WHAT’S IN YOUR COILED

TUBING?

Roderic K. Stanley, Ph D, I. Eng Rkstanley@ndeic.com

ItRobotics, Inc., Stafford, TX

International Oilfield Services

Icota Lunch and Learn, February 8, 2011

Coiled Tubing Resources Management

A New Coiled Tubing Assessment System

• Coiled tubular assessment systems are available from itRobotics. Service available from Int’l Oilfield Services

• The system measures wall parameters and detects imperfections.

• The inspection head of the system is a “clamshell”, so that only certain regions of a CT reel can be inspected if needed.

• The effect of OD surface imperfections can be assessed by the use of the Flexor TU06 fatigue model from the U of Tulsa. They can then be removed as needed.

• The system meets the requirements of SR 37 in API 5ST (Specification for Coiled Tubing) for “inspection after hydrostatic test”. Thus it can be used to set baseline data at a CT mill.

• The system can be used in the field, so that the degradation of a string during its lifetime can be assessed.

ItRobotics, Inc 12841 Capricorn Street

Stafford, Texas 77477-3912 281-313-7900, 281-313-7901 fx Not Zone 1 yet, but

electronics are potted

Head, Closed • Length counter wheel • Permanent Nd-B-Fe magnets provide the

saturated longitudinal field induction in the tubing.

• 4 “shoes” in stainless steel housings contain multiple hall-effect sensors ring the tbg.

• The tangential (Bx) and normal (Br) external field strength is measured close to the tubing surface to detect imperfections and measure wall thickness.

• An eddy current lift-off technique (8 sensors) is used for diameter measurement and ovality computation.

• The tube is longitudinally magnetized. • If butt welds are needed, the 2 ends should

be demagnetized. • Sizes 1.25, 1.50. 1.75, 1.00, 2.375. • Size change is easy.

Nd-Fe-B magnets

Signal cable attach

Head Dimensions The tube diameter is measured at 8 places, and the ovality of the tube is computed from these readings.

Θ = Dmax – Dmin x 200

Dmax + Dmin

Rings of hall-effect sensors between the poles of the magnets measure the wall thickness and detect imperfections and defects.

The system can back over suspected signals and over-write the inspection record as a check that signals are real.

Performing Standardization

• Here the unit is being standardized on a reference standard that meets the ExxonMobil & API 5ST requirements.

• The standard contains 10% LID, LOD, TID and TOD EDM reference notches, 1/32nd in. TDHs, & wall thickness reduction.

MFL from OD flaw

MFL from ID flaw

Computer Screen, 1.75 x 0.134-in. tbg

• As part of prove-up, any area of this “standard” screen can be expanded so as to “focus in” on each of the signals. The vibration sensor also helps discriminate real signals from tubing vibrations. And the data can be over-written to prove it was real.

Speed

ButtWeld

Weldline MFL

Lamps light when MFL signal in octant, make imperfections easy to find during prove-up

Scales show tube dimensions

Wall loss Area TID TOD 1/32

TDH

LID LOD

Notepad

Expandable Length Counter- this one is set for 25 ft

360 degree map

Variable Alarm Thresholds

Max, Min and average wall plotted

Max, Min and average OD plotted

Ovality, Diameter, & 4 runs on a Reference Standard

• Reference standard is rotated 90° between runs so as to verify the uniformity of sensitivity.

• This is commonly done in OCTG inspection standardization.

• This simulation shows OD, wall and ovality at any location down the tube, in real time.

• When the red button is pushed, the diameter and wall thickness measurements appear.

• X- and Y- axes show measured dimensions.

• Wall thickness is the value computed from the tangential hall effect signal readings. (There is no contact with the tubing, so none of the problems that are associated with ultrasonics).

• Data are stored every 0.5 inch because diameter and ovality do not change very rapidly.

Zoomed MFL

signals 1 • Areas of the maps can

be zoomed for more detail, and possible signal recognition.

• This is done by stop-ping the inspection, or later on, depending upon where the ins-pection is performed.

• This is because this part of the programme takes a short while to load

Longitudinal notch

Transverse notch

Signals from all 4 “shoes”

Length of flaw can be measured

Rotatable 3D MFL map

Digitized (every 0.5 mm) MFL signals

• By rotating the 3D map, the peaks of the longitudinal EDM notch measure its length.

• There is MFL from the ends of LOD and LID notches. • Observe the difference in signal shape between the longitudinal

and transverse notches.

Zoomed MFL 2 - Longitudinal EDM Notch 0.020-in. wide (API 5ST SR37)

• There is only MFL from the beginning and ends of EDM notches

• There is MFL in at least 3 sensors. • Note the regularity in the magnetic

noise all the way around tube. (I am not sure what caused this; maybe magnetic permeability variations.)

Ends of EDM notch

degrees

Gauss

Ends of 0.50-in LOD-notch • End signals indicate the length of the

notch, in this case 0.5-in. • Recall that the magnetic field is

parallel to the notch but we still have a 40 G swing peak-to-peak.

• 3 sensors (blue green red), have detected MFL from LOD notch (upper trace).

1/32nd Through-drilled Hole

Peak-to-peak amplitude is 80 G

One or more of these will show in red when a MFL signal passes through that octant, making internal flaws easy to locate

Hole is picked up on more than 1 sensor

Window length is 15 ft

Butt Weld Typical Butt Weld

MFL signal

Variability of MFL around the weld

Very large 500 Gauss signal

• The BW is picked up all the way around the pipe.

• Its 4-peaked structure is typical of these welds

• This MFL signal shows that a trans-verse crack in a BW might be hard to find, and they need to be reinspected with Ultra-sound for cracks . (UT is single wall, RT is double –wall)

• Location of butt welds is critically important in used tubing

• These make excellent markers.

Signals Taken on New Tubing • The following

signals were collected on new coiled tubing.

Roll-in Near Seam Weld

Signals from 75 sensors on a seam weld inspection unit with the flux density, ( B )at 45 deg to the longitudinal seam weld and to the axis of the tube.

Skelp End Weld 19350-ft. along Tube

Start

End

Recognizable by variable MFL at 45 deg around tube

Seam weld

Seam Weld

Variable Long Seam Weld Noise • Data from

12,600-ft of a string

• High seam weld MFL noise from internal flash column on several strips.

• One step-taper visible.

• OD is show-ing a little ovality in the last 2 (thinner-wall) strips.

MFL from Δt

One Source of MFL Noise • A 3D look at one indication

at 1298-ft. in this string, has a peak-to-peak amplitude of 140 Gauss.

• This is part of the prove-up procedure and aids the observer in flaw recognition.

• The cause was a piece of “spume”, found by mill RT.

Shape of signal indicates whether MFL comes from excess metal or a pit.

New Tubing Stored for 3 Years.

OD surface pitting in new tubing at 13,085-ft.

Almost full length round-bottomed pitting was found on the OD surface of a new string that had been stored in Houston for 3 yrs and indicates the need for a good maintenance programme since current protective coatings do not appear to last long. The pits have a maximum depth of 0.018-in. (8.5% of measured wall, 0.204-in).

MFL Image of a row of pits in the OD of stored pipe.

The 3-D picture enables determination of location and thus determines where to scan with ultrasound or radiography if they were to originate from mid-wall or ID imperfections.

Analysis of Deepest Pit • To assess the possible effect of

this OD pitting, Flexor TU was used to generate the trips to crack initiation and failure, and the 95% confidence level in the initiation calculation for this grade (CT110) and size, an internal pressure of 3 kpsi, and a 42-in. radius reel (See Table ).

• The pits were not removed, and this small wall loss was not considered by the owner to be sufficient to seriously affect the fatigue performance of the tubing, which is in line with the results of research performed at the U of Tulsa. Measuring the dimensions of the worst pits and using them in Flexor indicates the difference in calculated fatigue life that these flaws can create.

: Flexor TU 6.1 calculations. New CT Pit

Trips to… none present removed

Initiation of crack 187 176 181

Failure 222 209 215

95% confidence 151 88 119

• The wall thickness data for this string are shown with the vertical scale expanded. There are 3 continuously tapered sections, and the skelp-end welds can be seen because of their MFL. This weld MFL provides markers for determining length changes.

Chafing Marks and Gouges • Chafing Marks: Larger and heavier

CT can be chafed against the sides of the storage reel, as shown here.

• This one was 0.013-in. deep and removed by mill staff prior to shipping the string, with the final tubing wall thickness meeting API wall thickness tolerance.

• A second example of multiple chafing marks.

• It has now become standard practice to remove such shallow marks by buffing, since removal maximizes the remaining fatigue life at that point.

Signals from Used Tubing • The notched reference standards are

used to set up (standardize) the instrument on NEW tubing at the mill, or as “receiving inspection” at a client’s yard.

• When inspecting USED tubing we would normally set up on a 1/16th-in. TDH or partial hole, and a 10% wall loss area.

• We can classify various sections of tubing according our own or customer requirements.

First, Why We Did Not Use UT • UT requires very clean smooth entry & exit

surfaces, so serious cleaning is required. • Surfaces of used tubing are generally

covered with rust or other materials that do not transmit ultrasound.

• Even the small amount of rust shown also affects the eddy current lift off sensor response.

• Recall that there is always the potential that the rust may contain naturally occurring radioactive scales (NORM). NORM).

Results of Field Acid Job • This 1.25-in. string has done an acid job in

LA, & lost some wall thickness at the bottom end. We took out some OD gouges to about 10% t so as to raise the fatigue life. We recommended that the bottom 2000-ft be removed since wall had fallen from 0.156-in. to 0.122-0.125-in.

Three views of imperfection MFL signal found near to seam weld at 12500-ft. and removed by sanding.

OD Gouges at 11,630 ft & 12.468-ft • Gouge close to seam weld. • These gouges may be caused going

into the hole. • A very small scratch all the way

around the tube. • Note that seam weld noise is very low

here

A 2nd gouge near to the seam weld. The seam weld noise appears to come from regularly- spaced small spume mushrooms on the ID.

2.375-in. CT100 string • This used string showed surface

gouges of maximum depth 0.015-in.

Longitudinal rows of pits were also found.

Ovality as much as 8% was measured on this string.

Dents in Same String • String also showed dents that

were caused by pressure against spokes in service reel.

• MFL from dent

Bias Weld MFL Signal in Field • Bias and butt welds make

good markers, and can be used to determine real lengths and local stretch.

• The first skelp-end (bias) weld off the reel makes a good origin of length coordinates

• This magnetic noise from these welds was measured on the previous job

• Often there is more magnetic noise nearer to the 45º corners of these SE welds.

Signal Prove Up • Finally, signals are proved up. • Conventional dimensional (caliper, UT Compression

wave, ruler, pit gauge) measurements for OD surface imperfections.

• UTCW for ID pitting • UT Shear Wave for 2-Dimensional (crack-like)

defects • And, of course, the expanded 3D MFL signals

themselves. • When assessing new tubing, the mill can perform

Radiography (RT) if needed. • All of these prove-up techniques have been laid out

in earlier SPE and Icota publications, and are standard procedures for assessment of tubing

Compression wave unit

Phased array shear wave

Imperfection Assessment • We have given a lot of thought to what an imperfection does to

tubing when it is bend-cycled and is accumulating fatigue. • Some CT fatigue models exist that do not take into account the

effect of imperfections and defects.

ID cracks – black light

So we have added Flexor TU (from the University of Tulsa) into the laptop. This programme contains the detrimental effect of imperfections and defects, so that quantitative decisions regarding removal can then be made.

Imperfection Removal for CT • We can assess the severity of OD surface imperfections using Flexor

TU06. • We can remove the imperfections so as to leave the minimum specified

wall (API, Client) in tact (new tubg) or help to raise the remaining life (used tubg).

• We can perform compression wave wall measurements to check remaining wall thickness after flaw removal.

• We can also perform shear wave inspection on bias, butt and seam welds.

• We provide an inspection report that can be used as the basis for future inspections.

Conclusions

• A CT inspection and assessment system is available from itRobotics, and in service at IOS-PCI.

• The system measures wall thickness and OD, computes ovality, and detects imperfections and defects at specific locations on tubing.

• The system also detects welds, which act as excellent markers • Some prove-up can be performed using the MFL images, and

some will be done when the tool is stopped for a second look at the tbg.

• ….and this is just the beginning! • This MFL programming is retrofittable to conventional OCTG

MFL units