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OilfieldTechnology
February
2014
Thisarticlesummarises the
newcoiled tubing technologycalled
SMARTaper™beingdeployed in
unconventionaldevelopments,
thecommonstringdesignsbeing
utilised toensuredurability
andextend reach, andhow this
technology iscreatingasafer
environment for coiled tubing
operations toexpand theoperating
envelopeworldwide. Somebenefits
ofusing this technology:
Ì
Ì
SMARTaper can improve safety
by increasing thewall thickness
atbiaswelds located in the
zonewith thehighest amount of
fatigue.
Ì
Ì
Reliabilityand string life
are increased15 ‑ 20%with
additional fatigue lifeof the
coiled tubing technology.
Ì
Ì
The technologycan improve
reach inunconventionalwells
byquickly transitioningbetween
optimalwall thicknesses
tominimisebuckling in the
horizontal sectionbasedonwell
design.
Ì
Ì
Improves reach
inunconventionalwellsby
quickly transitioningbetween
optimalwall thicknesses to
reduce stringweight in the
horizontal section.
Newtechnology
parameters
It has longbeenunderstood that
increasing thewall thicknessof
coiled tubingextends the fatigue
lifeand increases theaxial
capacity. Byvarying thewall
thickness, aconstant factorof
safetyalong the lengthcanbe
employedbasedonoverpull
calculations. Itwould seem
the logical choicewouldbe to
increase the thicknesson the
entire string tomake it asdurable
aspossible.However, thisalso
increasesweight,whichmakes
transportationandcrane lifts
difficult. Furthermore, increasing
thewall thickness can reduce
volumetric flow ratesand
reduce thehorizontal reach in
unconventional developments.
Therefore, acarefully
engineered, tapered string is
required inmost applications.
Inorder tomanufacture these
tapered strings, theprocess
entailswelding flat stripsof
steel together end‑to‑end,which
Figure1.
Standardtaperedstringwith longer
transitionsbetweenwallthicknessesatbottomof
string.
Figure2.
SMARTaperstringwith improvedwall
thicknessatbiaswelds(smallspikesattopof
string-Note ‘C’).Thesearegradualandspan
approximately100mtotalforthetransitionto
accommodateabiasweldandreinforcethe
jointfor improvedfatigueandsafety inthefield.
The lowersectiontransitionsquicklywhichcan
beengineeredtoextendreach inhorizontal
applications,andreducethepropensityto lockup.
Figure3.
SMARTaperstripwherethedistalendsarethickerthanthemajorityofthebasematerial.Biaswelds
jointhethickersectionsofstripstogethertomakeacustom lengthoftube.
Figure4.
SMARTaper intubeformshowingthebiaswelds inthethickermaterial.TheODofthetube is
consistentwhilethe IDchangesgraduallytoeliminateanynozzleeffect,turbulentfloworrestriction.The
additionalthicknessaddsreinforcementtotheweldand increasesthefatigueperformanceofthe joint.
