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PETE 411Well Drilling

Lesson 37Coiled Tubing

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Coiled Tubing

What is Coiled Tubing?

Uses of Coiled Tubing

Properties of Coiled Tubing

Drilling with Coiled Tubing

Buckling

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Buckling of Coiled Tubing

Buckling Modes Sinusoidal and Helical Buckling Buckling in Horizontal or Inclined Sections Buckling in Vertical Section Buckling in Curved Wellbores Prediction of Buckling Loads “Lockup” of Tubulars

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Truck-Mounted Coiled Tubing Reel Assembly

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Coiled Tubing Reel Assembly

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Hydraulic Coiled Tubing Unit

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Cut-away view of the

Injector Head Drive

Assembly

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Some Applications of Coiled Tubing

• Cementing• Plug Cementing (e.g. P&A)• Squeeze Cementing

• Logging• Drilling• Producing• Fishing• Scale Removal

Ref: SPE Reprint Series NO. 38 “Coiled Tubing Technology”

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Sidetrack Procedure

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From OGJ

July 8, 2002p.62

Coil Tubing

Drilling on the North

Slope

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Coil Tubing Drilling on the North Slope

Drilling Rates routinely in excess of 250 ft/hr - drilling in sandstone

Laterals longer than 2,500 ft

Good incremental oil production

Used electrical umbilical for MWD

Used mud motors and 3 ¾-in PDC bits

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No rig required No connections - fast tripping

Fatigue life limit (cycles) Pressure and tension Diameter and ovality

Disadvantages

Advantages

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Reference:

“Coiled Tubing Buckling Implication in Drilling and Completing Horizontal Wells” by Jiang Wu and H.C. Juvkam-Wold, SPE

Drilling and Completion, March, 1995.

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Sinusoidal Buckling in a Horizontal Wellbore

When the axial compressive load along the coiled tubing reaches the following sinusoidal buckling load Fcr, the intial (sinusoidal or critical) buckling of the coiled tube will occur in the horizontal wellbore.

502 .ecr )r/WIE(F

r

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Consider:

(steel) psi 000,000,30 E

ftlb2225.0

ftlb67.2

45.656.8107.3 W

ftlb07.3

23145.65*12)688.12(

4W

mud gal# 8.6 ID; 1.688" ,OD "2

e

22

in*

502 .ecr )r/WIE(F

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lbf 317.39375.0

2225.0*3869.0*10*302F Then,

in 9375.02

2875.32

ODD r

in 3869.0)688.12(64

)IDOD(64

I

5.06

cr

HOLE

44444

Consider:

,

=

rWIEF e

cr 2

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Sinusoidal Buckling Load

A more general Sinusoidal Buckling Load equation for highly inclined wellbores (including the horizontal wellbore) is:

rsinEIWF e

cr

2

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Sinusoidal Buckling Load

For the same 2” OD coiled tubing, at = 45o

506

9375045222503869010302

.o

cr .sin.*.**F

Fcr = 2,789 lbf

rsinEIWF e

cr

2

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Helical Buckling in a Horizontal Wellbore

When the axial compressive load reaches the following helical buckling load Fhel in the horizontal wellbore, the helical buckling of coiled tubing then occurs:

rWIEF e

hel 1222

93750

2225038690103012226

..*.**Fhel

Fhel = 6,065 lbf

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General Equation

A more general helical buckling load equation for highly inclined wellbores (including the horizontal wellbore) is:

rsinEIWF e

hel

1222

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Buckling in Vertical Wellbores:

In a vertical wellbore, the buckling of coiled tubing will occur if the coiled tubing becomes axially compressed and the axial compressive load exceeds the buckling load in the vertical section.

This could happen when we “slack-off” weight at the surface to apply bit weight for drilling and pushing the coiled tubing through the build section and into the horizontal section.

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Buckling in Vertical Wellbores:

Lubinski derived in the 1950’s the following buckling load equation for the initial buckling of tubulars in vertical wellbores:

lbf 161F

)2225.0*3869.0*10*30(94.1F

)EIW(94.1F

b,cr

3/126b,cr

3/12eb,cr

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Buckling in Vertical Wellbores:

Another intitial buckling load equation for tubulars in vertical wellbores was also derived recently through an energy analysis:

1) (Table lbf 212F Alternate

)2225.0*3869.0*10*30(55.2F

)EIW(55.2F

bcr,

3/126b,cr

3/12eb,cr

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Helical Buckling in Vertical Wellbores:

A helical buckling load for weighty tubulars in vertical wellbores was also derived recently through an energy analysis to predict the occurrence of the helical buckling:

lbf 461

)EIW(55.5F 3/12eb,hel

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Helical Buckling in Vertical Wellbores:

This helical buckling load predicts the first occurrence of helical buckling of the weighty tubulars in the vertical wellbore. The first occurrence of helical buckling in the vertical wellbore will be a one-pitch helical buckle at the bottom portion of the tubular.

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Helical Buckling in Vertical Wellbores:

The upper portion of the tubular in the vertical wellbore will be in tension and remain straight. When more tubular weight is slacked-off at the surface, and the helical buckling becomes more than one helical pitch, the above helical buckling load equation may be used for the top helical pitch of the helically buckled tubular

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Helical Buckling in Vertical Wellbores:

The top helical buckling load Fhel,t is calculated by simply subtracting the tubular weight of the initial one-pitch of helically buckled pipe from the helical buckling load Fhel,b, which is defined at the bottom of the one-pitch helically buckled tubular:

3/12e

hele3/12

et,hel

)0.14(EIW

LW)EIW(55.5F

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Helical Buckling in Vertical Wellbores:

Where the length of the initial one-pitch of helical buckling or the first order helical buckling is:

(10) )W/EI16(L 3/1e

2hel

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Helical Buckling in Vertical Wellbores:

From Table 1, it is also amazing to find out that the top helical buckling load, Fhel,t, is very close to zero. This indicates that the “neutral point”, which is defined as the place of zero axial load (effective axial load exclusive from the hydrostatic pressure force), could be approximately used to define the top of the helical buckling for these coiled tubings.

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Helical Buckling in Vertical Wellbores:

lbf 12F

)2225.0*3869.0*10*30(14.0

)EIW(14.0F

t,hel

2/126

3/12et,hel

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Buckling of 2” x 1.688” CT

Horizontal

crhel FF 122

rWIEF e

cr 2 = 3,317 lbfSinusoidal:

Helical: = 6,065 lbf

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Buckling of 2” x 1.688” CT

Vertical

Sinusoidal, bottom:

or

lbfWIE.F/

eb,cr 161941312

lbfWIE.F/

eb,cr 212552312

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Buckling of 2” x 1.688” CT

Vertical

Helical, bottom:

Helical, top:

lbfWIE.F/

eb,hel 461555312

lbfWIE.F/

eb,hel 12140312