Coiled Tubing BHA

Coiled Tubing BHAs
What is needed to do the job? What can go wrong? What do you need to get out of trouble? How could you prevent it? Where are the needed tools, talent, equip, fluids, etc, located?
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George E. King Engineering GEKEngineering.com
CT Well Service Usages

Fluid Placement & Cleanout - 70% of use Cement Squeezing Production Logging Cleanout-Norm./Rev. Shift Sliding Sleeves Inflatable Packers Perforating Chemical Stimulation Fraccing Underreaming Junk Milling Fishing Window Milling Plug Setting Drilling Etc. Downhole Camera
George E. King Engineering GEKEngineering.com 2
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Pre Rig-up Issues

Is this the right tool for the job? What are lessons learned from others? Check CT history and model remaining life against operational requirements. Does your BHA and job design leave sufficient alternatives if problem countered? What over-pull remains at bottom of well? Determine operation killers and minimize risks.
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Other Rig-up Notes

Measure all parts of the BHA (O.D.s & I.D.s) CT can collapse (with check valves in place) while pressure testing tubing. Be aware of differential pressures. Rigid extensions needed on CT to bypass GLMs? Any upsets or non-beveled areas on the tools? Hydraulic disconnects compatible with other parts of the BHA? BHA compatible with wellbore restrictions?
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CT to Tool Connectors
Crimp-on (Roll-on Style) Cold Roll (Roll-on Style) Dimpled Style Set-screw Style Internal Slip Style
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External Slip Style Combination - slip and dimpled/setscrews Welded Threaded
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Coiled Tubing Connectors

Coiled tubing Coiled tubing Setscrew Setscrew O-ring O-ring O-ring Crimped tubing
Grapple connector
Dimple connector
Roll-on connector
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g12.tif
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Internal Slip Style Connectors

Strong connection Not effected greatly by wall reduction. Can be difficult to install. Sensitive to CT ovality. Reduction in I.D. Can be difficult to remove.
External Slip Style Connectors

Strong connection Can be effected by wall reduction. Relatively easy to install. Sensitive to CT ovality. Widely used in the industry.
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Other Connection Methods

welding - used for bottom profiles, repair threaded CT - rare, usually weak (thin wall) Suggestion - check every connector with a pull test (and cover the hole!)
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Downhole Tools
circulation needs and effect on tool performance clearances (both small and large) weights functions - mixed vs single well deviation
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Downhole Tools
Connectors Release Tools Centralizers Nozzels Impact Tools Motors Cutters Underreamers Running Tools Retrieving Tools Hydraulic Push/Pull Tools Packers Valves Logs Perf Guns Electric Tools
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Releases
hydraulic and ball drop releases rate sensitive trash sensitive?
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Release Joints
CT release joint Releases CT from toolstring in a
controlled manner Resulting fishing neck on toolstring allows easy reconnection
Release joints available with Tension-activated release Pressure-activated release A combination of the above
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Coiled Tubing Check Valves

Check valves Generally attached to CT connector at end of CT string Prevent flow of well fluids into CT Maintain well security when tubing at surface fails/damaged Should be part of every CT bottomhole assembly
only omitted when the application precludes their use e.g., reverse circulation required
Types of check valve Flapper check valves Ball and seat check valves
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Coiled Tubing Check Valves
Flapper check valve assembly
Ball and seat check valve assembly
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Nozzles and Jetting Subs
Single largediameter port
Muleshoe Angled Jet Nozzle
Multiple smalldiameter ports
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Water jets fan out quickly and lose impact force.
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Nozzles and Jetting Subs

Key features of nozzles and jetting subs Form downhole end of CT bottomhole assembly Generally of simple design and construction Position and size of nozzle ports
determined by required jetting action
These tools fall into two categories

circulating subs jetting subs reversing subs
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Circulating Subs
Nozzles used where fluids circulated without a jetting action Require a large port area Port area may be composed of Several small ports to increase turbulence A few large ports, with little pressure drop across
nozzle
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Jetting Subs
Nozzles used where jetting action required Require a small port area Port area usually composed of several small ports
Efficiency of jetting nozzle dependent on fluid velocity through port Position, shape and direction of jet ports determined by intended application Combination nozzles often used to perform special operations
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Bowspring Centralizer used for centralization of tools in fishing in deviated wells.

Jars
Jars Deliver sudden shock (up or down) to toolstring Generally include a sliding mandrel arrangement
allows brief and sudden acceleration of toolstring above jar
Most jars release in one direction only Some designs can jar up and down without resetting If jar included in CT bottomhole assembly Accelerator must also be fitted
Jars
Types of jars used in CT operations Mechanical Hydraulic Fluid powered (e.g. impact drill) All three jar types operate on the upstroke Only mechanical or fluid powered jars capable of downstroke George E. King Engineering 3/14/2009 GEKEngineering.com
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Overshots
Recommended that only releasable overshots are used in CT operations Principal features of releasable overshots Catch/release mechanism Bowl/grapple assembly Circulation facility
enables circulation of fluid
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Loads and Forces

Tensile Burst Collapse Torsion Cyclic Fatigue Modeling
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Loads
Tensile (last section and in deep well section) Burst (last section and in high pressure section) Collapse Buckling (defered to deviated well section) Torsional (nope, not a typo)
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Tension
Weight produces stretch Increased by BHA weights Increased by friction on POOH Offset to some degree by well fluids
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Uniaxial Tension
F A API y L E 1
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=F/A
B A
E 1
C
0.005
=/L
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Tension failure mode for CT in the laboratory.

Collapse more common than neck down

The collapse failure is more common in the field because of CT ovality and annular pressure reducing collapse resistance.
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Axial Load Capacity

The one-dimensional axial load capacity of the tubing is considered to be the tension load that will produce a stress in the tubing equal to the minimum yield. Ly = SyA where: Ly = CT load cap. at yield, lbs Sy = yield strength of the CT, psi A = x-sect. area of CT, in2
Load Capacity Example

For a 1.5, 0.109 wall CT of 70,000 psi yield strength steel, the one-dimensional load capacity at yield is: Ly = 70,000 psi x 0.476 in2= 33,320 lb an 80% operating factor is common.. Ly = (0.8)*33,320 = 26,656 lb
Operating Safety Factor Suggestions

0.8 under best conditions - new strings, especially high strength strings 0.5 to 0.7 for field welds
0.7 for welds in lower section 0.5 for welds in upper section 0.5 for questionable welds
0.4 to 0.5 for corroded strings

consider refusing the string if corrosion severe refuse string if any evidence of pin holes
Welds
The heating that occurs during the welding process will cause the weld metal and the heat affected zone around the weld to be physically different from the surrounding, original metal. An anode is created by this difference.
An anode can start here or here. Base metal
Heat affected zone
Weld metal (added and different from original base metal)

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Simplistic Depth Limits
Le = Ly(80%)/W where: Le = equivalent string length Ly (80%) = 80% of CT load capacity W = tubing weight (effective), lbs/ft
Depth Limits, without buoyancy
Examples of Depth (length) Limits of 1.5" CT (no buoyancy) CT OD (in) 1.5 1.5 1.5 1.5 1.5 1.5 wall (in) 0.095 0.109 0.134 0.087 0.109 0.134 weight yield 80% yield max string (lb/ft) strength load length in air (psi) (lbs) (ft) 1.426 70,000 23,482 16,466 1.619 70,000 26,672 16,474 1.955 70,000 32,200 16,470 1.313 100,000 30,896 23,531 1.619 100,000 38,104 23,536 1.955 100,000 46,000 23,529
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Other factors that figure in.

POOH loads are increased by:
frictional drag forces along walls frictional drag in fluids bending loads through deviated sections BHA weights
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Weight Indicator Load Verification

WEIGHT INDICATOR READING (lbf)
9000
Measured RIH (model) POOH (model)
4500
500
4,000
8,000
MEASURED DEPTH OF STRING (ft)

Internal Yield Pressure (Burst)

PB = 2 (t wall-min)Sy/OD Where: PB = internal yield or burst pressure, psi t wallmin = thinnest wall, in Sy = yield strength of the CT, psi
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Burst Pressure: This one is really tricky!

Depends on:
CT size CT wall thickness CT strength damage (dents, corrosion, ovality, fatigue) offsetting pressure (its a differential) mechanical loads? - (compression? - usually not a factor)
Theoritical Burst Calc. with Round Tube

CT OD (in) 1.25 1.25 1.25 1.25 1.25 1.25 wall (in) 0.095 0.095 0.075 0.125 0.156 0.151 Yield (psi) 80,000 70,000 70,000 70,000 70,000 80,000 Burst (theory) (psi) 12160 10640 8400 14000 17472 19328
The problem is that the tube isnt round.

Theoritical Burst Calc. with Round Tube

CT OD (in) 1.25 1.5 1.75 2 2.375 2.875 3.5
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wall (in) 0.151 0.151 0.151 0.151 0.151 0.151 0.151
Yield (psi) 70,000 70,000 70,000 70,000 70,000 70,000 70,000
Burst (theory) (psi) 16912 14093 12080 10570 8901 7353 6040
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The Variation of Theoretical Burst in New, Round Pipe and Yield Strength with Tension Load
Burst Press as function of YS

25,000
20,000
Burst Press, psi
15,000
110 ksi 90 ksi
10,000
70 ksi
5,000
0 0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 Tubing Load, psi
When Burst is Affected by Compression

Loads during Snubbing (minor effect!)
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Collapse Pressures
Derated by tension charts are not accurate - tube not round
One of the biggest misrepresentations in the CT data is that of collapse pressure data. Personal Opinion - use these charts as the best possible case and derate the prediction at least 30%.
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g22.tif
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Collapse Curves
They may not be accurate:
Curves do allow deration of CT collapse limits by tension However, no considerations of effect of swell/ovality/damage/corrosion Derate further??? Suggest 30% if you know loads will vary.
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Ovality
Diameter increases most along sides and walls thin proportionally. Ovality creates unequal stress on CT. Some total diameter swell Ovality = (OD max - OD min)/OD spec. Solution? Measurement, Testing, Life models and, oh yeah, Experience.
COIL OVALITY
Ovality Vs Collapse Pressure
12000 120,000 Psi Yield 69000 lb String Weight
Collapse Pressure (psi)
10000 8000 6000 4000 2000 0 0 1 2 3 4 5 Percent Ovality (%) 2"- .204 Wall
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Collapse Press as Function of YS

0 -2,000 -4,000 0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000
Collapse Press, psi
-6,000 -8,000 -10,000 -12,000 -14,000 -16,000 -18,000 -20,000 70 ksi 90 ksi 110 ksi
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Tubing Load, psi George E. King Engineering GEKEngineering.com
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CT Collapses
CT collapses from a few feet to over 1100 ft have been reported. The problem is that CT is often operated right on the edge of material strength so any disturbance spike (sudden application of load) that can push it to collapse may trigger a collapse in several hundred feet of tube - like a run in hose. Remember, tensile force changes as well unloads?
Worst (?) Cases 1. High annular surface pressure 2. Long CT string 3. Heavy BHA 4. Large diameter BHA 5. Viscous annular fluids 6. Highly ovaled or damaged CT strings or sections 7. Corrosion
Ps
Most severe problem jobs for CT collapse: 1. POOH with any BHA 2. POOH through severe dogleg 3. Fishing (and jar action) 4. Trying to free stuck tubing
Wt Friction
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Collapse
Variables
Strength of CT Condition of the CT - big variances Ovality of CT Size of CT Damage (corrosion, wear, ovality, dents, etc) External pressure (pressure differential) Axial load
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Collapse Summary
Changing variables = moving target. Watch the balance of surface pressure, friction and load. All of these change during the job. Sudden application of load more likely to promote CT collapse than a steady pull Collapse curve accuracy?? Only for round tubes - CT isnt.
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Accuracy Problems
For any constant shape and size piece of pipe, an expression or method of prediction for tension, collapse, or burst can be generated. BUT, CT is a reel of variences handled by a system of extremes. The best we can do are estimations.
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Torsion Yield Strength

Ty = Sy(OD4 - (OD - 2 t wall-min)4)/105.86 OD Where: Ty = Torsion Yield Strength, lb-ft t wall-min = thinnest wall, in Sy = yield strength of the CT, psi OD = CT OD
Torsion Strength for CT Why bother with torsion for CT?

Theoritical Torsion Strength vs CT OD for 0.151" Wall Thickness
Theoritical Torsion Strength, psi
10000 9000 8000 7000 6000 5000 4000 3000 2000 1000 0
1.5
2.5
CT OD, inch
3.5
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Torque
Usually we dont push the torque limit in workovers
need to rotate is very limited smaller motors are very limited in torque output
This changes in CT Drilling, especially with big motors
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TheoriticalTorque Calc. with Round Tube

CT OD (in) 1.25 1.25 1.5 1.75 2 2 2.375 2.875 3.5
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wall (in) 0.07 0.151 0.151 0.151 0.109 0.151 0.151 0.151 0.151
Yield Torque (theory) (psi) (psi) 70,000 488 70,000 864 70,000 1324 70,000 1883 70,000 1956 70,000 2542 70,000 3717 70,000 5633 70,000 8590
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Fillup
Volumes vary with OD and wall thickness Remember, the volume of CT is not just whats in the well - it includes whats on the reel. Friction can be a killer when rates are needed - remember: reel + well.
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Barrels of Fill Up Volume Per 1000 ft of Coiled Tubing (Remember to use entire reel length)
1.8 1.6
1-3/4 1-1/2
Barrels Fill Up per 1000 ft.
1.4 1.2 1 0.8 0.6 0.4 0.2 0 0 0.05 0.1 0.15 0.2 Coiled Tubing Wall Thickness, in.
1-1/4
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Force Application on CT
Force to push CT through stuffing box/stripper (opposite running) Force on CT from Well Head Pressures (upward) Force to overcome friction (opposite running) Force from weight of CT & BHA (downward)
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Other Forces and Loads

Pressure Effects on Length/Force Temperature Effects on Length/Force Stretch Buckling loads
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Swab/Surge Forces
Plunger force - tremendous force exerted event in small movements because of large area affected. Close clearances and high tool movement speeds increase the swab/surge force Circulation while pulling lessens swab/surge loads
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Swab Forces
Problems
small hole volumes
small gas influx causes large underbalance - get in trouble quickly
large BHAs - swab force increased sharply continuous, fast movement of CT horizontal holes
gas storage area - isnt apparent on surface gauge quickly - must monitor trip tanks.
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Swab Effect From Pipe Speed

Hole Size, in.
360
Pipe pulling Speed, fpm

245 167 344 524
180 124 256 394
120 98 192 289
8.5 6.5 5.75

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276 589 921
14 lb/gal mud, 4.5 BHA Adams

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CT Swab and Surge Pressure Effects at BH

Extreme, short duration pressure spikes at BH during CT movement Stick/slip cause???? Aggravated by big/heavy BHA, rough holes Could spot with a trip tank
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CT Stretch - W/Buoyancy Effect

Selastic = 12 L Fbouyancy / A E Where: Selastic= elastic stretch of CT per 1000, in. Fbouyancy = corrected pull on tubing, lb L = tube length (where load applied), ft A = cross sectional area of tubing E = modulus = 30 x 106 psi
Stretch Example for 5000 ft CT With and Without Load

Fluid Weight Length Density Air Wt. Bouyed 2 lb/ft (ft) (lb/gal (lbs) Wt, (lbs) CT OD Wall, in Area, in Added Load (lbs) CT CT Stretch Stretch inches ft
1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25
0.109 0.109 0.109 0.109 0.109 0.109 0.109 0.109
0.391 0.391 0.391 0.391 0.391 0.391 0.391 0.391
1.33 1.33 1.33 1.33 1.33 1.33 1.33 1.33
5000 5000 5000 5000 5000 5000 5000 5000
1.9 1.9 8.33 8.33 10 10 12 12
6640 6640 6640 6640 6640 6640 6640 6640
6447 6447 5794 5794 5625 5625 5422 5422
0 500 0 500 0 500 0 500
33.0 35.5 29.6 32.2 28.8 31.3 27.7 30.3
2.75 2.96 2.47 2.68 2.40 2.61 2.31 2.52
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Fluid Weight Length Density Air Wt. Bouyed CT OD Wall, in Area, in2 lb/ft (ft) (lb/gal (lbs) Wt, (lbs) Added Load (lbs) CT CT Stretch Stretch inches ft
1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5
0.109 0.109 0.109 0.109 0.109 0.109 0.109 0.109
0.476 0.476 0.476 0.476 0.476 0.476 0.476 0.476
1.62 1.62 1.62 1.62 1.62 1.62 1.62 1.62
5000 5000 5000 5000 5000 5000 5000 5000
1.9 1.9 8.33 8.33 10 10 12 12
8095 8095 8095 8095 8095 8095 8095 8095
7860 7860 7064 7064 6857 6857 6610 6610
0 500 0 500 0 500 0 500
33.0 35.1 29.7 31.8 28.8 30.9 27.8 29.9
2.75 2.93 2.47 2.65 2.40 2.58 2.31 2.49
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Fluid Weight Length Density Air Wt. Bouyed 2 CT OD Wall, in Area, in lb/ft (ft) (lb/gal (lbs) Wt, (lbs) Added Load (lbs) CT CT Stretch Stretch inches ft
2 2 2 2 2 2 2 2
0.109 0.109 0.109 0.109 0.109 0.109 0.109 0.109
0.648 0.648 0.648 0.648 0.648 0.648 0.648 0.648
2.20 2.20 2.20 2.20 2.20 2.20 2.20 2.20
5000 5000 5000 5000 5000 5000 5000 5000
1.9 1.9 8.33 8.33 10 10 12 12
11005 10685 11005 10685 11005 9603 11005 9603 11005 9322 11005 9322 11005 8986 11005 8986
0 500 0 500 0 500 0 500
33.0 34.5 29.6 31.2 28.8 30.3 27.7 29.3
2.75 2.88 2.47 2.60 2.40 2.53 2.31 2.44
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CT in Horizontals and Multi-laterals

Buckling loads and estimation of reach Methods of extending reach Examples of CT use
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CT in Horizontal Wells 1. Excellent method for spotting fluids 2. Reasonable method for setting equipment and tools 3. Fair method for unloading
Sticking Points 1. Bend area 2. Lateral

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Max tool length through the bend area.

Max length of stiff pipe or tool L=1/6[R2 - (R - ^d)2]1/2 where: L = tool length, ft R = curve radius, inches ^d = ID casing - OD tool (inches)
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Coiled Tubing BHA

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Coiled Tubing BHAs

George E. King Engineering GEKEngineering.com

CT Well Service Usages

Pre Rig-up Issues

Other Rig-up Notes

External Slip Style Combination - slip and dimpled/setscrews Welded Threaded

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

Coiled Tubing Connectors

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

Internal Slip Style Connectors

External Slip Style Connectors

George E. King Engineering GEKEngineering.com

Other Connection Methods

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

Coiled Tubing Check Valves

George E. King Engineering GEKEngineering.com

Coiled Tubing Check Valves

Flapper check valve assembly

Ball and seat check valve assembly

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

Nozzles and Jetting Subs

Single largediameter port

Muleshoe Angled Jet Nozzle

Multiple smalldiameter ports

George E. King Engineering GEKEngineering.com

Water jets fan out quickly and lose impact force.

George E. King Engineering GEKEngineering.com

Nozzles and Jetting Subs

These tools fall into two categories

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

Bowspring Centralizer used for centralization of tools in fishing in deviated wells.

George E. King Engineering GEKEngineering.com

Loads and Forces

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

George E. King Engineering GEKEngineering.com

Tension failure mode for CT in the laboratory.

Collapse more common than neck down

George E. King Engineering GEKEngineering.com

Axial Load Capacity

Load Capacity Example

Operating Safety Factor Suggestions

0.4 to 0.5 for corroded strings

An anode can start here or here. Base metal