Nondestructive evaluation (NDE) of new and in-service CT is leading to higher quality (conformance to specifications), the driver being high pressure, high temperature service work. This paper outlines a number of "firsts" in NDE that have occurred at Quality Tubing. We have installed and operated an electromagnetic strip inspection device and removed many strip surface imperfections, and a phased-array ultrasound (PAUT) system for weld-seam/heat-affected zone (HAZ) inspection of new tubing for the detection of typical seam anomalies. In order to inspect butt-welds quickly and without radiation, we are investigating the use of ultrasound, and have also procedurized bias weld and seam weld prove-up procedures using UT. Further, we have "final-inspected" (i.e. NDE after hydrostatic test) numerous strings for many coiled line pipe (CLP) projects, and more recently "high-exposure" coiled tubing projects such as Sakhalin, Thunderhorse projects.

For used materials, we have NDE-inspected for cement plugs, weld locations, and typical used-tubing defects, and have assisted in the determination of API derating criteria for in-service materials.

Recently, an untethered robot, capable of inspecting CLP/CT has emerged, and is introduced here.


In earlier papers we have introduced overviews of NDE improvements that have been made regarding strip and tubing inspection.1,2 Here we also discuss these and other NDE procedures that we have used in a variety of situations, and often for the first time in this industry. The motivating factors have been:

  1. studies of in-house and field failures in CT 3,4,10

  2. the need to minimize the potential for imperfections entering field service,

  3. the need to assess the remaining life of in-service coiled tubing, so as to provide for better risk analysis on the part of the owners of the tubing and the well 11,12,

  4. the need to set some rules for in-service inspection 13.

Historically, solutions have emerged from needs to perform the following:

  1. Inspect new coiled line pipe (See API 5LCP) and then coiled tubing (CT) after hydrostatic test. This need is currently met by the use of a conventional oilfield tubular (EMI) inspection unit.

  2. Inspect the newly-formed strip bias welds more thoroughly than can be accomplished by radiography (RT). This need is met by the use of shear-wave ultrasound.

  3. Inspect the strip itself thoroughly from end to end, in order to detect imperfections caused by the strip manufacturer, the slitter, and transportation /handling.

  4. Inspect the HFI weld more thoroughly than can be accomplished by the conventional eddy current methods. This need is met by ultrasonic weld-line inspection.

  5. Inspect butt welds in CT and CLP by a single-wall method (UT) rather than by a double-wall method (RT) in order to achieve sensitivity to planar weld defects.

  6. And finally, the need to begin to define unacceptable conditions in both CLP and CT products.

In this paper, we deal with the new tubing NDE issues in the order in which they occur in the manufacturing flow, then comment on the in-service inspections that we have performed, and finally outline where the industry stands in relation to tying fatigue and NDE data into one package that will provide for a good assessment of present state of coiled tubing. These include

  1. Detecting internal anchor locations in CT (See Fig. 18).

  2. Detected butt welds in high-Cr.seamless coiled materials (See Fig. 18).

  3. Detected the locations of cement inside CT (See Fig. 9)

  4. Searched for flat spots caused by residual bend and tubing buckling (See Fig. 9).

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