to form c~Jlll~osile tube with end-fittings.

In another embodiment, an adhesive coating is added to the outer surface of the composite tube to increase wear r~ e.

15 Further emobi...,..lD of the invention provide for pre-DLI~shlg the c~,..l~,oDil~/end-fitting junction by methods such as c~ .e.,Di-.g the cured tube and end-fittings during Wl~lppillg and curing of the outer fibre layers, e .~ the co~-ffi~i~nt of thermal eYr~n~ n of the composite tube is less than the coeffirient of thermal . ~ of the end-fittings wherein during Wla~illg and curing of the outer fibre layers a colu~ DDi~e force is inducedl on the 20 end-fitting, ~ rtin~ the end-fittings to receive a lock nut for Lll~allillg a conl~-resDive force on the composite/end-fitting junction or providing end-fittings which include an inner and outer end-fitting adapted to impart a co---~-~,.,si~e force on the con~obiL~/end-fitting jun-~fion PRIEF DESCRIPTION OF THE DPAWlNGS
25 These and other features of the invention will be more a~J~aLell~ from the following description in which L~Ç,l~lce is made to the appended drawings wherein:

Figure 1 is a graph of phase shift vs. frequency for a number of basic composite tube samples on a log x, linear y scale;

Figure 2 is a graph of signal ;~ /;on vs. L~ u~ ;y for a number of basic C
tube samples on a log x, linear y scale;

Figure 3 is a close-up view of the graph of the results of Figure 2 norm~li7Pcl to a 2.5"
working thirk~n~c~ showing signal ~ttPn~tion vs. frequency for basic composite tube samples on a linear x-y scale;

Figure 4 is a graph of the results of Figure 1 norm~li7.o~1 to a 2.5" working thirkn~
showing phase shift vs. frequency for basic colllposiLe tube samples on a linear x, log y scale;

Figure 5 is an assembly drawing of a coln~o~ile tube and end-fittings in acco,.l~lce with the invention;

Figure 6 is a cross-sectional drawing of an end-fitting in accold~lce with the invention;

10 Figure 6A is a cross-sectinn~l drawing of the end-fitting of Figure 6 at the line 6A-6A;

Eigure 6B is a cross-sectional drawing of the end-fitting of Figure 6 at the liue 6B-6B;

Figure 6C is a cross-sectirn~l drawing of the end-fitting of Figure 6 showing pl~r~ d r~im~n~ions for a nominal 6 3/4 - 7 inch tool;

Figure 7 is a drawing of an assembled composite tube with end-fittings in acco~ lce with one embodiment of the invention showing a logging tool within the body of the assembly;

Figure 8 is a torsion load free-body tli~gr~m for the design of the tor~ue transfer surface(s~.

Figure 9 is a cross-sectional view of a co...l~o~;~e tube/end-fitting assembly in which the end-fittings include an inner and outer end-fitting;

20 Figure 9A is a partial cross-section~l view of another embodiment of a composite tube/end-fitting assembly in which the end-fittings include an inner and outer end-fitting;

Figure 10 is a partial cross-sectional view of a composite tube/end-fitting assembly in which the end-fittings include a lock-nut;

Figure 11 is a partial cross-sectional view of a co~ o~ile tube/end-fitting assembly in which the end-fittings include an inner and outer end-fitting;

Figure 12 is a ~;onlpali~ùll of a gamma ray log of a section of a wellbore c~ ' ;ug a conventional wire-line log with a logging while tripping log;

DETA rr F~ DESCRlPTlON OF THE INVENTION
It has been discovered that the eleckom~nptir c.;lr....-l;on properties of a co.ll~uDile body are affected by the o.i~ ion of the fbre layers con.~ g the body, thus p~ iug the design and construction of colll~o~iLe bodies which heretofore have not been suitable for particular applir~tinn.c.

As indicated above, it is known that the use of high mn~ carbon fibre in a coll~o~iLe body affects the ele.;L~ "~.~r~ic ;.llc~ ion properties of the con,~osiLe body. It is also 10 known that materials such as fibreglass and aramid fibre do not xignific~ntly affect these properties. For particular applications, high mnflnlll~ carbon fibre has superior strength and ~c~ro~ a.lce cl~ ;Leli~Lics over fibreglass and aramid fibre and is, accoldillgly, well suited for certain applications. Thus, in the past, where it is desirable to provide a colllposiLc body having ele;Ll. ~ gnP.tic L1~L~ ;Y properties, the use of carbon fibre is ...;,li",i,.~d 15 However, the design of a colll~.osiLc body with p~rtirlll~r strength andtor ~.,LrUlll~lce properties within particular physical ~limPn~ n~ requires that the culll~o~iLe body meets or exceeds the design co~-litinn.~ while l~ i..i"g within the size restrictions. Accoldill~;ly, with the intro-hlction of ~tlrlitir~n~l p~la.ll~Lr.)x, such as minim~l elecL~o~ signal ~llr.."~l;nn, it has previously been con~i~lered that the use of a hlown ;1llrl~ g n~t~.ri~l~0 such as carbon fibre must be ...i~-i---i,.P.d or e~ d in order to meet this elecLlo~ gnp-ti c ;o~ design le~uil.,lllc,lL. However, in certain application~, in view of the physical size l~ uil~,lllcnL~ of the co~ 3O~iLe body and/or the strength/physical perfonn~nce le.luiic~cllL~, the use of carbon fibre cannot be Plillli~ d while still meeting the strength/physical pelrul.llal~ce re4uhc~ ,.lL~.

25 In OVclCOll~illg this problem, the subject application has recognized that the carbon fibre oricllL~Lion within the composite body is related to the ele-;Ll..",~gnP.tic ~ ;on properties of the cullll~osiLc body, thus rendering it possible to design a colll~o~iLe body with the required high strength/physical size limh~tion~ while also achieving the desiredclecLl.)..".gn~tir ~l~r.lll~l;on properties.

30 In particular, the subject invention has recognized that the orientation of carbon fibre within a cr)mpn~itP body and, in particular, a culll~Osi~c tube enables sensing e..~ .".~."l utili73ng clccll.)...~gnPti-~. sensors to be placed within the collll)o~iLe tube which provide an acceptable data arqui.cition signal. F.~se~llti~11y, by diD~c,billg the carbon fibre with glass fibre in conjunction with a low WI~ g angle, a highly conf1~rtive annulus of conductive fibre is avoided.

In a specific application, this invention has developed a co.l,~oDile/metal tube for use in a 5 ~lri11~tring for downhole drilling operations. With this design of col",~oDile/metal drilling tube, a s~.,. .~eA design is provided with end-fittings on either side of a coll~osile middle section. The end-fittings enable integration of the composite/metal drilling tube to an existing steel ~lri11.ctring while the composite middle section enables the pl~rc ~ and use of logging while tripping, logging while drilling, IlleaDu~ cll~ while tripping and lO ,llcaDu,cl~lclll while drilling e~ .l within this section. In order to permit the use of logging or meaDul~ l e~ , the c<Jlll~oDiLc middle section has an acceptable elecLlu~ g,~;c transparency in the range of OkHz-2001~Hz.

Accordingly, the design of a composite tube with integral end-fittings for use in a ~lri11.ctring while having specific ClC~ .. 5g.. -1;C properties, requires the Co",~uDilc tube section to have 15 both the physical strength, perf~ e and size char~t.ori~tics of existing steel drilling tubes (as per API b~ecir,calions, where applicable) as well as the required elc-;Llu...~gnPtic properties. Fulll,cllllu~c, the composite tube with integral end-fittings must provide a cu~ ,osile/metal junction which provides optimal p~lçu~ e cllal.Lcl~,liDlics, primarily a s~ti~f~tory durability in the high stress drilling t~llVil~.llllllClll.

20 The colll~oDiLclmetal tube has the following components:
1. the basic composite tube;

2. the end-fittings; and, 3. the junction between the basic composite tube and end-fittings.

As i...li~ in addition to the physical strength ~ c~ s of the composite tube, 25 cle~ gnPtir l,dnDpàlell.;y properties are also required to permit logging e.~ ....r..l to errcclivcly record downho}e cil~r~rteristics. Reduced signal ~ l ion provides superior data ZC~ ;til~n Primarily, clc~ gn~ti~ aLcllcy is required in the 20kHz range, however, reduced ~tt~nn~tion in the 0-200 kHz range is also useful.

30 Logging C-IUi~Jlllclll may include both electrode devices and/or in~ r$ion devices to obtain i,lro",~lion from the formation. Electrode devices require direct contact with the mildly conductive borehole mud to inject currents into the formation. When me~.ulc~ . are pelrulllled in lower con-lnctivity air-filled or oil-based boreholes, conventional electrode-based mPthnf~ are not possible. As this .l-ca.urel,.c~lL method is limited to direct contact with a borehole mud, lll~,&.,ùl~llle.lL~ through neither a highly COl~du~,live all-steel drill sub 5 nor a composite drill sub are possible.

An in~ ction device on the other hand lllea;,ul~,s the formation co~ ivity through the use of ~eCu~ ,y eddy currents induced into the form~fi- n This lllea~7ul~ lelll is superior in lower crnrlllrtivity air-filled or oil-based boreholes and it can also tolerate the more typically ellc~ullL~lcd mildly con~letive mud envil..JIll~ . Tn-ln~ticm logging has proven 10 to be very versatile and today forms the primary means of evaluating formation le.ibLiviLy.
As in the case of electrode devices, llle~uLelllellL7 are not possible through an all-steel drill sub but are possible through a mildly conductive CGlllL)OSiLe sub.

In the basic induction device, a C~ .L~ult amplitude and fie~luell-;y a~ I;"g current is fed to a l.~n~ coil. The resultant m~nPti~ field produced around the Ll~ . coil, 15 induces eddy current flow in the formation. AA.~.. ;.. g a cylin~lrir~l ~.yllllllèlly, the eddy currents will flow in paths coaxial with the borehole. The eddy currents induce an ,.I;..g voltage in the detector coil that is a full 180~ out of phase with the ~ e current. The magnitll-le of the eddy currents are plvpo-lional to the conductivity of the rOlllldli~ll.

20 The lei,i..live colll~vne..L of the detector signal, forms the basis of the in-1nctir)n eclsul~llèlll~ A 90~ out of phase direct cv~ g signal is also received by the detector coil but is electronically filtered out.

Current inrl~lrtir.n devices dPsignP~ to lll~ Ul~ the ~si~.Livily (in ohm m) of a forn~ati-~n, typically operate at a frequency of 20 kHz. The formation resistivity has been trarlitionally 25 doe~ d on hard copy over a four decade print out range; from 0.2 to 2000 ohm m.

Furthermore, the use of composite ma~Pri~l also allows for the use of acoustic ~and rec.,;villg devices to take nlea~ul~llellLs of the well bore ~ e~ This includes, but is not limited to, the imp!~...~..l~l;on of acoustic t~ ...ill;..g and receiving devices used to l..c~.u.e the acoustic impulse travel time through the formation immP li~tPly ~dja-~Pnt to the 30 bore hole. This travel time, At, the specific acoustic time, varies accol.lhlg to mineral colll~o~ilion, porosity, and the fluid present in the formation (in situ). Accordingly, further data, such as rock or ~P~ lc~l properties, location of fl~clul~,s can also be obtained.

CA 02237432 l998-05-l2 Tm~in~ using acoustic reflection data is also possible. The propagation of acoustic waves through composites and co~ ;on for the cu~ o~iLe acoustic ~lu~ lies can be undertaken - yield~ng the above whereas propagation through steel pipes is highly problematic.

5 Still further, the low density of the composite m:lt~ri:~l allows for ~ u e~ transition of gamma/llcullull/beta m~t-ori~l~ ~rough the body of the sub ~ereby allowing for more ,",,~ tf-ctjnn of same with IGceive-~ located inside the sub.

Design of Basic Co"~o~lle Tube The basic design of the composite tube requires low moisture absorption, heat ,~ e, 10 and corrosion resi~t~n~e. The culll~o~ile tube must also show the ",~rl.~,~;f ~ elrullllal~ce ûf an existing all-steel design as shown in Table 1. ~1c~ tinnc whic~ follow refer to a nominal collar size of 6 3/4 - 7 inch. It is lln-k.~lood that sîmilar ç~lr~ tions may be applied in the design of tools of di~;~llL llim~n~inn~.

Table I - Required r~,.rO, ~ce C*u,acl~ hcs (nominal 6 3/4" diameter tool 15 only) tensile load, max 200,000 lb. static 800,000 lb. impact Cv~ cS~iv~ load, max 50,000 lb. static 300,000 lb. impact torsion load, max 50,000 ft-lb.
intern~ u~e, max 10,000 psi endurance limit 75,000 psi lateral stiffnp~s~ min 70% of steel drill collar impact ~L~ ;Lll, min 40 ft-lb charpy v-notch at ~llbiellL temp.
tensile strength, min 120,000 psi yield ~ h~ min 110,000 psi physical ~lim~n~ions, OD, max 7.25 inches ID, min 2.25 inches overall length, max 31 feet 30 ~aLillg L~ laLùl~, max 300~F

Basic lube Const~c~ion A basic cu~ JosiLe tube was prepared by a cu~ ltl controlled fil~mrnt winding process.
This process adds successive layers of a binder~ aL~d fibre over a steel mandrel to build the basic tube. The winding speed, spool location and spool fibre are controlled to S enable the fibre, the fibre Oli' ..l~ .n and thirkn~ to be controlled to build up ~"cce~;v~
layers of fibre in accordal.ce with the desired end-product .'h~ rs. Generally, the fibre and fibre orientation are selected in accorddllce with the physical and ele~;Llo..~ ir properties of the design.

Binders are preferably either of organic or inOlgi~lliC composition. In the specific design of 10 a composite tube for use in a tlrill~trin~, there are two main types of fibre layers in the basic composite tube, the first type being a low angle wrap (for example, ~t 10~ off the lnngihl-lin~l axis of the tube) and the second type being ~;h~ elllially wrapped around the tube (90~ to the kmgih~in-~l axis of the tube). Each layer is wrapped with one half of the fibre aligned at its positive wind angle and the other half at the negative wind angle.
15 The first layer may comprise a number of dirr~ fibres within that layer such as carbon fibre, aramid fibre or fibreglass. For a given design having an elecll.,...~gn~oti~
Lldl~7~al~,.l.,y, the amount of carbon fibre is ...;..;...i,~d while still pk'~ â given physical strength. The second layer type may also co"l~lise a number of dirr~ fibres within that layer. However, if the design requires electr~m~n~tir Llal~dl~ y, carbon 20 fibre would not be ;~ e~l in this layer.

Preferably, the second layer type is equally i..lr.2~ -;.ed through the composite tube wall at a number of discrete radial positions in order to i,llprove the strength of the composite 1~..,;,. 1~.

The binder may be either a cement based composition or a sL~wldaLd epoxy resin.

25 Cement-Based Binder In the situation of a cement based c~)lll~osilion, the use of a cement based composition eli~ ..lr~ the need for high mn~lnlllc carbon fibre for a signifir~nt portion of the drill sub ~ enabling the repl~rrml~nt of the carbon fibre with high m~ hl~ aramid fibre.

- The cement may be selected from any of one of or a selecti--n of a portland cement, 30 portland~ u~-gypsum cemrnt~, gypsum cements, ~hlminml$_l)ho~l,h~ CPn1lPn portland-sulfoal.. iu~l~ cements, calcium silicate-monosulfs~ le clom~nts, glass ionQmtor cements, or other hl.,l~ dllic cements.

Terhr;1llPe for the hlcol~ulalion of a cement based culll~o~-iLion include coating glass fibres with an aqueous slurry of the cement composition as they are wound around the steel mandrel and thf i~edrLf l air-curing. AlL,llldlivcly, the cement composition is added to the glass fibres during winding by placing a negative ele.;llvsldlic charge on the fibres and S passing them through the cement composition which has been charged to cause it to adhere to the fibres. In this situation, the cement cu~ o~.ilion is ~lef~..dbly fl~ i7P~1 and passed through a polarizing grid to provide the cement with a positive electrostatic charge using known flui~li7ing terhniquPs~ A voltage dir~r~llLidl of about 20 kilovolts is pl~,~.red.
Alltliticn~l cement may also be added after whldillg with water or steam being added during 10 heat curing in an autoclave.

The cement based binder is used to build a collll)o~ile tube where it is desirable to impart a high degree of stiffnf ss to the drill sub which may allow for either the reduction or fl;~ i.JI~ of carbon fibre within the tube. As in(lir~tP~l, the reduction of carbon fibre from within the tube will improve the Lldl~7~al.,1l.;y for ele~ .",~nPtic signal and/or field 15 plupa~,dLion at a range of freqnfnriP~e. FUIL1I~ IIOIC, the use of a cement binder may is also used to improve the abrasion l~e~ e of the drill sub as well as lowering the density of the tube which is adv~nt~f-ol~e for particle-based sensing e-lui~lllcllL~

Resin Based Binder A standard epoxy resin may be used as a binder. Evaluation of a specially forrmll~tP~ resin 20 exhibiting low electrical dl~f~ -l;on properties was evaluated in a sl1ksc~l~ test ~C.,illlG,l and was found not to offer eignifir~nt benefit in lowering the elrctrirz~l dl~ n over ~he standard epoxy resin binder. The specific resin used for the test samples was a bi~h~llol F
resin with a MTHPA curing agent.

The layer thirknPee is typically between 0.01 and 0.040 inches. For the specific drillsking 25 tube, the layer fhil L ~ S of the first type layers are 0.038 inches and 0.035 inches for the second type layers.

Curing is ccm~lllrt~d as soon as all the fil~mrnt winding is complete in a convection oven.
The cure srh~ lle follows the resin ..~ lr;~ IG~ co~ lP~d L,.ocelul~. A typical cure consists of ~ ;"l ti~ g the oven ~GIIIlJGld~UlG at 180~F for 4 hours, raising the lGlll~J~,ldlUlG
to 225~F for 4 hours, raising the tGlll~)ela~UlG to 300~F for 6 hours, turning the oven o~f -and allowing the part to cool slowly to room IGlll~)t;ldUlG in the oven.

After curing, the mandrel is removed and the inner tube cut to length.

The baseline design for the c~ll~o~ile tube used Grafil HR40 carbon fibre (Courtaulds Advanced M~tf~ri~lc, .S~ Q, CA), DuPont KevlarTX 149 and Owens-Corning E and S-2 glass. The tube was r~lic~led with a number of l~min~te layers with thi~ ,c and fibre o~ i(m angles as shown in Table 2. Table 3 shows the m~rh~nir~l properties of the baseline fibres. The rèsin system utilized for the baseline design was Shell's DPL 862 resin. Other fibres which may be used include 3M Nextel~, a ceramic fibre. Other resins may be used such as the Bryte Technologies Inc. EX-1545 RTM System.

Table 2 - Rn~elj~2e Composite Tube ~t~ri~l Angle % Thickness HR40 Carbon Fibre 10~ 36 Kevlar 149 10~ 40 S-2 Glass 10~ 14 S-2 Glass 90~ lQ

Table 3 - Fibre ~v~ ies 15 TYpe M~ r~ L Tensile Modulus~ msi Tensile Stren~th. ksi HR40 Carbon Grafil, Inc. 55.3 700 Kevlar 149 DuPont 26.0 500 S-2 Glass Owens-Corning 12.5 530 L~eral Stiffness 20 The ~ f!. - ;I~g of ''stiffn~c~ of a co~ osiLe logging collar is accomplished through the use of a plurality of fibres which may be selected from but are not limited to carbon fibre, aramid fibre and glass fibres. The orient~tion of these fibres and relative ~ ; used of each and the selection of organic and/or h~ gallic con-~osiLions used as binders control the ,~,;rr..fcs~

Standard oil field practices call for drill collars, subs, motors etc. to have a ~ rr..~sc equivalent to 70-80% of a bar of solid steel of the same ~1i~ . For example, a 6.75"
~l;;.. ~el drill collar must be 70-80% as stiff as a solid bar of the same steel at the 6.75"
.li~",~le,. This ~lirr,,~cs ~ uil~lllellL is required to allow the driller to control the direction 5 of drilling. This is achieved by the driller being able to the colll~les~ional load on the drillbit. The colll~.lcssional load is controlled by reducing the tension held on the drillsking by the driller using the cabling system and derrick to partially lift the tlrillctring from the wellbore in conju,lclion with the use of drill fluid to float the ~lrillxtring.

Thus, by contolling the conl~l~sDional load on the lower sections of the drillstring, the 10 dril}er is able to control the direction in which he is drilling by ~,.x.-. i"g that the lower section has an "equivalence" throughout its culll~ullclll with respect to stiffn~cc.

In applications where a high degree of ~I;rr,,~x~ is required, higher amounts of carbon ~lbre and/or illOl~;~lliC binders are required in order to stiffen the sub. In the situation where less D~;rrll~ss is required, such as horizontal drilling, it rnay be possible to el;"~ carbon 15 fibre.

Thus, while lateral XI;rr~cx is not specifi~d by APISperffl~ti~n 7 or RP7G and as in-iir~ted above, uld~ da~ds would require a Ill~ lateral stiffness of 65-70% of a similar steel section in order that directional control of the drillsking is ll.~ .i".od Thus, in a-l~litif-n to the Le~lui,c.ll~-lL~ set forth in table 1, the composite tube was ~ $ign~d with a 20 lateral ,,lirr.,t?Cx of 70-8097o of a similar steel section with the required inside and outside .1;,.l". t~,x of the tube, namely 2.25 inches"..;..;,."l,~" and 7.25 inches",.-~.i"~
leD~Iively. Accor.lhl~ly, with a lateral Dl;rr..~~~x of a steel section of 2.9E91b-in2 with a 29 msi (axial m(~-hllll~ of steel), the ...;~;"~ . stiffn~cc of the composite tube is 2.03E9lb-in2.
With a 7.25 inch outside .1;;..,.~11 . and 2.5 inch inside ~ ."~ , the 111;11;11~11111 axial mn~ lc 25 must be at least 15.1 msi.

A baseline tube design was d~ocign~-d having an axial modulus of 17.8 msi.

Stress and Strain Analysis of Basic Composite Tube The basic cu~ GDile tube was analysed for stress and strain under a c~"lll,i"ed loading cumliliull of 800,000 pound axial tensiûn load and a 50,000 lb-ft torsiûn load. The l~min~t.o 30 design at a section away from the shaft end was analysed using rl~Q~ir~ min~tion theory.
A ~les~rirti~-n of this analysis is found in Mech~nirs of Composite Materials by Robert M.
Jones (published by McGraw-Hill Boûk C~-)mp~ny, 1975) and was used to tl~termin~ layer stress and strain state under external loading con~iti~n~. The analysis provides a point stress analysis of a l~ under in-plane loads. The lh~..;..~le col~lilulive relation is forrmll~ted and is used to ~ o rnid-plane strains and ~ v~ules which arise due to in-plane loads. The mid-plane strains and L;ul~alul~ are then used to ll~f~rmin~ the layer S strains and, therefore, the stresses in each layer of the l~ e. The loads used in the program are input as running loads. The axial and torsion running loads for the composite body are r~lr,~ t~d below.

Only the composite material within the zone 5.25 inch inside .li .. ~ to 7.25 outside m~ter was used in the following analysis. The material below 5.25 inch .i;~.n~l~,), was 10 con~ red to only provide co~ s~ive load carrying capability.

Axial R' ~. ~ g L.oad, Nr a = load/area N~ = at=load*th;~nP~/area at 800,000 lb. tensile load 15 N" =800,000(1.0)/19.6=40,816 Ib/in.
Torsion R-~nning Load, Nry a = Tr/J
T = Torque r = Average radius 20 J = Polar .. ~.. 1 of inertia N,~, = at = T/2~ t = wall thi~ n.o.
at 50,000 lb.-ft N,~, = 50,000(12)/(27r(6.25/2)~) = 9778 Ib./in.

The m~t~ri~l properties at a shaft section away from the metal end-fittings are ~lc,S~ t~d in 25 Table 4, the design allowables are presented in Table 5. The stresses and strains from the CA 02237432 l998-05-l2 combined axial and torsion load are shown in Table 6. Note that all margins are positive under these loads.

Table 4- Ma~erial Properhes of the Composite Body Axial Modulus 17.8 msi 5 Hoop Modulus 1.81 mAsi Shear Modulus 1.09 ATnSi Poisson's ratio, AH 0.47 Poisson's ratio, HA 0.048 Table 5 - CL , : ~~e Design Allowables HR40 Kevlar 149 S-2 Glass 0 Tensile strengt* fibre direcfion, ksi 210 200 200 T~u~.. ,.~,.,e tensile strengt*, ksi 6 4 6 C~ .;.;,e strength fibre direction, ksi 100 60 100 T~";,.. ,~e ~ e strengtl~, ksi 30 30 30 Shearstrength, ksi 9 3 9 Bearing ulti1nate strength, ksi 60 60 60 TABLE 6 - SUMMARY OF STR~,~,S~

10~ Layers HR40 Kevlar 149 S-2 Tensile stress, fibre ~irection/allowabte, ksi 120/210 57.4/200 27.4/200 Tensile stress, Iru~ 3e ,li/ i. /allowable, ksi 1/6 .6/4 1.3/6 S C~ ,, . t~D~ C stress, fibre direction/~ e, ksi 0/100 0/60 0/100 ~ ....... e stress",~ e ~ llv~ OE, ksi 2/30 .8/30 .3/30 Shear stress/allo ~ , ksi 6.8/9 2.4/3 8.~/9 90~ Layers HR40 Kev~r 149 S-2 Tensile stress, fibre direction/all.. Ie ksi 0/200 0 Tensile stress, transverse direction/~ l~o............ ~ ~ 'e, ksi 3.7/6 e stress, ~bre direction/allv....................... 'le, ksi 7.2/100 C. , .. ;.. ~.5 ' stress, I,.. "_,.,e direction/~7r .. Ie ksi 0/30 Shear stress/~ '~ .. . Ie, ksi 8.3/9 Next the column buckling of the composite tube was examined using 15 Eulers formula for pin-ended columns.

Critical Pfl~r~ g Load, Pcr P" = ~r2EI/L2 E = A~ial Mo~
I = Moment of Inertia - 20 L = Length ....;,.g a composite body length of 235 inches;

P~r ~ 7r2(2.03E9)/2352 = 362,000 pounds.

The .. _xi.. ~.~ cu~ si~e impact loa~ is 300,000 pounds.

El~.,h_ ngnetic Transparency Testing of t*e Basic Composite Tube 5 Tube Sarnple A was ~;u~ ;L~d as a control to compare variations in design with respect to the expected a~ ;ol. and phase response. Tube A also served as a reference in the m~mlf~t~tllre of the test d~,~alus.

Tube Sample A was a 100% carbon fibre co.l.~osiLion, co~ ;d from Grafil HR~0 fibre, which has a lower conductivity in co~ a.ison to Grafil carbon fibre. As well, the 10 HR~0 fibre has inferior ....o~ h~..;cal properties making it an hld~.~liale choice for an I~M
Il dll~p dl cllt tube .

Tube S~mrle~s B & C were constructed from the "~c~ y superior Grafil 55-500 fibre of varying pel~ dge c~ inns. The carbon fibre wrapping during construction was c--nfin~ to the coaxial (ie. ch~;uu~l~lllial) oriPnt~tion 15 Tube Sarnple D was constructed of Grafil 55-500 carbon fibre with the coaxia} carbon fibre Wld~l~illg reduced to the ...;..;...~.. allowed by the mP~h~nir~l p~,lr..,...~ e c~

Tube Samples E & F are duplicates of Tube Sarnple D but with dirr~,lillg resin properties and a reduced carbon fibre ~ ;t;lllage c-~ ;on Tube Sarnple G was col~llucLed with half the carbon fibre p~ dge c~ r~ ,. ion over 20 the previous tube samples; E and F. Kevlar~ fibre was ~ub~Lilule:d for the carbon fbre that was removed.

A SUlllllldl,~' of the construction of these tubes and a ~u l~llla~y of the electrom~n~tic testing results is shown in Table 7.

CA 02237432 l998-05-l2 Table 7 - Composite Tube Sample Construction; Attenuation and P~ase Shift Data ~orm-ulatiorz Sample S.~".ir~.t Carbon S- Fibre rrans- Signal Sig~tal Signal r~ Fibre Glass Kevlar 0, . mfssion Phase Phase Phase Degrees Coefficient Shift Shift Shif~
¢~20 kHz ~IOkHz ~20 a~70 Radians k~z kHz Radians Radr~ms A Cra,fil HR- 100% 0% 0% 45 74.73% 0.0192 0.0384 2.6~1 B Grafil 55- 75% 25% 0% 90 12.48% 0.3269 0.38~7 2.6233 C S Grafil 55- 55% 45% 0% 90 48.34 0.1691 0.2255 2.8195 D New Resin 73% 27% 0% 10 70.64% 0.0327 0.065~ 2.7490 E Old Resin 50% 50% 0% 10 76.39% 0.0000 0.0061 0.0000 F New Resin ~0% 50% 0% 10 74.88 0.0031 0.0062 0.0000 G ~vlar 25% 10% 65% 10 76.51% 0.0000 0.0000 0.0000 Testzng of t~e Cor~rosite S~ , les for In~r~ctinn Characteristics The test tubes were subjected to testing for their induction eh~r~rtt~ri~tic.s The test a~ala~us con~i~t~d of two coaxial encircling coils located on the interior n~ (el) and exterior (detector). ~ signal generator was conn~cte~i to the interior coil 5 and a con~ amplitude, variable frequency ~ac) signal was fed into the coil.
Mea~u,c,,lcnls of voltage and phase were taken from the exterior coil with ~crclcnce to the interior coil.

The skin depth equation describes the relationship between the amplitude and phase of an ac - signal as it propagates through a con~ ctive material. The eqll~tinn predicts that the 10 arnplitude will be ~ ed as an exponential function of distance and phase will be delayed (ie time delayed) as a fimrtion of distance.

CA 02237432 1998-0=,-12 W O 97/21117 PCT/CA96/~0768 Qu~ livGly the equation is e~ esscd as:

~ (skin depth in metres) = 1/(~r * freq. * ~br * ~0 * a)l~2 where. iL4r * ~40 = the m:~nrtir. permeability, where ~ is taken to be equal to 1 for cu~ osile m~t~ri~lc S and ~ = the m~tPri~l rr~n-lllrtivity in mho / m .J ~ I iQ11 = GA~t phase shift = cos(~t + distance / ~) expressed in radians The a~ on and phase shift of each sample were tested over a frequency range of 5 to 70 kHz.

10 Testing followed an iterative progression, where in each ~--cce~ive sample ...,..,.~r~ ..ed, mn-lifir~tion of the composite tube properties were directed towards ~.~h~nr.;.~ the ele~ u...~ .c l~ 7l~alGll~y at 20 kHz. The first few iterative steps served as b~ g the cu~ o~,iLGe tube properties.

Table 8 shows the results of ~ ~--;";-~n and phase shift testing con~luctec~ on the tube 15 samples. The results are based on the individual re;,~,ûl~,e of each tube and are not norm~li7rd to a fixed wolhhlg thir~nrcc. Table 9 ples~ , the results after norm~ ti~n to a working thicknlo.cs of 2.5".

o 8 8 O O 8 O ~ o8 o8 ~ ~ ~ 8 ~ 8 8 8 8 ~ ~ ~ ~ ;
r~ ~ o o o o o o o o o-o o-o o o o~o o o o o o ~-r~ ~ ~0 s O N C~ D ~0 ~.0 i~ r~ B
co Q 0:) ~-- CO ~ c~ 0 0 0 N Q o 0 ~ ~ CD ~ O ~ r c~ o o o o o o o o o o o o o o o o o o o o o o , o~
C ~ ~ D
~ 8 N ~ ~ ~ 8 ~ ~ ~; N ~ ~ ~ O _ ~ ~O ~ 8 ~
~ 8 8 8 8 o 8 o o o 8 o~ o o o~ o o ,_ ~L ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
E 0 ~D 0 ~D ~D ~ ~ ~ O ~ 0 N Q ~ ~ o ~ r u. o o o o o o o o o o o o o o o o o o o o o o ~
, ?~
~ 8 8 O o g o o o g ~ 8 o o o ~ 8 8 ~ ~ o ~ ~
o o o o o o o o o o o o o o o o o o o o o o ,I
c~ ~ ~ rN ~ N ~ ~ ~ ~ ~~ r- ~ ~ O ~o ul o o o O O o o o o o o o o o o o o o o o o o ~ U~ r-- oN ~N N CO o 0 10 ~_ C~ N ~g 2cor-~~ CD l_ ~D--~ o o O 0~ o O O O O O O O O O O -. _ N N ~o 1--o ~ ~ ~ ~ ~ ~ ~ ~ ~ o o O O o o o o o o o o N

E ID N ~~ ~~ rN~ ~O ~ D _ ~ D c~7 N 1~7 ~ _ r7 1 i O o o o o o o o o o o o o o o o o o O O o o O

0 ~7 t77 0 ~ ~ ~jD7 ~ Q ~ U7 N -- Q ~ 177 ~ 10 N ~D U7 r7 _ r~) ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ O O O O _ ~ N
E N ~ 0 ~ ~D ~ ~7 N ~ a7 N N cN~I O ;~ c~7 ~ 8 ~ ~0 n7 0 0 ~ ~7 ~7 ~7 Q7 c~7 ~7 it7 ~~ i 7 ~7 ~o7 ~ ~D io ~ ~ N _ O O O O O O O O O O O O O O O O O O O O O O ~

X7 Cr77 i 7 -- -- S Q7 . i D ~7 ~7 ~O N l_ ~Q ~~ N . --, 2~N
-- N ~O ~ N N N r7 10 ~0 ~0 ~ ~0 1IN7 tOD ~7 O N ~7 ~ ON CD
- m ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o o o o -- _ . _ N N

E ~ u cO ~ ~ ~ c7 o ~ ~ ~ ~ D ~ ~0 ~. ~
9 m O O O O 0 0 0 0 0 0 0 0 0 O O O O O O O O O -~ ' .

I_ U C~ N N ~ ~ r7 ~ ~ c~~, ~o, c~ ~ ~ uo c~7 _ N ct7 ~ ~D
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o o o o o o o N

n7 0 0 ~ cC ~ 7 ~ ~ Q c77 0 Q ~ 0 0 0 0 0 0 0 0 0 '9 I u~ _ _ _ I' r~ _ ~ N N N N N c~J ~ ~r ~r 8 ~o cD cD t-- , ~ ~

W O 97/~1117 PCT/CA96/00768 ~i _ ~ oooooooooooooooooooooo .
.o o t~ o O r ~ O ~, O ~ , z . . =
~ o ~ ~Z~ o ~ ~ ~ 8 G ~ o ~ ~
~ ~ ~ ~ ~ O O O ~ ~ ~ 0~ 0 0 0 0 0 0 0 0 o _ o~ o ~_ . u ~ _ a~ _ C~ ~ O ~, ~ ~ o o g ~ O g ~0 ~ gO ~ ~
lli ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
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~o o o o o o o o o o o o o o o o o o o o o o .~ N ~ N ~ ~ CO ~ o ~; o O O g -- .o o o o _ N

_ ~0~ ~ ~ 8 N ~ ~ ~ 8~ ~8 0 N ~ ~o ~ ~ N 8 g ~ o o ~ 8 ~ -Q O O O O O O O O O O O O O O O O O O O O O O

ID _ _ _ ~ N ~ OO _ ~ ~--cn ~ N N o ~ N UO
o o ~ N N N N N ~ 00 ~ N ~ -- ~ 0 O N -- ~~ tJ~ ~ o CO ~ ~ oo _ N o o 8 ~ ~ 8 8 <.) o o o o o o o o o o o d o o o o o o o o o o' I
~ ~ ~ ~ N j~ N
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~ ~ ~ N ~ ~ 1!0 ~ N 0~ ~ oN N 1~ ~ CO ~ O O 8 ~ ~ 8 ~ 8 ~ .
r m o ~ O O o - - -- - - _ - o g 8 o~ g 8 8 8 8 ~- ~

8 ~ N 0 1~ N ~ ~ ~ ~ 00 ~ O _ ~j~ ID 00 ~0 CO ~~ 00 0 ~ 5o ~On ~D N ~~q o~ ~ CO ~ ~ 0 ~ o o O ~ ~ ~. ~ ~~ ~O ~O O O o' o O O O O O O o N r~

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~ ~ ~, O ,., co ~ co _ ~ N N N N ~SNJ 1~ ~ ~ B ~

CA 02237432 l998-05-l2 Figures 1~ are graphs of the results of s~ l ;nn and phase shift for the composite tube samples. Figures 3 and 4 show the results nonn~li7P~l to a working thicknP~s of 2.5".
Figure 3 ~l~se~ a close-up of the nonn~ p~ P-~ on results on a linear x-axis andlinear y-axis scale.

5 Results There are three main pd~ S in the tube composition under investigation:

1. carbon fibre coaxial ~ nmPnf 2. percentage concentration of carbon fibre 3. c~ ;bulion of resin to con~l-lrtivity 10 The results show that in the case of Tube ~S~mplçs B & C, coaxial ~ nmPnt has a major contribution in .I~.",i,.i"~ the response of a tube sample. From Table 9 at 20 kHz, the on values are 0.1248 and 0.4834 re~e.Lively for Tube samples B and C. In Tube Sample D, the effect of coaxial alignmPnt was Ill;ll;lll;~cl and the l~:,pollse hll~lovtd to 0.7064.

15 C--"~ , ;uP the results of Tube Samples D, E & F, the red--rti--n in carbon fibre p~;~llLa~e col-r~..l.dLion improved the l~u.~e from 0.7064 to 0.7639. Fu~ llole, the phase shift response for Tube Samples E & F indicate a dramatic change in phase behaviour over previous samples. This behaviour can be attributed to the expected nonlinear conductivity relationship with a ~11;11;11111~11 threshold carbon fibre pe~c;ellLdge ~;ol~re~llldlion delllon~
20 that the phase shift response is far more sensitive to this threshold than the amplitude response. In the case of the amplitude l~ollse, its ;I~ ;vily to the threshold is also mnd~Pr~ted by the ~ cc,llllil,ulion from the slight coaxial fibre ~ nmPnt The near i-lPntir~l lG~ollses of tube S~rnrllos E & F indicate that the choice of resin system has a negligible collllil.ulion to the c--n~ rtivity response.

25 Tube Sample G, with the pe~ ldge of carbon fibre reduced to 25 % d~lllo~ aled an ~ttenl-~tion l~pol~e of 0.7651 and had no effect on phase shift.

CA 02237432 1998-0~-12 Co.,~o~6le Tube/End-fit~ings Junctions In addition to the physical and electr~-m~gnPtir l~ru~e.Lies of the composite tube, the cu~ osile tube must be readily integrated within an existing drillstring. Accordingly, the design incorporates a junction with end-fittings for hlLe~lalion of the composite tube to an 5 existing drillstring as shown in Figures 5, 6, and 7.

Figure 5 is an assembly drawing of the colll~o~ile tube and end-fittings in acco-dal ce with the invention sl~whlg the basic cu~ iL~ tube 12 assembled with the end-fittings 14. Outer wrapping 16 is shown c~ the basic culll~osiLe tube 12 with the end-fittings 14.
Figure 6 is a cross-section~l drawing of an end-fitting showing details of the end-fittings.
10 Figures 6A and 6B show details of the cross-sections of the end-fittings at lines 6A-6A and 6B-6B respectively. Figure 6C shows the preferred dimensions of the end-fittings for integration with a drillstring. Figure 7 is a drawing of an ~ltprn~te embodiment of the assembled composite tube/end-fitting.

As for the design of the basic composite tube, the critical design issues for the end-fittings 15 include bûdy ~lirr~P~ and strength in ~Miti()n to load transfer between the composite body section and end-fittings.

In accolJance with the invention, the junction is ~IP~ign~1 to provide sep~r~tp load paths for the axial cu.l.~ ion and tensile loads from the cc....~osiL~; sub body to the end-fittings in order to avoid relying on a bonded joint to carry loads for the life of the fitting. The 20 cc,.."ule~:~ion load is carried from the basic Cu..-~osiL~ tube 12 directly against bearing surfaces 20, the axial tensile loads are carried against axial tension surfaces 22, the torsional forces are carried against the torsional transfer surfaces 24 and the bending stress forces are carried against the bending stress transfer surface 26.

The bending stress transfer surface 26 provides a section over which the bending load 25 tl~lsr.,.~ from the end fitting 14 to the composite tube 16. This surface is required to prevent rotational bending fatigue from occllrring in the end fitting 14. p~nt~tion~l bending fatigue is a major cause of failure in downhole tools. The bending stress transfer surface has a m~imllm ~ of 6.00 inches to ..,~ the strength required in the coll~osiL~
tube. This .l;~..,..el is made as large as possible to ..,i~ the bending stress at the~0 shoulder 28. It has been shown that in order to prevent fatigue cr~rking, the ...illi........
of a reduced section of a drill sub is such that its ..,~ of inertia (I) is no less than 29.5% of that ~ lclll~t~d using the nominal O.D. of the drill sub. In this case, this ,..i"i,..."" ,1i,....~ is S inches. The 4.25 inch ~li,...lrl~. shown is less than this 5 inch CA 02237432 l998-05-l2 W O 97/21117 PCT/CA9~/00768 27 .,.i.~i.. ,. and conceq~lPntly this section of the end fitting cannot carry the full bending load.
Accordingly, the bending stress transfer surface 26 is tapered at 2 inches per foot to allow the bending load to be L~ relled from the end fitting 14 to the cull~osiLe tube 16 prior to the 4.25 inch ~ mf~trr ~ 5 The torsional transfer surfaces 24 provide a balance between the torsional capacity of the end fittings 14 and the co~ osiLc tube 16, thus ...~x;...;,.;.~g the overall tcr.cic-n~l capacity of the assembly 10. The 4.25 inch ~ lel is the .. i.. i............ .needed to meet the torsional le~uilc,.ll~llLs for the end fittings 14. Using this ~ m~otf~r results in the ~n~x;........
area available for the torsional transfer surfaces 24.

10 The axial tension surfaces are also provided with tapered surfaces 22.

It is ~.~,r~"cd that the end fittings 14 be ...~....r;~ d from non-m~gnrtic material to f::~r.ilit~te MWD tools. However, they may be l~ ri~r~ cd from AISI 4145H MOD ifm~gnf fir properties are not a concern.

Junctzon Theo~y and Design 15 As in~lir.~tr(l~ the metal/composite junction is ~1eci~nPd to transfer torsion, axial col~ ,ssion, tensile and bending loads. The design and analysis of the end-fitting conc~ ?red the following:

1. ~-.;--;--...--- thir~npss of metal required to carry load;
2. ;~f - r; re ples~ul~ for coll~ sil~ on the tapered section of the fitting; and, 20 3. kick-out load created by the tapered metal fitting.

Using an oct~h~ lr~l shf a.hlg stress crit.orinn the .,.i.,i.. ", ~ , of the end-fitting was ~el~- .. i.. Pd with the ~ I;rtn that no yielding is p~.. ill~d under the .. ~xi.. loading vilul~ . The .. ,i..;.. ~ factor of safety used in the analysis was 1.0 as stresses are c~ nl~t~od for impact cllvhul~ L and .~.~xi.... ~ axial and torsion load are ~c.$-lml~d to 25 occur at the same time.

Octahedral Shearing Stress, Y

Y = ~ +37~) r~o~ ng condition: 800,000 lb. axial and 600,000 Ib.-in torque Dim~n~ion~ Outside ~ el = 4.25 inches, Inside .l;;....~(~. = 2.25 inches ~J = axial stress = load/area = 800,000/10.2 = 78,350 psi 5 ~ = shear stress = T(OD/2J) = 600,000(4.25)/2(29.5) = 43,200 pSi y = ~(78,3502 + (3)43,2002) = 108,300 psi Y}eld Strength (..,;..;...l....) = 110,000 psi Factor of Safety = 110,000/108,300 = 1.01 The design of the tapered section of the fitting was based on the concept described in "The 10 NCF (No Cut Fibre) Coupling", W. Rurnberger, B. Spencer, Presented at the ~m~riç~n Helicopter Society Meeting On Composites, June, 1985, Stamford, C~ .rç~

Figure 8 shows how the torsion load is reacted by the polygon shape on the end-fitting. A
similar free body is used for the axial load except that the loading on the polygon surfaces is co~t~nt not tri~n~ r, and both traps are used to react the axial tensile load.

15 T = (d,uP+PL)F, where T = Applied torque = 600,000 Ib.-in.
~4 = Coeffi-~ient of Friction = .2 d = 2.367 inches (average) L = .327 inches (average) 20 F = number of flats = 8 Solving for P

P = 93,710 pounds W O 971211~7 PCT/CA96/00768 Using the force normal to the fitting tapered polygon section the coll~osiL~ bearing stress aBT due to the torsion load can be calculated.

area of flat = 5.76 in2 aBT = 93,710/5.76 S aBT = 16.270 psi The bearing stress created by the tensile load on the drill sub is c~lc~ t~d next and added to the stresses ~1Pte-min~d above for the torsion load.

This analysis inr.l~ldes the additional area of the conical taper in the inboard trap. This trap was not inrlll<l~l in the c~lc~ ti-~n for reacting the torsion load because it is not a polygon.
10 Using a similar free body ~ r~m as pll,s~ ed previously the bearing load on the flats and conical taper can be c~lcnl~t~d for the 800,000 pound axial load as shown below.
aBA = load/area area of flats = (8) 5.76 in2 = 46.08 in2 area of conical taper = 28.83 in2 lS total area = 74.91 normal load = 800,000/sinl5 pounds aB~ = 800,000/(sinl5)(74.91) ~ = 41.26~ psi The total bearing stress on the tapered sections of the fitting are;

21) Tapered polygon bearing stress = 16,270 ~ 41,260 = 57.530 psi Conical inside taper bearing stress = 41~260 psi The ultimate bearing strength is 60 ksi. Since the c~lrll1~t~d bearing stress is created by an impact load the margin is considered ~ t~ even taking into account possible uneven load share between the two tapered sections.

25 Next, using the normal load the kick out load can be ç~lrll1~ted for both the axial and torsion loads cc,lllbilled.

Total kick out load, KL

KL = F*Pcosl5 + Tensile Load/tanlS = 8(93,710)cosl5 ~ 800,000/tanl5 Kl = 3.710~000 pounds Using an allowable tensile stress of 525 ksi (.75x700 ksi) for the carbon fibre, the required 5 area of hoop fibre to react the kick out load can be c~ fpd as follows.

area = 3,710,000/525,000 area = 7.07 in2 The fitting is ~Psi~nPd to allow for adequate hoop fibre.

To illl~love load transfer and reduce stress conc~ laiions, the hoop fibre is interspersed 10 with the helical wound fibre.

The }ast load condition to conci~ler is the culll~les;,i~e load. When only con~idering the area of con~osile a~j~r~nt to the end of the metal fitting to transfer the colll~les~ load, the resulting bearing stress can be c~ t.~d as presented below:

aB--load/area= 300,000(7r/4*(5.25~-2.502)) 15 a~ = 17.900 psi As stated above the ultimate is 60 ksi.

The stress analysis shows tha~ the drill sub is properly rlPcipnPd for all loading conditions.

Manufacture of t*e Composite Tube wit* ~ntegral End-fifflngs M~mlf~l~hlre of the assembly 10 is achieved in accvldd-lce with the following general 20 methodology. It is understood that within the context of the invention, various fibre types, fibre orientation and binders may be employed for the particulars of a design.

Following construction and cutting to length of the basic inner tube 12, CA 0223743: 1998-05-12 1. A metal rod is placed within the basic composite tube and end-fittings 14 are placed over the metal rod. Flange 29 is inserted within each end of the basic co~ o~ile tube 12.

2. End plates are ~rhP~ to the metal rod to lock the basic ccrlll~Josilt: tube 12 and end-fittings 14 together for p!~re...r..~ on a fil~mPnt winder;

5 3. The outer surface of the composite tube 12 and the axial tension 22, torsional transfer 24 and bending stress transfer surfaces 26 of the end-fittings 14 are filament wound with resin hlll,le~;llaLed fibre with a collll~h~lion of helical and hoop wound fibre to an outside rl corresponding to that of the outside ~ , of the end-fittings 14.

Other Design Considerations 10 During fil~mPnt winding or following completion of the fil~m~nt winding, an abrasion l~si~ll coating rnay be blended within the binder or added after curing of the assembly on the outer surfaces of the composite tube. The ~l~.~ion lesi;,l~lL coating is ~I~,rc;l~bly a wear-~esi~ trowelable coating such as ArmorStone~ CeraTrowel from DuraWear Colrporation.

A stabilizer/wear pad 30 may be used either on the end-fittings 14 or on the colll~o~iLe body 15 16 in order to ll~ill;l..;~f. the wear to the cu~ JG;~ m~t~ri~l. The stabilizer/wear pad 30 may also include additional sensing elpmpnt~ such as rutile focussing lenses 32 as shown in Figure 7 for use with micro-pulse imaging radar c~ . Stabilizers 30 may be integral or l~"l-uvable from the assembly 10. Figure 7 also shows a logging tool 40 within the bore of the assembly 10. FY:3mplPs of typical sensing e4uip.l~llL such as a neutron source and 20 detector 42, gamma ray detector 44, le~is~iviLy Colll~o~ 46 and acoustic ranging e~ l 48 are also shown. The ends of the assembly 10 are shown with le,~eclive threaded surfaces 50 and 52 for i..l~.,.l;on of the end-fittings 14 with a ~lrill~trin~.

Fullhellllore, a resin inrlllflin~ an amount of ceram c powder blended into the resin is cu--l~.--l-lated to e~lhdllcc the wear properties of the culll~o~ile m~t~ri~l 25 Sealing of Metal/Composite Jrmetion Sea1ing of the metal/composite junction can also be implPmPntPJl on a number of the junction surfaces using glues, gaskets and/or o-rings without ~f~cting the function of the surfaces.

An example of a sealing system lltili7ing an o-ring is shown in Figure 9. In this embodiment, the end fittings are in two components, an inner fitting 14a and an outer fitting 14b joined by threads 14c. The basic composite tube 12 and outer ~rvld~u~ g cull~po~ e layers 16 are assembled as described above on the inner fitting 14a. At the junction between 5 the inner and outer fittings 14a and 14b, an o-ring 14d is provided which may be eulllylessed by ti~l,l~...i.~g outer fitting 14b against inner fitting 14a.

A further method of sealing the inner surfaces of the cc,lll~,o~ e tube and junction may be utilized in which a solution of sodium silicate is pre~,~,uli~cd within the assembly after curing of the fibre layers such that the sodium silicate is sqnPP7~Pd into any cracks or voids 10 in the composite tube or at the junction and llle.edr~cl subjected to a secu,lldc,l y curing.

Still further, sealing could be achieved using a ~"lwvdble tube running through the bore of the composite tube and metal end-fittings. In the case of the tube being a composite tube, the tube could run the entire length of the C ,lll~,OSi~i; tube and end-fittings. This inner composite tube would be provided with seals on its outer rl;s....f~ at both ends for sealing 15 the inner tube with respect to the outer composite tube and end-fittings and, hence, the c~ o~,ile/end-fltting junction.

Alternatively, metal sleeves could also be utilized to effect sealing of the colll~osiLe/metal j.mrtic,n In this case, two separate sleeves would be utilized at both ends of the colll~,o~ e/end-fitting sLlu~lulc ~7v~,~ld~u~7illg with ~e end-fitting and a short section of the 20 inner composite tube so as to ".~i"~ , the COlll~Obi~ section in the middle of the tube.
Appl~liale seals would be provided on each end of the sleeve to seal the composite/metal junr.tinn Pre~ ;.l,.g of Metal/~ osite Junction Ful~ll~mole, pre-sll.,ssi,lg the composite/end-fitting junction may be impl~ .led in order 25 to reduce the risk of nlov~ of the composite m~tPri~l with respect to the end-fitting while under load. Several methods for the imp~ m of pre-stress can be utilized.

For example, after the inner composite tube has been assembled onto the metal end-fittings, this assembly can be 1U~ A11Y cc,lll~lessed prior to and during the wrapping of the outer fibre layers. This can be achieved by colllplessillg the end-fittings and basic 30 conl~o~i~e tube whilst these CU111~JOIIC1Il~ are on the assembly rod and by ~ g the a~,op.ia~e Cu~ eSSiv~; force during Wl~,u~illg and curing of the outer layers. After curing, the c.,~ ,cDsive load is released thereby ill~alLhlg a tensile load in the outer tube and, thus, a colll~,es~ive load on the taper traps on the metal end-fittings.

AlLGIl~lively, or con~;ullGIllly, the cotoffi~i~nt of thermal eYpânci~ n of the composite tube can be made less than that of the steel end-fitting. In this situation, during curing and S sllhseq-~ent cooling, the culll~o~ile tube would shrink faster than the metal end-fitting.
Accordingly, if the curing Ic~ aLulG is above the o~c~aling ten~Glal~ ûf the drill collar, the cc,l.l~o~ile would exert a collll!lessive (radial) load on the metal end-fitting.

Still further, the gec""tlly of the end-fltting could be adapted such that a lock nut system is impl~m~nted to impart a CUIll~ ivc load on the taper traps of the end-fittings. This can be 10 achieved using systems as shown in Figures 9 and 9A wherein the end-fittings are in two sections with an inner 14a and outer 14b end fitting. As shown, a colll~ ion surface 14e is provided on t_e outer end fitting 14b which can be tightPnPd against the outer fibre layers 16 after curing thereby illl~a~ g a Co"""~ivG load on the taper traps of the metal end-fittings.

15 AI~G,Il~LivGly, the geolllcl,~y of the end-fitting could be adapted such that a lock-nut is used to impart a cul~ e;,~ive load on the taper traps of the end-fitting as shown in Figure 10. A
nut 14f is threaded on a t_readed section 14c ûf the metal end-fitting 14. As is shown, the nut 14f has a colll~lc~ion surface 14e which can be tight~n~od against the outer fibre layers 16 after curing thereby hll~alli~ aculll~lc:~sivc load on the taper traps of the metal end-20 fittings.

A further example of a method of pre-:,L,~,ssil,g the joint is shown in Figure 11 wherein the end fittings are also provided as two sections as an inner 14a and outer 14b end-fi~ting. In this embodirnent, a threaded section 14c is provided on both the inner and outer end-fittings. The outer section is provided with a geolllGIly such that the bending stress transfer 2S surface 26 is hlcol~olà~ed on the outer end-fitting. As shown, the outer end fitting may be tight~n~d against the inner fitting. Thus, after wlà~l~ing the outer fibre layers around the inner and outer end-fittings, the outer end-fitting may be tight~n~d against the inner end-fitting thereby hll~alLillg a cc Ill~lcssi~e and radial load on the junction.

Static ~esting Data for C~".l,osile Tube wit* End-F~tings 30 Static testing of a 25 foot culll~o~ drilling sub with a 6.75 inch OD and end-fittings was completed as follows:

a) Axial Load Test~ng An axial loading cycling test was used to evaluate the co~ o~ile tube behaviour during cyclic tension and cu~ lession loading.

Tensile/c~ ssivc testing was conducted in a servo-hydraulically controlled 3.5 rnillion S pound Tubular Testing System (TTS). Purpose specific test fixtures were m~mlf~l~tllred to connect the specimen ends to the TTS actuator and cross-head. Applied load was lllea~u.ed via the TTS dirr~lellLial pressure tr~ncfillrer (serial number 135841) for the 1500 kN load range used for this test. The differential prcs~ulc tr~n~ducer had an error range of -0.135%
full-scale in co~ cssion to +0.151% full-scale in tension.

10 Disp!~m~nt was ~--ea~.l-cd directly from the TTS actuator Linear Variable Dirrc~c~llial Tldl~rc,ll-~. (LVDT). TheLVDT (serial number 91203) had a ~:0.5%% (~t0 010 inch)full-scale error for the ~50 mm range used for this test. Applied load, actuatordispl~ , and time were mo~ ilu~,d continuously during testing and recorded to disk via a digital data a~qlli~ition system.

15 Tensile/Cc~ essi~e tests in~ fled Axial tension to 300 kips;
Axial tension cycling between 0 and 200 kips for 10 cycles;
Axial co..l~.cssion to 75 kips;
Axial colll~.ession cycling between 0 and 50 kips for 10 cycles;
20 One hour creep test at 310 kips;

b) Tor~:a o~ Testing Torsional testing was c~-n~ ctecl in clockwise (make-up) and counter-clockwise (brèak) directions to verify torsional Ca~acily~

Testing was con~ ted using lol~lui~lg ~ capable of torques of 160,000 ft-lbs make-25 up and 200,000 ft-lbs break. A reaction torque meter capable of 100,000 ft-lbs make-up/break was also in~t~ l on the end of the sub to monitor the applied torque.

Torsional testing col~isLcd of static torque up to 50,000 ft-lbs. make-up in 5,000 ft-lbs hlcn,~llclll~ followed by a static torque to ~5,000 ft-lbs break in 5,000 ft-lbs hlclclll.,~

Wo 97/21117 PCT/CA96/00768 Ad~litinn~l testing in~ PA cycling make-up torque at 20,000-25,000 ft-lbs followed by cycling break torque at 20,000-25,000 ft-lbs for 10 cycles each. Static torque to 50,000 ft-lbs make-up and 45,000 ft-lbs break was applied again after cyclic testing to verify torsional ~ hlle~lily.

S Composite Drill Sub with Loggzng Sub Transparency Tests The composite drill sub was sl~rcPc~fillly tested at a downhole training service facility in an ellvilo~ Glll typical to those of a drilling rig in a field setting. The cu~ osil~ drill sub was subjected to typical downhole con-liti~-n~ as well as being sul)je~ d to a logging run in which the ~ n~ed l~ y and propagation properties of the drill sub were compared I0 with those of an all-steel logging sub.

The testing involved assembling a composite drill sub into the bottom hole assembly of a drillstring at the surface and tripping the ~1rill.~tring back into the wellbore to a depth of 650 metres. The presence of the Co.,.~osiLG drill sub in the drilling sub did not affect normal rig operations of 1) tripping in, 2)1oL;~Iillg the table, 3) power tonging drill pipe together, 4) 15 ~.h~ining drill pipe apart or 5) circulating fluid in the wellbore.

At the 650 metre depth, a c~"..pe .~e~l neutron-gamma ray tool was lowered into the Cc~ osiLG drill sub and a logging run to the surface initi~tP-1 The results of the logging run in co~ ;col) with an all steel drill sub in-1iç~t~

1. il-l~luv,ed gamma ray s~ iLiviLy. The 2.5" thick cw~.~o~iLe wall section introduces 20 minim~l gamma ray -~lr-~ oll- In cUIll~aLi;~Oll~ a 0.8" thick steel wall ~ le~ gam~na ray propagation up to 60%. A 2.5" thick steel wall is e-~cPnti~lly opa~ue to gamma ray propagation llleasu~,llG~

2. iln~L. vGd neutron s~.~iLiviLy. The composite drill sub has lower ~ ;on properties cun~ared to steel. Neutron pOlOSi~y llle~i~Ul~,~llGl1~7 improve from within a composite drill 25 sub as the Cu~ osilG fibre physically displaces wellbore fluid thereby ...;..;.,.;,;..g the neutron moderating effect of wellbore fluid.

3. i.ll~luvGd electrom~gnPtir propag~ti--n The ~lll~osiLe drill sub has a higherelectrf~m~gnPtir L~ pa~ ;y colll~ed to steel. Furthermore, as in result 2) above, ele~ u...~gnPtir propagation is aided as well by the physical displ~ ..l of the wellbore 30 fluid.

W O 97~1117 PCT/CA96/00768 A colll~a~ison of a gamma ray log between conventional wire-line logging and a logging while tripping log is shown in Figure 12. As can be seen from this Figure, the gamma ray log is well collela~ed between the two l"ea~ .,ment techniques.

As a result of the reduced attenll~tion properties and ~.~h~ ed pr~agdlion prope.~ies of the 5 cc.lll~,o~iLe drill sub, the overall logging speed can be h~cl~ased and the operating time thereby reduced, inflir~ting a fim~m~nt~ lovt;mcllL in the use of a composite drill sub for logging as c~ afed to an all-steel design.

The terrns and expressions which have been employed in this .specifi~tion are used as terms of description and not of limh~ti~ns~ and there is no intention in the use of such terrns and 10 e~ ,ssiolls to exclude any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the claims.

Claims (48)

Claims

1. A composite body having signal attenuation properties for a physical and performance design point, the composite body comprising a plurality of fibre layers impregnated with a binder, wherein the composite body has a longitudinal axis and the fibre layers include a first layer type and a second layer type, the first layer type including carbon fibre generally oriented with the longitudinal axis to minimize signal attenuation and wherein each fibre layer is selected in accordance with desired mechanical, signal attenuation and phase shift properties of the design point.

2. A composite body as in claim 1 wherein said body is formed as a composite tube adapted for use in a drill string wherein the first layer type is a plurality of layers interspersed by layers of the second type.

3. A composite body as in claim 2 wherein the composite tube is adapted for receiving a logging tool.

4. A composite body as in any one of claims 1-3 wherein the fibre layers include any one of or a combination of fibreglass and aramid fibres.

5. A composite body as in any one of claims 2-4 wherein the carbon fibre is oriented at ~ 10°
with respect to the longitudinal axis of the composite tube.

6. A composite body as in any one of claims 1-5 wherein the carbon fibre is a high modulus carbon fibre.

7. A composite body as in any one of claims 1-6 wherein the fibre layers include any one of or a combination of a fibreglass fibre comprising (1) 52-56 wt% silicon dioxide (silica), 16-25 wt% calcium oxide, 12-16 wt% aluminum oxide, 5-10 wt% boron oxide, 0-5 wt% magnesium oxide, 0-2 wt% sodium, potassium oxides, 0-0.8 wt% titanium oxide, 0.05-0.4 wt% iron oxide and 0-1.0 wt% fluorine, or (2) 65 wt% silicon oxide (silica), 25 wt% aluminum oxide and 10 wt% magnesium oxide or alumina-boria-silica ceramic fibres.

8. A composite body as in any one of claims 1-7 wherein the aramid fibre is a high strength aramid fibre.

9. A composite body as in any one of claims 1-8 wherein the binder is an epoxy resin.

10. A composite body as in claim 9 wherein the epoxy resin is a selected from any one of a cyanate ester resin or a bisphenol F epoxy resin.

11. A composite body as in any one claims 1-8 wherein the binder is cement based and is selected from any of one of or a combination of portland cement, portland-aluminous-gypsum cement, gypsum cement, aluminous-phosphate cement, portland-sulfoaluminate cement, calcium silicate-monosulfoaluminate cement, glass ionomer cement, or other inorganic cement.

12. A composite body as in any one of claims 2-11 wherein the first layer type is wound at 10° with respect to the longitudinal axis of the tube, the first layer type comprising 25-50%
high modulus carbon fibre, 0-44% aramid fibre and 16-50% high strength fibreglass.

13. A composite body as in any one of claims 2-12 wherein the second layer type is wound at 90° with respect to the longitudinal axis of the tube, the second type comprising 100% high strength fibreglass.

14. A composite body as in any one of claims 2-13 wherein the first layer type constitutes 90%
of the total wall thickness of the tube.

15. A composite body as in any one of claims 2-14 wherein the second layer type is equally interspersed through the composite tube at 1-9 discrete radial positions.

16. A composite body as in any one of claims 2-15 wherein the first layer type is wound at 10° with respect to the longitudinal axis of the composite tube, the first layer type comprising 25% high modulus carbon fibre, 25% aramid fibre and 50% high strength fibreglass.

17. A composite body as in any one of claims 2-16 wherein the composite tube has a signal attenuation response of at least 70% at 20kHz.

18. A composite body as in any one of claims 2-17 wherein the composite tube hasmicrostructure with a fibre volume fraction of 60%.

19. A composite body as in any one of claims 7-18 wherein the composite tube has performance standards including tensile load, compressive load, torsional load, internal pressure, endurance limit, lateral stiffness, impact strength, tensile strength, and yield strength which meet or exceed the standards of the American Petroleum Institute Specification 7.

20. A composite body as in any one claims 1-19 further comprising an abrasion resistant coating on the outer surface of the composite body.

21. A composite body as in claim 20 wherein the abrasion resistant coating is a ceramic powder filled epoxy.

22. A composite body as in any one of claims 2-21 further comprising end-fittings integrally attached to the composite tube by additional fibre layers and binder.

23. A composite body as in claim 22 wherein the end-fittings include:
a tube seat for seating the end-fitting within the composite tube;

at least one compression bearing surface for supporting a compression load between the end-fittings and the composite tube;

at least one torsional transfer surface for transferring torsional load between the end-fittings and the composite tube;

at least one bending stress transfer surface for supporting a bending stress load between the end-fittings and composite tube;

at least one axial tension surface for supporting an axial tension load between the end-fittings and composite tube.

24. A composite body as in claim 23 wherein the at least one torsional transfer surface comprises multiple surfaces.

25. A composite body as in any one of claims 23-24 wherein the at least one torsional transfer surface comprises eight surfaces.

26. A composite body as in claim 25 wherein each of the eight surfaces are parallel to the longitudinal axis of the end-fittings.

27. A composite body as in claim 25 wherein each of the eight surfaces are tapered with respect to the longitudinal axis of the end-fittings.

28. A composite body as in any one of claims 24-27 wherein the multiple surfaces are a combination of both tapered and parallel surfaces with respect to the longitudinal axis of the end-fittings.

29. A composite body as in any one of claims 22-28 wherein the additional winding is high modulus glass fibre wound at 90° with respect to the longitudinal axis of the end-fittings.

30. A composite body as in any one of claims 22-29 wherein the end-fittings further comprise stabilizers.

31. A composite body as in claim 30 wherein the stabilizers include rutile or zirconium focussing lenses for use with micro pulse imaging radar.

32. A composite body having a composite tube middle section and integral end-fittings, the composite tube middle section having a signal transparency, the composite tube middle section characterized by:

a basic composite tube, the basic composite tube including a plurality of binder-impregnated fibre layers of a first and second type wherein the first type layers are interspersed by layers of the second type and the first layers are wound at ~ 10° with respect to the longitudinal axis of the tube, the first layer type comprising 40% high modulus carbon fibre, 44% aramid fibre and 16% high strength fibreglass and the first layer constitutes 90% of the total wall thickness of the tube and wherein the second layer type is wound at 90° with respect to the longitudinal axis of the tube, the second type comprising 100% high strength fibreglass equally interspersed through the tube wall at a plurality of discrete radial positions;

the end-fittings characterized by:

a tube seat for seating the end-fitting within the basic composite tube;

at least one compression bearing surface for supporting a compression load between the end-fittings and the basic composite tube;

at least one torsional transfer surface for transferring torsional load between the end-fittings and the composite basic tube;

at least one bending stress transfer surface for supporting a bending stress load between the end-fittings and basic composite tube;

at least one axial tension surface for supporting an axial tension load between the end-fittings and basic composite tube.

33. A composite body as in any one of claims 2-32 wherein the composite tube is adapted for data acquisition from a wellbore, the composite tube having a signal transparency allowing the use of data acquisition equipment from within the tube, the data acquisition equipment selected from any one of or a combination of gamma ray emitters and sensors, neutron emitters and sensors, acoustic emitters and receivers, inductive EM emitters and receivers, and directional sensing equipment.

34. An end-fitting for configuration to a composite tube comprising:

a tube seat for seating the end-fitting within the composite tube;

at least one compression bearing surface for supporting a compression load between the end-fittings and the composite tube;

at least one torsional transfer surface for transferring torsional load between the end-fittings and the composite tube;

at least one bending stress transfer surface for supporting a bending stress load between the end-fittings and composite tube;

at least one axial tension surface for supporting an axial tension load between the end-fittings and composite tube.

35. An end-fitting as in claim 34 wherein the at least one torsional transfer surface comprises multiple surfaces.

36. An end-fitting as in any one claims 34-35 wherein the at least one torsional transfer surface comprises eight surfaces.

37. An end-fitting as in claim 36 wherein each of the eight surfaces are parallel to the longitudinal axis of the end-fittings.

38. An end-fitting as in claim 36 wherein each of the eight surfaces are tapered with respect to the longitudinal axis of the end-fittings.

39. An end-fitting as in claim 35 wherein the multiple surfaces are a combination of both tapered and parallel surfaces with respect to the longitudinal axis of the end-fittings.

40. A composite body as in any one of claims 22-33 wherein the end-fittings and outer layers define a composite/end-fitting junction and the end-fittings are adapted to receive a lock nut for imparting a compressive force on the composite/end-fitting junction.

41. A composite body as in any one of claims 22-33 wherein the end-fittings include an inner and outer end-fitting adapted to impart a compressive force on the composite/end-fitting junction.

42. A composite body as in any one of claims 22-33 wherein the end-fittings and composite layers define an inner composite/end-fitting junction, the composite tube further comprising an inner sleeve adapted to seal the inner composite/end-fitting junction.

43. A composite body as in claim 42 wherein the inner sleeve is a metal or a composite material.

44. A method of forming a composite body, the composite body including a composite tube with integral end-fittings comprising the steps of:
a) winding, a basic inner tube from a binder-saturated fibre on a steel mandrel;b)curing the binder to form a cured tube;
c) removing the mandrel from the cured tube;
d) cutting the cured tube to length to form a basic tube;
e) inserting an alignment mandrel within the basic tube and seating end-fittings within the basic tube over the alignment mandrel;
f) winding outer layers of binder-saturated fibre over the basic tube and end-fittings to form a composite tube with end-fittings.

45. A method as in claim 44 further comprising the step of applying an adhesive coating to the outer surface of the composite tube.

46. A method as in any one of claims 44-45 wherein the end-fittings and outer layers define a composite/end-fitting junction, the method further comprising the step of pre-stressing the composite/end-fitting junction.

47. A method as in claim 46 where pre-stressing the composite/end-fitting junction includes compressing the cured tube and end-fittings during wrapping and curing of the outer fibre layers.

48. A method as in any one of claims 44-47 wherein the coefficient of thermal expansion of the composite tube is less than the coefficient of thermal expansion of the end-fittings and wherein during wrapping and curing of the outer fibre layers a compressive force is induced on the end-fitting.