API Standards for Coiled Tubulars

API Standards for Coiled API Standards for Coiled TubularsTubulars

Roderic K. Stanley, Ph. D, I. Eng. SPE

International Oilfield ServicesInternational Oilfield ServicesChm: API Resource Group for Coiled Tubing

[email protected] Nov 05Aberdeen Nov 05

Coiled Tubulars?Coiled Tubulars?•• Coiled Tubing (CT)Coiled Tubing (CT) - small dia – 4.5-in. ERW

carbon steel tubing used in numerous ways• CT55, CT70, CT80, CT90 (in RP 5C7)•• Coiled Line Pipe (CLP)Coiled Line Pipe (CLP) – small dia – 6.625-in.

ERW carbon steel tubing used as umbilicals, flowlines, etc.

• X52C, X56C, X60C, X65C, X70C, X80C –follow the 5L classifications for line pipe

•• Currently Currently ExcludesExcludes: short welded lengths of ERW and smls.

SPESPE--IcotaIcota--Aberdeen Nov 05Aberdeen Nov 05

CT and CLPCT and CLPNote..From 1944

A cycle here is not…..

Coiled Coiled TubingTubing

CLP

From 2000

CLP…a cycle here…a cycle hereCoiled line Pipe SPESPE--IcotaIcota--Aberdeen Nov 05Aberdeen Nov 05

A Little Background…..A Little Background…..


Where we were in 1998…….Where we were in 1998…….•• ResourceResource GpGp. for Coiled Tubing formed 1996. for Coiled Tubing formed 1996•• SPE 46019 “SPE 46019 “Progress Towards API Specifications for Progress Towards API Specifications for

Coiled Tubing and PipeCoiled Tubing and Pipe” by ” by SasSas--JaworskiJaworski/Stanley/Stanley•• Working on Working on RP 5C7RP 5C7 –– “catch all” RP “catch all” RP –– one of a kind.one of a kind.•• Working on Working on Spec 5LCPSpec 5LCP –– Coiled Line Pipe thought to Coiled Line Pipe thought to

be very importantbe very important•• Working on Working on Spec 5STSpec 5ST -- Coiled Tubing Spec was Coiled Tubing Spec was

shelved in order to get 5LCP into print.shelved in order to get 5LCP into print.•• Approved Approved ––to work on to work on RP 5C8RP 5C8 (Care, Maintenance (Care, Maintenance

and Inspection of Coiled Tubing*) and Inspection of Coiled Tubing*) * Later changed to * Later changed to “Coiled Tubulars”“Coiled Tubulars”


Current API OrganizationCurrent API OrganizationSPESPE--IcotaIcota--Aberdeen Nov 05Aberdeen Nov 05

You are here

Fun stuff here

Kinda wild here too

And we are in here too

The new guys on the block

CT CLP

API representation API representation -- todaytoday•• PurchasersPurchasers: Service Companies, Major Oils,

Pipeliners. •• OperatorsOperators: Major Oils•• Mills:Mills: Manufacturers.•• ConsultantsConsultants: Welding, Collapse•• ObserversObservers: MMS, DoT, Rosen, Sumitomo•• InspectionInspection: Tuboscope, Patterson (RD/Tech),

Intl. OilFld Svcs•• API:API: attend all meetings


Current Documents Current Documents -- 5C75C7


• API RP 5C7 – CT55-90 only (1996)

• Tensiles beforebefore bending• Renewed 2001• Remain in force until

either updated or withdrawn

• Operational sections transferred to a Committee 6Committee 6 document on well servicing

• Corrosion and Collapse transferred to RP 5C8

Current Documents Current Documents –– 5LCP (1999)5LCP (1999)• Converted from 5L (41st Ed)• Dropped all mfg except ERWERW• Added SkelpSkelp--end weldend weld, NDE NDE

not in 5Lnot in 5L, 15 min hydro at 15 min hydro at 80% SMYS,80% SMYS, butt welding to butt welding to API 5L/1104API 5L/1104, tensiles at “mill stops”.

•• Charpy testsCharpy tests at customer request.

• Can class CT55CT55--8080 as X52CX52C--X80C. (No X42C)X80C. (No X42C)

•• Up for 5Up for 5--yr reviewyr review


In the Works…In the Works…API Spec 5STAPI Spec 5ST

(Specification for Coiled Tubing)

•• ((5LCP pbl conv to CT))• Was Voted in 2001• Not enough votes• “Not tight enough”• Put on hold • Pressure to re-introduce

in 2003• New chm. found 2005• Work to begin now

API RP 5C8API RP 5C8(Care, Maintenance, Inspection of Coiled Tubulars)

•Grades up to CT110

•Mechanicals, inc CSA, defect removal definitions

•Corrosion & Mitigation

•Butt Welding and its NDE

•Tube NDE – Visual/Dimensional

EMI, Prove-Up

• Assessment of Used CT

• Collapse from 5C7 into Appendix

• Defect Pictures in appendixSPESPE--IcotaIcota--Aberdeen Nov 05Aberdeen Nov 05

Why RP 5C8?Why RP 5C8?• Repeated and unidentified field failures

• Provide minimum requirements for field protection of C-Tubulars

•Provide field welding procedures

•Provide field general NDE procedures for common EMI EMI systems.

•Provide NDE equipment standardization/calibration requirements

•Aim to replace RP 5C7

COILED TUBING FAILURES 1987-98

0

10

20

30

4050

60

70

80

90Corro

sion

Rig Opera

tions

Manufactu

ring

OD wea

rTens

ileButt W

eld

OC

CU

REN

CES


Corrosion and Corrosion and MitigationMitigation

Pits/cracks on OD→

Pitting at root of flash column, + crack


Mitigation and PreventionMitigation and Prevention• Flushing – high pH

fluids• OD Cleaning and

coating• ID Cleaning and coating• Air drying• N2 dry and backfill• Relative Humidity of

flush/backfill measurement

• Dew point measurementRH meter


http://www.omega.com/ppt/pptsc.asp?ref=HH313_314&nav=temhu02

TubeTube--Tube Butt Welding……..Tube Butt Welding……..• Industry welding sub-

committee formed• WPS and PQR contents

established• Manual and Orbital butt

welds• ..not ADB or other exotic

methods• Borrowed material from

Icota Welding document

Bonded interface

400μm

Amorphous Bond in CT


………….and its NDE………….and its NDE

Phased array weld inspectionGeometry considerations


16 element linear array Sweep from 40 to 70 degrees

Status today……Status today……5LCP 5LCP –– voted late 2004voted late 2004•• changeschanges out for vote• Added more ultrasonic

NDE, esp for butt welds• Add X90CX90C grade• Provide for torch-cut

ends• Reduce acceptable min.

wall from ––12.5%t12.5%t to ––10%t.10%t.

RP 5C8 RP 5C8 –– Voted late 2004 Voted late 2004 • changeschanges out for vote• more “shoulds” and no “shalls”. • Added definitions of “cycle” and “critical sour well“ (AEUB)• Added pictures of common defects in an appendix


Status today..(2)2)PSLs might includePSLs might include

•Additional UT of SE weld

•Additional UT of Butt weld

•Restricted tensile ranges (for sour service)

•Restricted hardness ranges (same)

•Additional microhardness readings

• Final NDE Inspection after hydro

• Longer/higher pressure test

5ST5ST• Chm. found midyear• Cover mfg, grades,

testing, inspection• Include Product

Service Levels?


5C8 5C8 -- Equipment Equipment Standardization & CalibrationStandardization & Calibration

From RP 5A5…….• All equipment calibratedcalibrated at regular intervals• All equipment standardizedstandardized at regular intervals• Reference standards & reference indicators

maintained.• EMI unit, UT Compression wall gauge, UT shear

wave unit, RT unit, Mag. particle yokes, pit depth gauges.

• All Operators trained, qualified and certified


Examples Examples -- CalibratableCalibratableEquipmentEquipment

EMI equipment for full length CT inspection – now defunct UT Butt weld inspection

equipmentSPESPE--IcotaIcota--Aberdeen Nov 05Aberdeen Nov 05

Tubing Tubing Assessment Assessment TableTable--5C85C8

Classified sections of tubulars from TFL and NDE, not just either one


What Do You Do When You Find What Do You Do When You Find an Imperfection?an Imperfection?

• Need to notify owner of tubing

•Check the inspection table

• Use a Fatigue model

•Make assessment including fatigue model and defect size

•Repair the damage SPESPE--IcotaIcota--Aberdeen Nov 05Aberdeen Nov 05

5C8 Appendix5C8 Appendix


Training and Certification 1Training and Certification 1• All Inspectors qualified and certified…..• Use ASNT Scheme (TC-1A or CP-189)• 0r PCN Scheme• Level 1• Level II• Level III• In EMI, UT, MT, PT, RT• Nonlevelled courses in Visual, Dimensional and

Hardness Testing


Training and Certification 2Training and Certification 2Inspector should be;Inspector should be;

1. Trained in all inspections used on CT/CLP

2. T/C to Level II under ASNT or PCN regime

3. Cognisant of accept/reject/derating criteria

4. This implies that the SpecificSpecific part of the certification exams should cover knowledge of the equipment used, and the accept/reject criteria.


Typical Training Course Typical Training Course OutlineOutline

• Coiled Tubulars• Fatigue Models• Common defects• Effect of defects• PT course (G, S, Pr)• RT course (G, S, Pr)• UT course (G, S, Pr)• MT course (G, S, Pr)• EMI course (G, S,Pr)

• Visual Inspection

• Hardness Testing

• Other, as needed

Similar to classes Similar to classes developed for DSdeveloped for DS--1 1 or NSor NS--22


Collapse in RP 5C8Collapse in RP 5C8• Moved from bodybody of 5C7 to AppendixAppendix of 5C8• Added disclaimer regarding origin of collapse

equations for new and used coiled tubing


Collapse appendixCollapse appendix•Vast amt of high level work done on new/old tubular collapse data

•New equation developed for API 5C3/ISO 119400

•Eliminates 4 equations for Yield strength, plastic, transition, and elastic collapse regimes

•Replaced them with one (more complex) equation

•Tamano 4, generalized by Dr. Frans Kever ( KGT)

• Work yet to be defined for normalized ERW tubing SPESPE--IcotaIcota--Aberdeen Nov 05Aberdeen Nov 05

Possible new API RGCT Possible new API RGCT Approach…..Approach…..

• Obtain results from KGT (2000 data points), which includes all data points at higher measured values for concervatism.

•Use results for more roundedmore rounded Stress-strain curves

•Add existing Avakov-Timoshenko correction for OvalityOvality

•Add existing Avakov correction for coiled tubing usageusage

This is the same approach as was used to generate the original This is the same approach as was used to generate the original values in 5C7, but there, the old equations from 5C3 were values in 5C7, but there, the old equations from 5C3 were used. Here, we place them with KGTused. Here, we place them with KGT


The equations……CollapseThe equations……Collapsepc,ult = (pe+py)/2 – [(pe-py)2/4 + pepyHult]1/2 (A1)

Where

pe =1.08[2E/(1-ν2)][(Do/t)-1 (Do/t - 1)-2] (A2)

py = 2fy[Do/t – 1][Do/t]-2[1 + 1.5/(Do/t –1)] (A3)

Hult = 0.071Ov + 0.0022 ec – 0.018 rs (A4)

And

Do = actual average diameter, E = Young’s Modulus

ec = eccentricity in % as (tmax-tmin)/tav fy = Actual API Yield stress.

Hult = is a decrement factor Ov = Ovality% as (Do,max-Do,min)/Do,av

pc,ult = Ultimate collapse str, pe = Collapse str for elastic elastic failure

py = Collapse str for yieldyield failure, rs = Residual stress

t = Average wall thickness ν = Poisson’s ratio.SPESPE--IcotaIcota--Aberdeen Nov 05Aberdeen Nov 05

Collapse Collapse DesignDesign EquationsEquations

pc,des = (kepe+kppy)/2 – [(kepe-kppy)2/4 + kepekppyHdes]1/2 (A5)

where

Hdes = Decrement factor (varies with manufacturing process).

ke = Downrating Factor for elastic collapse

kp = Downrating Factor for plastic collapse.

One challenge is to define H for a coiled tubular. Is thevalue for normalized, not hot/cold straightened applicable?
